APMP Supplementary Comparison on
Fiber Optic Power Responsivity
APMP.PR-S2
Final Report
Seung Kwan Kim, Dong-Hoon Lee, and Seung-Nam Park
Division of Physical Metrology, Korea Research Institute of Standards and Science
267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340, Republic of Korea
Correspondence to: [email protected]
APMP.PR-S2 Fiber Optic Power Responsivity
APMP Supplementary Comparison on Fiber Optic Power Responsivity
Seung Kwan Kim, Dong-Hoon Lee, and Seung-Nam Park
Division of Physical Metrology, Korea Research Institute of Standards and Science
267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340, Republic of Korea
[email protected]
Abstract
KRISS, NMISA, CMS/ITRI, NMC-A*STAR, NMIJ/AIST, NMIA, NML-SIRIM, NIM, and
VNIIOFI conducted a supplementary comparison on the fiber optic power responsivity at 1310
nm and 1550 nm. The aim of this comparison is to examine the equivalence of the fiber optic
power responsivity among participating laboratories and to provide supporting evidence for
associated CMC claims in BIPM KCDB.
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APMP.PR-S2 Fiber Optic Power Responsivity
Table of Contents
1.
Introduction ........................................................................................................................... 4
2.
Organization of the comparison ............................................................................................ 5
2.1.
Participants .................................................................................................................. 5
2.2.
Participants’ details ..................................................................................................... 5
2.3.
Form of the comparison .............................................................................................. 7
2.4.
Timetable..................................................................................................................... 8
3.
Description of the artifact .................................................................................................... 10
4.
Measurement Capability and Results of Pilot Laboratory ................................................... 13
5.
6.
7.
4.1.
Traceability ............................................................................................................... 13
4.2.
Description of measurement facility ......................................................................... 14
4.3.
Laboratory conditions ............................................................................................... 16
4.4.
Measurement procedure ............................................................................................ 16
4.5.
Measurement results ................................................................................................. 17
4.6.
Uncertainty ................................................................................................................ 18
Measurement Capabilities and Results of Participants ........................................................ 21
5.1.
NMISA ...................................................................................................................... 21
5.2.
CMS/ITRI ................................................................................................................. 28
5.3.
NMC-A*STAR ......................................................................................................... 31
5.4.
NMIJ/AIST ............................................................................................................... 39
5.5.
NMIA ........................................................................................................................ 56
5.6.
NML-SIRIM ............................................................................................................. 73
5.7.
NIM ........................................................................................................................... 76
5.8.
NIM (Second Measurements) ................................................................................... 80
5.9.
VNIIOFI .................................................................................................................... 84
Results and Discussions ...................................................................................................... 87
6.1.
Artifact Drift ............................................................................................................. 87
6.2.
Difference from Pilot ................................................................................................ 90
6.3.
Comparison Reference Value .................................................................................... 94
6.4.
Degree of Equivalence .............................................................................................. 99
6.5.
Discussions.............................................................................................................. 103
Conclusions ....................................................................................................................... 105
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APMP.PR-S2 Fiber Optic Power Responsivity
1. Introduction
Under the Mutual Recognition Arrangement (MRA) the metrological equivalence of national
measurement standards will be determined by a set of key comparisons chosen and organized by
the Consultative Committees of the CIPM working closely with the Regional Metrology
Organizations (RMOs).
At its meeting in November 2004, the Technical Committee for Photometry and Radiometry
(TCPR) of the Asia Pacific Metrology Programme (APMP) proposed several regional
comparisons in the field of optical radiation metrology. Fiber optic power responsivity was one
of them and was agreed to be conducted as supplementary comparison.
The present report concerns the supplementary comparison APMP.PR-S2, international
comparison of fiber optic power responsivity measurements at the wavelength of 1310 nm and
1550 nm, piloted by KRISS. The technical protocol was prepared by KRISS and agreed by all
the other participants. The comparison was carried out through the calibration of a fiber optic
power meter chosen as the comparison artifact. The comparison was organized in a star format
as [pilot]-[participant]-[pilot].
The comparison measurement began in January, 2006 with eight participants. While
measurements were being carried out, VNIIOFI joined under the agreement by all participants.
It was agreed that VNIIOFI’s result would be added in the appendix of the report in order not to
affect the original comparison schedule. However, measurements were delayed due to several
unexpected reasons even after VNIIOFI’s participation. Therefore, VNIIOFI’s result was also
included in the report since all the reports from participants including VNIIOFI were available
at the time of report preparation.
For more details, the Technical Protocol of the APMP.PR-S2 comparison can be referred.
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APMP.PR-S2 Fiber Optic Power Responsivity
2. Organization of the comparison
2.1. Participants
The participants of this supplementary comparison were: KRISS (Republic of Korea), CSIRNML (now NMISA, South Africa), CMS/ITRI (Chinese Taipei), SPRING (now NMC-A*STAR,
Singapore), NMIJ/AIST (Japan), NMIA (Australia), NML-SIRIM (Malaysia), NIM (People’s
Republic of China), and VNIIOFI (Russia); KRISS acted as the pilot laboratory.
All the participants were able to demonstrate traceability to an independent realization of the
quantity or make clear the route of traceability to the quantity via another named laboratory at
the time of comparison measurements.
2.2. Participants’ details
Table 2-2-1. Contact list of participants.
NMI Name
(Country)
Personnel
KRISS
(Republic of Korea)
Seung Kwan Kim
Seung-Nam Park
NMISA
(South Africa)
Bertus Theron*
Mariesa Nel
Natasha NelSakharova
CMS/ITRI
(Republic of China)
Min-Jay Huang*
Mao-Sheng Huang*
Hsueh-Ling Yu
NMC-A*STAR
(Singapore)
Huang Xuebo
Xu Gan
Contact information
Center for Photometry and Radiometry
Division of Physical Metrology
Korea Research Institute of Standards and Science
1 Doryong-dong, Yuseong-gu
Daejeon 305-340, Republic of Korea
Tel:
+82 42 868-5701, 5200
Fax:
+82 42 868-5022
E-mail: [email protected]; [email protected]
Fiber Optics Laboratory
National Metrology Institute of South Africa
Private Bag X34, Lynnwood Ridge, 0040
South Africa
Tel:
+27 12 841 2561, 3618
Fax:
+27 86 509 6171, +27 12 841 2131
E-mail: [email protected];
[email protected]
Center for Measurement Standards, ITRI
321 Kuang Fu Rd., Sec. 2, Bldg. 16
30042 Hsinchu, Taiwan, R.O.China
Tel:
+886 3 5743746
Fax:
+886 3 5716231
E-mail: [email protected]; [email protected]
National Metrology Centre
Agency for Science, Technology and Research
(A*STAR)
1 Science Park Drive, Singapore 118221
Tel:
+65 6279 1939, 1937
Fax:
+65 6279 1995
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APMP.PR-S2 Fiber Optic Power Responsivity
E-mail:
NMIJ/AIST
(Japan)
Kuniaki Amemiya
Terubumi Saito*
NIMA
(Australia)
Errol Atkinson
Philip Lukins*
Peter Manson
NML-SIRIM
(Malaysia)
Mohd Nizam
Abdullah
NIM
(People’s Republic of
China)
Lin Yandong
Zhang Zixin
VNIIOFI
(Russia)
Alexey Svetlichny
Vladimir Kravtsov
[email protected]
[email protected]
Laser Standard Laboratory
NMIJ
Tsukuba Center 3-9, AIST
1-1-1 Umezono, Tsukuba 305-8563, Japan
Tel:
+81 29 861 4191
Fax:
+81 29 861 4259
E-mail: [email protected]
Optical Standards
National Measurement Institute
Department of Innovation, Industry, Science and
Research
Bradfield Road, West Lindfield NSW 2070, Australia
Tel:
+61 2 8467 3858
Fax:
+61 2 8467 3752
E-mail: [email protected]
[email protected]
National Metrology Laboratory
SIRIM Berhad
Lot PT 4803 Bandar Baru Salak Tinggi
43900 Sepang
Selangor Darul Ehsan, Malaysia
Tel:
+603-87781644
Fax:
+603-87781616
E-mail: [email protected]
Optical Measurement Division
National Institute of Metrology
18 Bei San Huan Dong Lu
100013 Beijing, China
Tel:
+86 10 64218651
Fax:
+86 10 64218651
E-mail: [email protected]; [email protected]
Laboratory of low-intensity laser radiation and fiberoptical systems metrology
All Russian Research Institute for Optical and Physical
Measurements (VNIIOFI)
46 Ozernaya street, Moscow 119361, Russia
Tel:
+7 495 7814587, 7814586
Fax:
+7 495 7814587, 4373147
E-mail: [email protected]; [email protected]
* Their affiliation changed and they are not related with this work any longer.
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APMP.PR-S2 Fiber Optic Power Responsivity
2.3. Form of the comparison
The comparison was carried out through the calibration of a fiber optic power meter prepared by
KRISS. A detailed description of the fiber optic power meter used in this comparison is given in
section 3. The fiber optic power meter consists of an optical head, a unit for control and display,
and an electrical cable connecting them. KRISS further prepared two FC/PC type fiber optic
patch cords labeled as FC-1 and FC-2 to reduce the uncertainty from using different kinds of
fiber optic connector. FC-2 was prepared only in the case that FC-1 would be damaged. FC-1
had been used without any problem throughout the measurements and therefore FC-2 was not
actually used for comparison. It was recommended that the participants would report the
measurement results both with the prepared fiber optic patch cords and with their own patch
cords in order to investigate how large the deviation could occur owing to the use of different
fiber connector.
The comparison was organized in a star type format. KRISS calibrated the artifact first and
then sent it to a participant. The participant calibrated it and returned the artifact to KRISS.
KRISS re-calibrate it to check the drift during the period of transportation and measurements in
a different country. The process was repeated until all the participants finished their calibration.
It was agreed that each participant should report its correction factor at 1310 nm and 1550 nm
at the radiant power level of -10 dBm (0.1 mW), and it was strongly recommended that the
correction factors at the radiant power level of -20 dBm (0.01 mW), and -30 dBm (0.001 mW)
be reported if available.
In addition, it was agreed that each participant should specify the type of the optical source
used, center wavelength with uncertainty defined in the technical protocol, and FWHM.
Finally, it was agreed that it is the participants’ responsibility to report the actual wavelengths
used, corrections to be made to the measurement results for the center wavelength offsets and
uncertainties associated with such corrections. The participants should make corrections based
on the spectral responsivity data of the transfer power meter determined by its own means.
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APMP.PR-S2 Fiber Optic Power Responsivity
2.4. Timetable
Timetable of the original plan of the comparison as given in the technical protocol is shown in
Table 2-4-1.
Table 2-4-1. Scheduled timetable of the comparison in the beginning.
Activity
Circulation of technical protocol and invitation of participants
Confirmation of participation and revision of protocol
Submission of technical protocol to TCPR chair for approval
Final revision and announcement of kick-off
Calibration of NMI 1 (KRISS, Rep. of Korea)
Calibration of NMI 2 (CSIR, South Africa)
Calibration of NMI 3 (CMS/ITRI, Rep. of China)
Calibration of NMI 4 (SPRING, Singapore)
Calibration of NMI 5 (NMIJ/AIST, Japan)
Calibration of NMI 6 (NMIA, Australia)
Calibration of NMI 7 (NML-SIRIM, Malaysia)
Calibration of NMI 8 (NIM, P.R. of China)
Draft A report
Draft B report
Start Date
1 Jun, 2005
1 Jul, 2005
1 Sep, 2005
1 Nov, 2005
1 Jan, 2006
1 Mar, 2006
1 May, 2006
1 Jul, 2006
1 Sep, 2006
1 Nov, 2006
1 Jan, 2007
1 Mar, 2007
1 May, 2007
1 July, 2007
End Date
30 Jun, 2005
31 Aug, 2005
31 Oct, 2005
31 Dec, 2005
28 Feb, 2006
30 Apr, 2006
30 Jun, 2006
31 Aug, 2006
31 Oct, 2006
31 Dec, 2006
28 Feb, 2007
30 Apr, 2007
30 Jun, 2007
31 Aug, 2007
However, the actual measurements were delayed from the above plan due to each of the
laboratory's specific circumstance, such as customs clearance, re-measurements, etc. Table 2-4-2
lists the actual time sequence.
Table 2-4-2. History of the comparison measurements.
Activity
KRISS,
NMISA,
CMS/ITRI,
NMC-A*STAR,
NMIJ/AIST,
NMIA,
NML-SIRIM,
NIM,
VNIIOFI
Pre-draft A process
NIM
KRISS,
1st measurements
2nd measurements
3rd measurements
4th measurements
5th measurements
6th measurements
7th measurements
8th measurements
9th measurements
Re-measurements
Final measurements
Occupied period
01 Jan. 2006 ~ 09 Mar.
18 Mar. 2006 ~ 19 Apr.
11 May 2006 ~ 28 Jun.
18 Jul. 2006 ~ 13 Sep.
06 Oct. 2006 ~ 23 Nov.
18 Dec. 2006 ~ 06 Mar.
28 Mar. 2007 ~ 21 Jun.
28 Jul. 2007 ~ 18 Oct.
01 May 2008 ~ 31 Oct.
20 Nov. 2008 ~ 30 Jan.
13 Nov. 2009 ~ 15 Apr.
20 May 2010 ~ 31 Jan.
2006
2006
2006
2006
2006
2007
2007
2007
2008
2009
2010
2011
All the comparison reports from original 8 participants arrived to KRISS by the end of July,
2008 while VNIIOFI conducted its measurements. Since VNIIOFI’s results were agreed to
append in the appendix section, the pre-draft A process began on 20 November, 2008 without
VNIIOFI by circulating the uncertainty budgets of all participants blinded and distributing the
8
APMP.PR-S2 Fiber Optic Power Responsivity
relative data of each participant to each of them. When participants were confirming their
relative data, NIM claimed its re-measurement because the correction factor change of the
artifact before and after NIM’s measurements was relatively larger compared to the other times.
The coordinator postponed the decision until checking the status of the artifact when VNIIOFI
returned it.
It took almost a year until the status of the artifact was checked because the artifact did not
return to KRISS for a while due to the internal problems of VNIIOFI’s administration and long
occupation by Russian customs office. Then, NIM’s re-measurement was decided when the
correction factor change of the artifact before and after VNIIOFI’s measurements was identified
to be much smaller than that of NIM’s.
After NIM’s re-measurements finished, the artifact returned to KRISS in May, 2010.
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APMP.PR-S2 Fiber Optic Power Responsivity
3. Description of the comparison artifact
The comparison artifact was a fiber optic power meter consisting of a control unit and an optical
head to collect radiant flux coming from the FC/PC type fiber optic connector end as shown in
Fig. 3-1 and 3-2. It was manufactured by ILX Lightwave, Inc. in 2005 with the model number
of FPM-8210 and the serial number of 82103878. KRISS purchased this product with its own
budget but later received reimbursement through APEC-TILT fund via APMP in 2005. It was
agreed that the artifact should be safely preserved in the pilot laboratory after completion of
comparison measurements for the future application. Acknowledgement to APMP and APECTILT
The optical head consisted of an InGaAs photodiode and a small integrating sphere that
enabled this power meter to be independent of the state of polarization from the fiber optic
connector end, which gave the reason to select it as the comparison artifact.
The optical head were connected to the control unit with an electrical cable. The control unit
had a display to indicate the radiant power level either in linear scale (W) or logarithmic scale
(dBm or dB) and wavelength in nm. A printed manual was included in the artifact package so
that participants could refer to it when they need to set wavelength, gain range, power unit,
GPIB address, and so on. Two FC/PC type fiber optic patch cords were also included in the
artifact package as described in Section 2.3.
FOPM Contoller/Display Unit
102.351
1310
Mains cable
plug
Optical head
FC receptacle
Electrical cable
Fiber optic patch cord
(FC/PC to FC/PC)
Fig. 3-1. A schematic of the comparison artifact.
10
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 3-2. Photographs of the artifact.
Fig. 3-3. Photographs of the artifact package.
11
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 3-3 shows the artifact package to transport from one country to another. The control unit
and the optical head were put into transparent plastic bags with desiccants (silica gel) and
securely tied with strings around the electrical cable, respectively. They were securely placed in
a polystyrene plate in a thick paper box and covered with another polystyrene plate. The two
fiber optic patch cords, the mains cable and the manual were placed on the cover plate, and then
the paper box was sealed with packing tape. Finally, the paper box was put into a wooden box
and all the necessary information sheets were attached to it.
Transportation fees were shared by all participants. KRISS paid the cost of shipment to each
participant and each participant paid the individual cost from customs clearance to shipment to
KRISS. The costs were partially reimbursed by APMP in 2006 only.
12
APMP.PR-S2 Fiber Optic Power Responsivity
4. Measurement Capability and Results of Pilot Laboratory
4.1. Traceability
The KRISS reference standard of the fiber optic power responsivity is an electrically calibrated
pyroelectric radiometer (ECPR). The ECPR is a thermal detector coated with a radiation
absorbing material that enables the detector to be spectrally insensitive over the wavelength
region from visible to mid-IR. The absorbed radiant power causes temperature change and the
radiant power is then substituted by the electrical power through pyroelectricity that causes the
same temperature change. The correction factor of the ECPR is calibrated using the radiant
power of a laser beam measured by the KRISS Si-trap detector at 633 nm in an underfill
condition. The responsivity of the KRISS Si-trap detector is calibrated using the KRISS
absolute cryogenic radiometer. The correction factor of the ECPR at 633 nm is then expanded to
near IR region using the spectral flatness of the ECPR. The correction factor of the KRISS
working standard or a fiber optic power meter (FOPM) can be calibrated at -10 dBm using the
radiant power of a laser diode delivered through a fiber optic patch cord measured by the ECPR
with an appropriate fiber optic receptacle attached to the ECPR. Together with the linearity of
the fiber optic power meter calibrated using a superposition method, the correction factor of the
fiber optic power meter can be calibrated in the range between -50 dBm and 5 dBm. Therefore,
the traceability of the fiber optic power responsivity measurements at KRISS is as shown in Fig.
4-1-1.
KRISS Absolute Cryogenic Radiometer
Si-trap dector
Electrically Calibrated Pyroelectric Radiometer
-10 dBm
KRISS Working Standard
Fiber Optic Power Meter
Fiber Optic Power Linearity
(Superposition method)
-50 ~ +5 dBm
Fiber Optic Power Meter
Fig. 4-1-1. Traceability of fiber optic power responsivity measurements at KRISS.
13
APMP.PR-S2 Fiber Optic Power Responsivity
4.2. Description of measurement facility
The KRISS fiber optic power responsivity measurement facility is as shown in Fig. 4-2-1.
Tunable laser sources made by external cavity laser diodes or DFB laser diodes were used as
optical sources. The optical beams from the sources were collimated out from the fiber optic
patch cords and in to another fiber optic patch cords using appropriate lenses to make 20 cmlong free space gap between them in order to move the chopper of the ECPR into the optical
beam when the ECPR measured the radiant power at the corresponding wavelength. Variable
optical attenuators (VOA’s) adjusted the radiant power levels to be -10 dBm at the final output
end. A broadband fiber optic coupler with a splitting ratio of 90:10 was used to tap 10 % of light
out of the optical path and fed into the multi-wavelength meter in order to measure the source
wavelengths. A motorized polarization controller was inserted optionally in case that the state of
polarization was required to be changed. Fiber optic isolators were used to reduce the radiant
power fluctuation caused by interferences due to reflections possibly occurring at the fiber optic
connector interfaces. In Fig. 4-2-1, the vertical line in the small rectangle indicates FC/PC to
FC/PC interface and the slanted line FC/APC to FC/APC interface.
MWM
TLS or DFB-LD
1310 nm
VOA
Broadband
Coupler
1310 nm
chopper
90/10 Coupler
1550 nm
TLS or DFB-LD
1550 nm
MPC
ECPR
FOI (1550 nm)
Comparison
Artifact
FOI (1310 nm)
Fig. 4-2-1. Schematic diagram of the KRISS fiber optic power measurement facility. DFB-LD,
distributed feedback laser diode; ECPR, electrically calibrated pyroelectric radiometer; MPC,
motorized polarization controller; MWM, multi-wavelength meter; FOI, fiber optic isolator;
TLS, tunable laser source; VOA, variable optical attenuator.
Fig. 4-2-1 can be regarded as a snap shot when the fiber optic power was being measured
14
APMP.PR-S2 Fiber Optic Power Responsivity
with the ECPR at 1550 nm. After the ECPR measurement, the chopper moved out of 1550 nm
beam path and the fiber output end was connected to the FOPM that was a comparison artifact,
after the position of the FOPM head was shifted to where the ECPR had been. Then, the radiant
power was measured with the FOPM. The correction factor of the FOPM at the radiant power
level of about 0.1 mW (-10 dBm) was then determined by the ratio of measured value with the
ECPR to that of the FOPM and the correction factor of the ECPR as in Eq. (4-2-1),
P
k f  ke   ke  e
P
 f




,
(4-2-1)
where kf, ke, , Pe, and Pf are the correction factor of FOPM, the correction factor of ECPR,
power ratio, measured value with ECPR, and measured value with FOPM, respectively.
For 1310 nm, the measurement procedure was the same but the fiber optic isolator for 1550
nm was replaced by that of 1310 nm.
Fig. 4-2-2 shows the fiber optic power linearity measurement facility using a superposition
method. The laser from a DFB laser diode was split into two paths by a broadband fiber optic
coupler. The VOA in each path could shut the laser or change the attenuation level precisely.
The two laser beams after the VOA’s were then combined into a fiber with another broadband
fiber optic coupler and delivered to the fiber optic power meter. In order to remove interference
effect between the two laser beams when combining, a single mode optical fiber with a length
of about 20 km was inserted in one of the two paths since the line width of the DFB laser diode
was known to be a few MHz.
VOA-1
Broadband
Coupler
DFB-LD
50/50
Broadband
Coupler
SMF 20 km
50/50
VOA-2
1310 nm
1550 nm
Detector
Head
Comparison
Artifact
Fig. 4-2-2. Schematic diagram of the KRISS fiber optic power linearity measurement facility
using superposition method. DFB-LD, distributed feedback laser diode; SMF, single mode fiber;
VOA, variable optical attenuator.
Using this facility, a partial nonlinearity factor f defined by Eq. (4-2-2) could be measured,
15
APMP.PR-S2 Fiber Optic Power Responsivity
where R is the responsivity of the artifact. D1 is the measured power when only VOA-1 is open.
Likewise D2 is the measured power when only VOA-2 is open with D1 D2. Then D3 is the
measured power when both VOA-1 and VOA-2 are open. The partial nonlinearity factor f can
be measured every 3 dB step by changing the attenuators such that D3 can become equal to D1
in the previous step. The total nonlinearity factor F can then be calculated according to Eq. (4-23) and the correction factor at a certain level, e.g. -30 dBm, can be determined using the
correction factor at -10 dBm (reference level) and the total nonlinearity factor F according to Eq.
(4-2-4). If the level is not exactly the same as (-10–3j) dBm (j=0, 1, 2,), the correction factor
can be assumed to be equal to that of the nearest neighboring level unless the gain range is
changed.
f ( 2 1 P) 
D3
R( P)
R( P) P


1
1
1
1
1
R(2 P) R(2 P)2 P  R(2 P)2 P D1  D2
F ( P  2 n Pr ) 
n
 f (2
k
Pr ) 
k 1
R( Pr ) k f ( P )

R ( P ) k f ( Pr )
 k f ( P)  k f ( Pr ) F ( P )
(4-2-2)
(4-2-3)
(4-2-4)
4.3. Laboratory conditions
The laboratory temperature was controlled to be (23  2) C and the humidity (45  15) %
throughout the calibration and measurements.
4.4. Measurement procedure
Before measurements, all the equipments were turned on and they were left to get stabilized at
least for one hour.
The detailed procedure for the calibration of the fiber optic power responsivity at -10 dBm is
as follows:
(1) Configure the calibration setup as shown in Fig. 4-2-1 to operate at 1310 nm.
(2) Adjust the height of the detector heads of the ECPR and the artifact to be the same.
(3) Set the wavelength of the artifact to 1310 nm.
(4) Adjust the zero point of the ECPR and the artifact.
(5) Slide the beam chopper of the ECPR to the collimated optical beam.
(6) Connect the fiber end to the detector head of the ECPR.
16
APMP.PR-S2 Fiber Optic Power Responsivity
(7) Set the radiant power to be -10 dBm (0.1 mW) using the variable optical attenuator.
(8) Measure the radiant power with the ECPR.
(9) Disconnect the fiber end from the ECPR.
(10) Slide the beam chopper out from the collimated optical beam.
(11) Connect the fiber end to the detector head of the artifact.
(12) Measure the radiant power with the artifact.
(13) Repeat the step from (5) to (12) at least four times more.
(14) If the measurement is finished at 1310 nm, change the source to 1550 nm and conduct
the step (3) to (13), where 1310 nm is replaced by 1550 nm.
The detailed procedure for the calibration of the fiber optic power responsivity at -20 dBm
and -30 dBm is as follows:
(1) Configure the calibration setup as shown in Fig. 4-2-2 to operate at 1310 nm.
(2) Set the wavelength of the artifact to 1310 nm.
(3) Adjust the zero point of the artifact.
(4) Open VOA-1 and adjust the attenuation level so that the artifact can indicate -13 dBm
while VOA-2 is closed.
(5) Open VOA-2 and adjust the attenuation level so that the artfact can indicate the same
-13 dBm while VOA-1 is closed.
(6) Record the radiant power with VOA-1 open and VOA-2 closed.
(7) Record the radiant power with VOA-1 closed and VOA-2 open.
(8) Record the radiant power with both VOA-1 and VOA-2 open.
(9) Increase the attenuation level of VOA-1 and VOA-2 by 3 dB.
(10) Repeat the step from (6) to (7) until the radiant power with either VOA open becomes
less than -30 dBm.
(11) Repeat the step from (4) to (10) at least four times more.
(12) If the measurement is finished at 1310 nm, change the source to 1550 nm and conduct
the step (2) to (11), where 1310 nm is replaced by 1550 nm.
4.5. Measurement results
Table 4-5-1 summarized the measurement results using KRISS’ own fiber connector that was
the fiber connector of the fiber optic isolator in Fig. 4-2-1 and the common fiber connector
labeled as FC-1.
17
APMP.PR-S2 Fiber Optic Power Responsivity
Table 4-5-1. Correction factor of the comparison artifact measured at KRISS.
Wavelength
(nm)
Power level
(dBm)
Fiber
connector
Correction
factor
Uncertainty
(Type A)
1310
1310
1310
1310
1310
1310
1550
1550
1550
1550
1550
1550
-10
-10
-20
-20
-30
-30
-10
-10
-20
-20
-30
-30
KRISS
FC-1
KRISS
FC-1
KRISS
FC-1
KRISS
FC-1
KRISS
FC-2
KRISS
FC-3
1.01413
1.01164
1.01292
1.01043
1.01443
1.01193
0.99736
0.99484
0.99574
0.99323
0.99701
0.99450
0.00015
0.00012
0.00008
0.00008
0.00012
0.00012
0.00018
0.00022
0.00004
0.00004
0.00011
0.00011
Relative
uncertainty
(Type A) (%)
0.015
0.012
0.008
0.008
0.012
0.012
0.018
0.022
0.004
0.004
0.011
0.011
The relative deviation of correction factors in case of FC-1 from that of KRISS’ own fiber
connector at -10 dBm level was -0.246 % at 1310 nm and -0.252 % at 1550 nm. Note that these
values were the same at different radiant power levels since we determined the correction
factors at different levels through nonlinearity measurements, not through comparison with
reference.
The above measurements of KRISS were conducted using auto range function of the artifact
and the range was always 4 (1 A) for -10 dBm, 5 (100 nA) for -20 dBm, and 6 (10 nA) for
-30 dBm regardless of wavelength.
4.6. Uncertainty
From Eq. (4-2-1), we can derive the uncertainty propagation equation as shown in Eq. (4-6-1)
since the correction factor of ECPR ke is uncorrelated with the radiant power ratio .
2
ur2 (k f
2
2
 u (k f ) 
 u (ke )   u (  ) 
2
2
)
 
 
  ur (ke )  ur (  )
k
k


 e  
 f 
(4-6-1)
The uncertainty of the correction factor of ECPR at the calibration wavelength (633 nm),
spectral dependence of ECPR, and the uncertainty caused by chopper alignment were major
sources of the uncertainty for the correction factor of ECPR when using it near IR region.
The sources of uncertainty for the radiant power ratio were repeatability, temporal stability of
optical source including the optical circuits, resolution of ECPR and the artifact, wavelength
mismatch between the optical source and set wavelength of the artifact, and temperature
18
APMP.PR-S2 Fiber Optic Power Responsivity
dependence of the artifact.
The uncertainty budgets of KRISS are as shown in Table 4-6-1 and Table 4-6-2 in case of
using the common fiber connector, FC-1. In case of using KRISS’ own fiber connector, only the
repeatability component is slightly different.
Table 4-6-1. Uncertainty budget of correction factor at 1310 nm.
1310 nm, -10 dBm
Source of uncertainty
Relative
standard
uncertainty
Probability
distribution
Sensivity
coefficient
Correction factor of reference standard
Correction factor at cal. wavelength
0.200 %
normal
Spectral dependence
0.191 %
rectangular
Alignment
0.0577 %
rectangular
Ratio of ref.std. to artifact
Repeatability
0.0120 %
t
Source stability
0.0195 %
rectangular
Resolution
Resolution of ref.std
0.0288 %
rectangular
Resolution of artifact
0.00285 %
rectangular
Wavelength mismatch
0.0303 %
t
Temperature dependence of artifact
0.231 %
rectangular
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
Relative
Standard
uncertainty
Degree
of
freedom
1
1
1
0.200 %
0.191 %
0.0577 %



1
1
0.0120 %
0.0195 %


1
1
1
1
%
%
%
%
%
%


1.3E+06

3.5E+06
Relative
Standard
uncertainty
0.368 %
Degree
of
freedom

0.00803
0.0693
0.374
0.75
%
%
%
%


2.4E+07
Relative
Standard
uncertainty
0.368 %
Degree
of
freedom

0.0288
0.00285
0.0303
0.231
0.368
0.74
1310 nm, -20 dBm
Source of uncertainty
Relative
standard
uncertainty
0.368 %
Probability
distribution
Sensivity
coefficient
Correction factor at -10 dBm
normal
1
Nonlinearity
Repeatability
0.00803 %
t
1
Nonlinearity factor
0.0693 %
rectangular
1
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
1310 nm, -30 dBm
Source of uncertainty
Relative
standard
uncertainty
0.368 %
Probability
distribution
Sensivity
coefficient
Correction factor at -10 dBm
normal
1
Nonlinearity
Repeatability
0.0115 %
t
1
Nonlinearity factor
0.0167 %
rectangular
1
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
19
0.0115
0.0167
0.368
0.74
%
%
%
%


5.3E+06
APMP.PR-S2 Fiber Optic Power Responsivity
Table 4-6-2. Uncertainty budget of correction factor at 1550 nm.
1550 nm, -10 dBm
Source of uncertainty
Relative
standard
uncertainty
Probability
distribution
Sensivity
coefficient
Correction factor of reference standard
Correction factor at cal. wavelength
0.200 %
normal
Spectral dependence
0.191 %
rectangular
Alignment
0.0577 %
rectangular
Ratio of ref.std. to artifact
Repeatability
0.0225 %
t
Source stability
0.0415 %
rectangular
Resolution
Resolution of ref.std
0.0288 %
rectangular
Resolution of artifact
0.00280 %
rectangular
Wavelength mismatch
0.123 %
t
Temperature dependence of artifact
0.231 %
rectangular
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
Relative
Standard
uncertainty
Degree
of
freedom
1
1
1
0.200 %
0.191 %
0.0577 %



1
1
0.0225 %
0.0415 %


1
1
1
1
%
%
%
%
%
%


6.0E+06

3.6E+05
Relative
Standard
uncertainty
0.389 %
Degree
of
freedom

0.00386
0.0938
0.400
0.80
%
%
%
%


4.6E+08
Relative
Standard
uncertainty
0.389 %
Degree
of
freedom

0.0288
0.00280
0.123
0.231
0.389
0.78
1550 nm, -20 dBm
Source of uncertainty
Relative
standard
uncertainty
0.389 %
Probability
distribution
Sensivity
coefficient
Correction factor at -10 dBm
normal
1
Nonlinearity
Repeatability
0.00386 %
t
1
Nonlinearity factor
0.0938 %
rectangular
1
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
1550 nm, -30 dBm
Source of uncertainty
Relative
standard
uncertainty
0.389 %
Probability
distribution
Sensivity
coefficient
Correction factor at -10 dBm
normal
1
Nonlinearity
Repeatability
0.0107 %
t
1
Nonlinearity factor
0.0202 %
rectangular
1
Relative Combined Uncertainty
Relative Expanded Uncertainty (Coverage factor, k = 2; Level of confidence, approx. 95 %)
20
0.0107
0.0202
0.389
0.78
%
%
%
%


7.0E+06
APMP.PR-S2 Fiber Optic Power Responsivity
5. Measurement Capabilities and Results of Participants
5.1. NMISA
5.1.1. Introduction
This report contains NMISA’s results for comparison APMP.PR-S2 of Fibre Optic Power
Responsivity. The measurements at NMISA were performed over the period 13 to 20 April 2006.
5.1.2. Reference Standards, Equipment and Experimental Set-up & Method
The primary reference used for the comparison measurements was a room temperature absolute
radiometer. Literature reference [1] contains some details about the absolute radiometer, and
Chapter 6 of literature reference [2] contains details on the theory and determination of
instrumental corrections particular to it.
For fibre optic purposes the absolute radiometer is fitted with an insert with a fibre optic port,
which reaches to within close proximity of the sensor cavity of the absolute radiometer. This
enables feeding of radiant power via optical fibre, directly to the absolute radiometer, for
absolute measurement. Therefore a fibre optic power meter requiring calibration can be
calibrated by comparison to the absolute radiometer by moving the fibre between them.
This is the approach that was used to calibrate the comparison transfer detector (comparison
artifact). Fig. 5-1-1 shows the measurement set-up (photograph) and Fig. 5-1-2 is a simple
diagrammatic representation of the set-up and measurement process.
The optical sources were FP lasers, for which the wavelength can be optimised by adjusting its
power. For the 1550 nm FP laser a centre wavelength within 0.1 nm of nominal could be
achieved. For the 1310 nm FP laser the closest centre wavelength that could be achieved was
≈1307 nm.
The laser radiation was fed to the detectors via a variable optical attenuator, which served
both to set the desired power level to the detectors, and to limit back-reflections to the laser.
5.1.3. Results
The results are expressed as a correction factor, as defined by the protocol, i.e. the “ratio of the
optical power determined by the participating laboratory to the reading displayed by the artifact
(Watt per reading in Watt)”. The results are given in Table 5-1-1. Uncertainty budget details are
given in Table 5-1-2 to Table 5-1-5, and further discussion about the contributors in §5.1.4.
The results are for powers 0.1 mW and 0.01 mW. No result is reported for power 0.001 mW.
21
APMP.PR-S2 Fiber Optic Power Responsivity
The reason is that the measurements at 0.1 mW and 0.01 mW were done directly against our
primary reference (absolute radiometer), BUT measurements for 0.001 mW not. Measurements
for 0.001 mW were done via a linearity measurement approach but were found to be unsuitable
for determining the correction factor at this power level.
The actual centre wavelengths of the FP sources were calculated from spectral traces taken
with an optical spectrum analyzer.
Fig. 5-1-1. Photograph of measurement set-up for calibration of comparison artifact: (1)
Absolute radiometer optical head. (2) Absolute radiometer preamplifier and bridge unit. (3)
Absolute radiometer control unit. (4). ILX Lightwave FPM-8210 optical head. (5) ILX
Lightwave FPM-8210 readout unit. (6) Mainframe unit containing FP laser source module and
variable optical attenuator. The other three instruments at the top of the photograph are digital
multimeters used with the absolute radiometer for measurement and monitoring.
22
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-1-2. Measurement set-up and comparison of unit under calibration with absolute
radiometer.
5.1.4. Uncertainties
The detailed uncertainty budgets are given in Table 5-1-2 to Table 5-1-5.
The following potential contributions were considered negligible or not relevant:
Uncertainties:
· Linearity of reference detector: Because the reference detector works on the electrical
substitution principle non-linearity is negligible.
· Drift of reference detector: This is implicitly contained in the ESDM.
· Connector tightening effects: Owing to the design of the optical port on both our reference
detector and the comparison artifact, tightening effects is negligible. The tip of the fibre is
open, unconstrained.
· Linearity of comparison artifact: Not relevant because the reported results apply to a specific
radiant power level.
· Optical fibre connector effects / Inter-reflection (detector / connector). The nature of the
comparison artifact’s optical head, i.e. a sphere, causes such effects to be negligible.
The following is explains the basis of the uncertainty contributions in the uncertainty budgets:
· Uncertainty contributions associated with the reference detector (absolute radiometer). Lead
heating effect, Substitution non-equivalence correction, Reflection correction, Uncertainty of
spatial uniformity correction: The corrections had been empirically measured and the
uncertainties associated with the corrections.
23
APMP.PR-S2 Fiber Optic Power Responsivity
· Uncertainty contributions associated with the reference detector (absolute radiometer).
Electrical power measurement: Uncertainty derived from electrical measurands.
· Uncertainty contributions associated with the reference detector (absolute radiometer).
Resolution: Its resolution is 0.001 uW, which translates to relative resolutions of 0.001% and
0.01% at measured radiant powers of 0.1 mW and 0.01 mW respectively.
· Fibre flexing (in-fibre back-reflection/polarisation / laser feedback effects / Coherence
effects): Based on a set of fibre flexing measurements by keeping the fibre connected to a
photodiode and performing movements that flexes the fibre in a way equivalent to that during
actual calibration measurements.
· Effect of wavelength offset, wavelength uncertainty & detector relative spectral responsivity.
Our reference detector has a flat response, but the comparison artifact not. The “Input
quantity” in the uncertainty budget was derived as
(offset) 2  ( wavelength uncertainty) 2 and the sensitivity coefficients at 1310 nm and 1550
nm was derived from the sample responsivity plot available in the instrument manual on page
22.
· Temperature sensitivity of UUT responsivity. The worst case deviation from the 23°C
environmental condition required by the protocol was 1.2°C and the temperature
measurement uncertainty was 0.4°C, which can be combined as
(1.2) 2  (0.4) 2 C  1.27 C The sensitivity coefficient was taken as the manufacturer
specification for temperature coefficient, 0.2 %/°C.
· ESDM of the readings: The ESDM was calculated from measurement data.
24
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-1-1. Results of comparison artifact calibration.
Table 5-1-2. Uncertainty budget for correction factor: Source wavelength 1310 nm, instrument
range setting 4, instrument wavelength setting 1310.0 nm. The input quantities are all
uncorrelated.
25
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-1-3. Uncertainty budget for correction factor: Source wavelength 1310 nm, instrument
range setting 5, instrument wavelength setting 1310.0 nm. The input quantities are all
uncorrelated.
Table 5-1-4. Uncertainty budget for correction factor: Source wavelength 1550 nm, instrument
range setting 4, instrument wavelength setting 1550.0 nm. The input quantities are all
uncorrelated.
26
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-1-5. Uncertainty budget for correction factor: Source wavelength 1550 nm, instrument
range setting 5, instrument wavelength setting 1550.0 nm. The input quantities are all
uncorrelated.
5.1.5. Literature References
[1] F. Hengstberger, R.E. Dressler, L.A.G. Monard, C.J. Kok, and R. Turner, “Further advances
with the fully automated absolute radiometer developed at the NPRL”, Proc. of an
International Meeting on Advances in Absolute Radiometry (1985), Cambridge,
Massachusetts, P.V. Foukal, ed., Atmospheric and Environmental Research Inc., Cambridge,
Mass., pp.34-37.
[2] F. Hengstberger, ed, Absolute Radiometry – Electrically calibrated detectors of optical
radiation, Academic Press (1989).
27
APMP.PR-S2 Fiber Optic Power Responsivity
5.2. CMS/ITRI
5.2.1. Description of the measurement facility and traceability in CMS/ITRI
Fig. 5-2-1 illustrates the measurement system configuration of optical fiber power measurement.
The system consists of laser source, fiber isolator, fiber attenuator (Anritsu ), 12 fiber coupler,
and monitor detector. All fibers of system are single-mode. The fiber pigtailed laser diode
(Thorlabs/LPS-SMF28-1310-FC) and DFB laser diode (NEL/NLK1556STG-BX) are used as
standard laser sources. The wavelengths of sources are adjusted to 1310.46 nm and 1550.01 nm
by wavemeter (Berleigh/WA-1550). The monitor detector is used to observe the stability of light
source and the attenuator controls the power level. The output power of KC fiber is measured by
absolute radiometer, and then measured by the artifact. Fig. 5-2-2 shows the traceability of
optical fiber power measurements.
Micro-current
meter
Fiber
12
fiber
coupler
Monitor
Detector
pigtailed
Fiber
Temperature
isolator
controller
Fiber
attenuator
KC Fiber
Absolute
Fiber
adaptor
radiometer
Laser
diode/DFB laser diode
Laser
driver
Fiber
adaptor
artifact
Fig. 5-2-1. Optical fiber power meter measurement system configuration.
28
diode
APMP.PR-S2 Fiber Optic Power Responsivity
Room temperature
absolute radiometer
artifact
Fig. 5-2-2. Traceability.
5.2.2. Calibration results
The calibration results for 1310 nm and 1550 nm are shown in the following tables. The
ambient temperature and relative humidity are (23.0  1.5) C and (45  10) %, respectively.
Table 5-2-1. Calibration results for 1310 nm.
Gain range
Calibration factor
(W/reading in W)
Relative
expanded
uncertainty (%)
(k=1.97)
1310
auto
1.027
1.4
FC-1
1310
auto
1.025
1.4
1.005-1.08
FC-1
1310
auto
1.020
1.4
110-120
CMS/ITRI
1310
auto
1.029
1.4
Fiber used
Wavelength
setting
(nm)
107-120
FC-1
10.3-10.9
Meter power
range (W)
Table 5-2-2. Uncertainty budget for 1310 nm.
Source
Type
Relative standard uncertainty
(%)
Degree of freedom 
Repeatability
A
0.26
12
Laser power drift
B
0.38
200
0.50

0.10
200
0.69
eff =466
1.4
k=1.97
Room temperature
B
absolute radiometer
Artifact spectral
B
responsivity
Relative combined
standard uncertainty
Relative expanded uncertainty
29
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-2-3. Calibration results for 1550 nm.
Gain range
Calibration factor
(W/reading in W)
Relative
expanded
uncertainty (%)
(k=1.96)
1550
auto
1.014
1.2
FC-1
1550
auto
1.010
1.2
1.1-1.2
FC-1
1550
auto
1.006
1.2
115-130
CMS/ITRI
1550
auto
1.019
1.2
Fiber used
Wavelength
setting
(nm)
105-120
FC-1
10.8-11.5
Meter power
range (W)
Table 5-2-4. Uncertainty budget for 1550 nm.
Source
Type
Relative standard
uncertainty (%)
Degree of freedom 
Repeatability
A
0.12
12
Laser power drift
B
0.25
200
0.50

0.10
200
0.58
eff = 3032
1.2
k=1.96
Room temperature
B
absolute radiometer
Artifact spectral
B
responsivity
Relative combined
standard uncertainty
Relative expanded uncertainty
30
APMP.PR-S2 Fiber Optic Power Responsivity
5.3. NMC-A*STAR
NMC-A*STAR is a new name of national metrology institute of Singapore. It was SPRING at
the time of the measurement and reporting. Therefore, the following measurement report
contains the name SPRING.
5.3.1. Measurement facility
The measurement was carried out by using following reference standard, intensity stabilized
tunable laser sources, variable attenuator and other equipment in SPRING Singapore:
a) Laboratory reference standard: InGaAs photodiode (s/n: InGaAs-05) (900-1640nm)
calibrated on 5 July 2006.
b) Tunable laser sources: ANDO AQ4321 tunable laser source (s/n: 10158008) (1520 nm to
1620nm) and Santec ECL-210 tunable laser source (s/n: 6010002) (1270nm to 1350nm).
c) Variable attenuator: EXFO IQ-3100 variable attenuator (s/n:118320-35)
d) Dual stage isolators: COPENETI isolators (p/n:IS-D-13/15-P-L-10-FC)
e) Current-to-voltage converter: Vinculum E755 I-V converter (s/n:OP002) calibrated on 3
April 2006.
f) Digital multimeter: Keithley 2000 DVM (s/n: 0687186) calibrated on 28 March 2006.
5.3.2. Measuring technique
The artifact (the fiber optic power meter, FOPM, provided by the pilot lab) was calibrated by a
SPRING’s reference standard, an InGaAs photodiode (RS-PD), under intensity-stabilized laser
beams from tunable laser sources at wavelengths of 1310 nm and 1550 nm.
The detector of the FOPM and the RS-PD were connected through either the fiber patch cord
provided by the pilot lab or the fiber isolator of SPRING Singapore to the tunable laser source
alternatively. The laser power level of -10 dBm, -20 dBm and -30 dBm were obtained from laser
sources through a variable attenuator. The short-circuit photocurrents from InGaAs photodiode
was measured using calibrated current-to-voltage converter and digital multimeter. The
correction factor [CF()] defined as the ratio of the optical power determined by SPRING
Singapore [PSPRING()] to the reading displayed by the artifact [PArtifact()] was calculated by Eq.
(5-3-1).
CF ( ) 
PSPRING ( )
PArtifact ( )
31
(5-3-1)
APMP.PR-S2 Fiber Optic Power Responsivity
As the wavelength accuracy of both laser sources is better than 0.1nm, no correction was made
to the measurement results for the central wavelength offsets. A schematic diagram of the
measurement setup is shown in Fig. 5-3-1 as follow.
Fig. 5-3-1. Schematic diagram of measurement setup in SPRING Singapore.
5.3.3. Traceability and uncertainty budget
The traceability of SPRING’s fibre optic power measurement is based on our spectral
responsivity scale as shown in Fig. 5-3-2.
The laser wavelength measurement is traceable to the primary standard of laser wavelength
maintained in SPRING Singapore.
The electrical measurement is traceable to the primary standards of current and voltage
maintained in SPRING Singapore.
The breakdown uncertainty budget of measurement was estimated and its results are shown in
the Table 5-3-2 ~ 5-3-5.
32
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-3-2. Traceability chart for APMP.PR-S2 comparison (All uncertainty values in
the chart refer to combined standard uncertainty, k=1).
5.3.4. Laboratory Conditions
Temperature: (23±2) C and Relative Humidity: (60±10) %.
5.3.5. Measurement Results
The measurement results of SPRING Singapore was summarized in Table 5-3-1.
33
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-3-1. Calibration result of SPRING Singapore.
5.3.6. Uncertainty budgets
Table 5-3-2 and 5-3-3 shows the uncertainty budget when the FC/PC output end of SPRING’s
fibre isolator was used, whereas Table 5-3-4 and Table 5-3-5 shows the uncertainty budget when
the FC-1 was used.
34
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-3-2. Uncertainty budget for measurement at 1310nm by using SPRING’s FC/PC fibre
isolator.
35
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-3-3. Uncertainty budget for measurement at 1550nm by using SPRING’s FC/PC fibre
isolator.
36
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-3-4. Uncertainty budget for measurement at 1310nm by using given FC/PC patch cord
(s/n:FC-1).
37
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-3-5. Uncertainty budget for measurement at 1550nm by using given FC/PC patch cord
(s/n:FC-1).
38
APMP.PR-S2 Fiber Optic Power Responsivity
5.4. NMIJ/AIST
5.4.1. NMIJ Working Standard for Optical Fiber Power: Optical Fiber Power
Calorimeter
As schematically illustrated in Fig. 5-4-1, the NMIJ working standard for optical fiber power,
optical fiber power calorimeter, consists of the main body and a detachable adaptor for optical
fiber power input. The structure of the main body is similar to the Japan’s national standard of
open beam laser power [1]. We measure optical power with the calorimeter by electrothermal
substitution technique under isothermal temperature control. The advantage of the
electrothermal substitution is that we can translate input optical power into electrical power
output, which is traceable to much more precise standards of electricity. Isothermal temperature
control of the optical absorber with heater and Pertier element enables us to eliminate the
fluctuation driven by convectional or radiation loss of heat on the optical absorber since the
temperature of the optical absorber is kept same with the ambient temperature, therefore
measurement uncertainty would be more reduced than the system without isothermal
temperature control. This type of calorimeter is equipped with NiP ultra-black absorber [2]; its
reflectance is less than 0.2 %. The calorimeter also has the compensative absorber [3] to
eliminate the effect from ambient temperature and/or atmospheric pressure fluctuation, so that
optical fiber power of less than 100 microwatt level can be determined with high accuracy.
The adaptor for optical fiber power input is attached in front of the NiP absorber, which
enables us to introduce the divergent beam from optical fiber.
The sensitivity of the calorimeter to optical power is determined using collimated beam by
comparison with the calorimeter so called H-3, which is Japan’s national standard for open
beam laser power. When the calorimeter is used as a standard for calibration of detectors under
test (DUT, c.f. optical power meters) for optical fiber power, we use the calibration
measurement system as shown in Fig. 5-4-2. To reduce the effect of light source (LD)
fluctuation, the optical fiber power is splitted and the power in one branch is monitored by
photodetector such as Ge or InGaAs photodiode. Using the optical fiber power calorimeter, we
can calibrate DUT directly without any transfer standards such as semiconductor photodiodes,
between national standard of optical power and DUT, therefore the calibration uncertainty can
be reduced.
There are several uncertainty factors in the calibration measurement of DUT using the optical
fiber power calorimeter as mentioned in the following section.
39
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-4-1: The schematic illustration of the optical fiber calorimeter: (a) structure of main body,
(b) detailed structure of absorber unit and block diagram of measurement system.
Fig. 5-4-2: The schematic diagram of the system for calibration of DUT with the optical fiber
power.
5.4.2. Uncertainty Analysis
Calibration measurement uncertainty using the NMIJ optical fiber power calorimeter was
evaluated for 100 uW, 1310/1550 nm. The uncertainties were evaluated in accordance with
international document standards [4]. The results are described in Table 5-4-1 ~ 5-4-4.
First, the calorimeter was calibrated with open beam of 1550 nm from laser diode at 1 mW
using the laser power national standard, therefore there are sensitivity calibration uncertainties,
including the uncertainty of the national standard and standard deviation of the measurement for
the calibration; 0.068%.
To measure the fiber optical power at 100 uW with the calibrated fiber calorimeter, the
uncertainty arises for non-linearity of the calorimeter between 1 mW and 100 uW. The
40
APMP.PR-S2 Fiber Optic Power Responsivity
nonlinearity was measured using small heater buried at the center of NiP absorber of the
calorimeter, applying known power to the heater. The uncertainty to determine the non-linearity
was 0.070 %.
When measuring the power of 1310 nm and so on in wavelength, the wavelength dependence
of NiP absorber affects the measurements. In manufacturer specification [2], the reflectance of
NiP absorber is ranging between 0.1 – 0.2 % for near infra-red region. The uncertainty due to
the reflectance fluctuation is calculated into 0.029 % assuming rectangular distribution.
Beam incident position also causes another uncertainty because of the non-uniformity of NiP
absorber. Detachable adapter would be exchanged periodically (typically once a year) for
sensitivity calibration with open beam using laser power national standard H-3, therefore the
position of beam center from optical fiber on NiP absorber may be fluctuated. The uniformity of
sensitive area of the absorber was examined by measuring open beam power with scanning 0.5
mm x 0.5 mm area on the absorber. The result was translated into the uncertainty of 0.067 %.
These uncertainties mentioned above are common to the uncertainty of open beam laser
power calorimeter. There are other uncertainty factors unique for the measurement of fiber
optical power, because of the divergent nature of its beam.
One is the divergent incidence on the NiP absorber. Sensitivity calibration of the calorimeter
is performed with collimated beam; therefore, divergent incidence from optical fiber to the
absorber would cause uncertainty since the reflectance of NiP would vary with incident angle of
optical power. Relation between reflectance of NiP and incident angle of optical power was
measured using the setup shown in Fig. 5-4-3 (boxed). Collimated beam was introduced into
integrating sphere, equipped with NiP absorber at the center of the sphere. Rotating the direction
of NiP absorber surface, we measure the optical power reflected by the NiP with InGaAs
photodiode. The results were shown in Fig. 5-4-3; Reflectance was normalized by the value at 0
degree (normal incidence). The reflectance goes up to 1.7 with 30 degree incidence. However,
according to the measurement of beam pattern emitted from optical fiber end, as shown in Fig.
5-4-4, optical power of more than 99.99% is within +/- 10 degree direction from normal
incidence, therefore the difference of the reflectance is only about 10 % between beam center
and edge. Since the reflectance itself is quite small (0.1 - 0.2 %), the uncertainty driven by the
angular incident of optical power is less than 0.01%.
Another factor is multi-reflection between NiP absorber and the inner wall of the fiber
adaptor, which also arises from the divergent incidence. If the NiP absorber shows completely
diffusive reflection, the multi-reflection is negligible. However, actual NiP absorber reflects a
part of incident optical power to the specular direction rather than diffusively. That causes
41
APMP.PR-S2 Fiber Optic Power Responsivity
another uncertainty for the fiber optical power measurements. The uncertainty calculated with
the beam pattern as shown in Fig. 5-4-4 was 0.139 %. The correction factor is -0.122 %.
The uncertainty due to DC voltage meter used to measure the heater power in electrical
substitution technique was 0.023 % according to the specification of manufacturer.
The optical fiber power calorimeter is operated in isothermal temperature control with
proportional feedback; therefore there is deviation due to the control. The uncertainty from the
control was found to be 0.014 % by the experiment.
Uncertainty due to temperature or wavelength dependence of the APMP artifact was
determined using data about ambient temperature obtained with a calibrated thermometer and
center wavelength of LD source measured with a calibrated spectrum analyzer during the
comparison measurements (See table 5-4-5 – 5-4-7).
Combining all of the uncertainty mentioned above and standard deviation of comparison
measurements (0.014 ~ 0.017 %, n=15), the expanded uncertainty for the calibration
measurement of the APMP artifact for 100 uW, 1310/1550 nm with APMP or NMIJ patch cord
using the optical fiber power calorimeter was 0.49 ~ 0.52 % (k=2).
Fig. 5-4-3: Relation between relative reflectance of NiP absorber and incident angle of optical
power. The reflectance at normal incident (0 degree) is normalized to be unity. Boxed:
schematic setup for the measurement.
42
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-4-4: Beam profile of divergent optical power emitted from optical fiber end. Boxed:
schematic setup for the measurement.
5.4.3. Low Fiber-Optic-Power (1, 10 W) Calibration With Optical Attenuation
Standard By Incremental Attenuation Method
Linearity of fiber-optic power meters is usually calibrated by the superposition method [5],
where desired attenuations are realized by summing up many 3 dB attenuation steps. For cases
where a gradual variation of linearity over a wide range is concerned, it is more convenient to
use the attenuation steps larger than 3 dB ones. Therefore we used incremental attenuation
method based on 10 dB steps. In this method a narrow range of calibrated linear response of a
reference power meter is sufficient to perform the wide dynamic range calibration of a test
meter.
The measurement setup is illustrated in Fig.5-4-5. The tunable LD source operates in the
1550/1310 nm band. Two attenuators, Att.1 and Att.2, are used; Att.1 is for level shift and Att.2
for step attenuation. The output port of Att.2 is connected to one end of a fiber optical patch
cord. The other end of the fiber is switched onto a reference meter (STD), or a test power meter
(DUT = APMP artifact in the comparison measurement), as in the following steps. Firstly, it is
connected to STD. The nominal 0 dB to 10 dB attenuation step of Att.2 is then calibrated
(ACAL(1)) at power level PCAL with STD, whose linearity has been calibrated beforehand by the
superposition method over a power range just wide enough to perform this calibration. Secondly,
the fiber end is connected to DUT. DUT’s uncorrected readings, AD(k), for the same nominal
43
APMP.PR-S2 Fiber Optic Power Responsivity
steps are recorded at a series of power levels, P(k), each level shifted from its previous level by
the same amount (in dB) as the step attenuation, A(k), at P(k). Thirdly, the fiber end is switched
back to STD and the attenuation step is calibrated again (ACAL(2)). Steps 1 to 3 are repeated to
evaluate experimental deviations. The relationship among AD(k), A(k), and P(k) are illustrated in
Fig.5-4-6. The nonlinearity of DUT, NL(n) (in dB), at power P(n) (in dBm) is given as:
(5-4-1)
Here, ADC(k)'s are hypothetical attenuation step readings with DUT and are calculated from
recorded readings AD(k)'s by:
(5-4-2)
where -SDPLΔPL2 corrects for the effect that the 0 dB to 10 dB switching of Att.2 changes the
polarization state of its output light by ΔPL2, which then affects the reading of DUT (AD(k))
through its sensitivity to polarization SDPL. Similarly, -SPSΔPS corrects for an error ΔPS in setting
P(k), which affects AD(k) through DUT’s sensitivity SPS to power setting errors. On the other
hand, A(k)'s in (5-4-1) are given by:
(5-4-3)
where ACAL is calibrated value of the attenuation step and is equal to (ACAL(1)+ACAL(2))/2:
SAPWΔPW corrects for Att.2's power dependence; note that ΔPW here is power difference between
P(k) and PCAL both expressed in W (not in dBm): SAPLΔPL1 corrects for the effect that the setting
of Att.1 changes the polarization state of its output light by ΔPL1, which then affects attenuation
step of Att.2 through its polarization dependence. Temperature variation, which is found to
affect the values of both ADC(k) and A(k) seriously, are not corrected but its effect is treated as a
random error component in AD(k).
44
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-4-5. Measurement setup for the incremental attenuation method.
Fig.5-4-6. Nonlinearity (NL) of DUT power meter. P(0) is the reference power (P(0)=100uW in
the comparison measurements.
5.4.4. Uncertainties of Linearity Calibration
The uncertainties of NL(n)'s in (5-4-1) are calculated as the root-sum-square of UAD(n) and
n
UA(n), which represent uncertainties of
A
k 1
DC ( k ) and
n
 A(k ) ,
respectively. UAD(n) and
k 1
UA(n) are obtained by accumulating uncertainty components of ADC(k) and A(k) over k as
follows:
45
APMP.PR-S2 Fiber Optic Power Responsivity
(5-4-4)
(5-4-5)
where UAD, UPS, and UDPL are uncertainties of AD(k), SPSΔPS and SDPLΔPL2 in (5-4-2), while UAC,
UAPL, and U(SAPW) are uncertainties of ACAL, SAPLΔPL1 and SAPW in (5-4-3). Note that, UDPL, UAC,
and U(SAPW) are independent of k and thus that uncertainties involving them cannot be
calculated as the root-sum-square of corresponding uncertainties for each k-th step. The
contributions of these uncertainties to NL(n) for several power levels representative of very low
(pW), intermediate (nW – μW), and high (mW) powers are summarized as follows: At the
lowest power, by far the largest contribution comes from UAD, i.e., experimental deviations of
raw readings with DUT, which is due to the limit of S/N performance of DUT at very low
powers. For intermediate to high powers the largest uncertainty component is nUAC. At the
n
highest power level the second largest contribution, arising from U ( S APW )
 P
k 1
W
, also
becomes significant, which indicate the importance of selecting a less power-sensitive
attenuator as a function of power. For powers P(n) > -90 dBm (nW), the expanded uncertainty
increases almost linearly with the difference between P(n) and P(0). The linear variation of UNL
is due to the fact that nUAC in (5-4-5) is the dominant uncertainty component, as stated above.
Note that UAC is the calibration uncertainty of the Att.2's attenuation step, and this calibration
uncertainty arises mainly from uncertainties of temperature dependence of both Att.2 and the
standard power meter, shown in Fig.5-4-5. For power levels of APMP-PR.S2 comparison (1 μW
– 100 μW), main contribution to the uncertainty was arisen from UAC and UAD, while other
components of the uncertainties as described above were quite less than one tenth of those two
components. Therefore we considered only UAC and UAD for the uncertainty estimation. That is
reasonable because the uncertainty itself of linearity measurements (~ 0.01 %) is usually less
than one tenth of that of optical power responsivity calibration (~ 0.2 %).
Uncertainty due to temperature or wavelength dependence of APMP artifact was determined
using data about ambient temperature and center wavelength during the comparison
measurements as mentioned in the section for 100 μW calibration. The uncertainty due to such
environmental parameters at 1 μW was determined as
2  u because the NL between 1 μW
and 100 W was calculated through the results for 10 W and 100 μW. The uncertainty budgets
46
APMP.PR-S2 Fiber Optic Power Responsivity
for the linearity calibration of the APMP artifact are summarized in Table 5-4-8 – 5-4-15.
Using measured non-linearity NL (dB) for each power level, that is, 1 and 10 μW and
correction factors at 100 μW measured by previous experiment mentioned above, we can derive
the correction factors for 1 and 10 μW. The uncertainty for determining the correction factors
for 1 and 10 μW was calculated by combining the uncertainty to determine the correction
factors at 100 μW and that for the linearity calibration.
5.4.5. Correction factors and its uncertainties with data for environmental
parameters
5.4.5.1. 100 W
Used range of APMP artifact: 4 (=1 A) for 100 W
Type of LD source: ECL (External Cavity Laser)
5.4.5.2. 10 W
Used range of APMP artifact: 5 (=100 nA) for 10 W
Type of LD source: ECL (External Cavity Laser)
47
APMP.PR-S2 Fiber Optic Power Responsivity
5.4.5.3. 1 W
Used range of APMP artifact: 6 (=10 nA) for 1 W
Type of LD source: ECL (External Cavity Laser)
5.4.6. Uncertainty Budgets
Table 5-4-1: Uncertainty budget for the calibration measurement of APMP artifact for optical
fiber power at 100 W, 1550 nm with APMP patch cord (FC-1) using the NMIJ optical fiber
calorimeter.
48
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-2: Uncertainty budget for the calibration measurement of APMP artifact for optical
fiber power at 100 W, 1550 nm with NMIJ patch cord using the NMIJ optical fiber calorimeter.
Table 5-4-3: Uncertainty budget for the calibration measurement of APMP artifact for optical
fiber power at 100 W, 1310 nm with APMP patch cord (FC-1) using the NMIJ optical fiber
calorimeter.
49
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-4: Uncertainty budget for the calibration measurement of APMP artifact for optical
fiber power at 100 W, 1310 nm with NMIJ patch cord using the NMIJ optical fiber calorimeter.
Table 5-4-5: Derivation of uncertainty for temperature dependence of APMP artifact.
Table 5-4-6: Derivation of uncertainty for wavelength dependence of APMP artifact (1550nm).
50
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-7: Derivation of uncertainty for Wavelength dependence of APMP artifact (1310nm).
Table 5-4-8: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 10 – 100 W, 1550 nm with APMP patch cord (FC-1) using the NMIJ linearity
calibration system for fiber optic power meter.
51
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-9: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 1 – 100 W, 1550 nm with APMP patch cord (FC-1) using the NMIJ linearity
calibration system for fiber optic power meter.
Table 5-4-10: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 10 – 100 W, 1550 nm with NMIJ patch cord using the NMIJ linearity calibration
system for fiber optic power meter.
52
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-11: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 1 – 100 W, 1550 nm with NMIJ patch cord using the NMIJ linearity calibration
system for fiber optic power meter.
Table 5-4-12: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 10 – 100 W, 1310 nm with APMP patch cord (FC-1) using the NMIJ linearity
calibration system for fiber optic power meter.
53
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-13: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 1 – 100 W, 1310 nm with APMP patch cord (FC-1) using the NMIJ linearity
calibration system for fiber optic power meter.
Table 5-4-14: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 10 – 100 W, 1310 nm with NMIJ patch cord using the NMIJ linearity calibration
system for fiber optic power meter.
54
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-4-15: Uncertainty budget for the linearity calibration of APMP artifact for optical fiber
power at 1 – 100 W, 1310 nm with NMIJ patch cord using the NMIJ linearity calibration
system for fiber optic power meter.
5.4.7. REFERENCES
[1] T. Inoue, I. Yokoshima and A. Hiraide, “Highly Sensitive Calorimeter for Microwatt-Level
Laser Power Measurements,” IEEE Trans. Instrum. Meas., vol. IM-36, no. 2, pp. 623-626,
Jun. 1987.
[2] S. Kodama, M. Horiuchi, T. Kunii and K. Kuroda, “Ultra-Black Nickel-Phosphorus Alloy
Optical Absorber,” IEEE Trans. Instrum. Meas., vol. 39, no. 1, pp. 230-232, Feb. 1990.
[3] Y. Suzuki, A. Murata, M. Aragai and T. Inoue, “Calorimeter with Compensative Absorber
for Measuring Microwatt Level Optical Power,” IEEE Trans. Instrum. Meas., vol. 40, no. 2,
pp. 219-221, Apr. 1991.
[4] “ISO, Guide to the Expression of Uncertainty in Measurement,” International Organization
for Standardization, Geneva, Switzerland, 1993.”
[5] I. Vayshenker, S. Yang, X. Li, and T.R. Scott, "Automated measurement of nonlinearity of
optical fiber power meters," in Proc. SPIE, Vol. 2550, pp. 12-19, 1995.
55
APMP.PR-S2 Fiber Optic Power Responsivity
5.5. NMIA
5.5.1. Measurement Setup and Method
5.5.1.1. Traceability:
5.5.1.2. Working Standard Detector
See NMIA APMP presentation on fibre power uncertainties from 2006 APMP TCPR workshop.
5.5.1.3. Comparison Setup
56
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.1.4. Method
Each source used was allowed a period of at least 1 hour to stabilise after activation before
measurements commenced.
The source wavelengths were measured by Yokogawa AQ6370 OSA s/n 91FC27793.
The effective wavelengths of each source were determined as described in Report RN070010.
The ILX Lightwave fibre optic power meter was manually set to the nearest integer value of
the effective wavelength determined for each source (or the wavelength setting was recorded
and later corrected to the response of the ILX at the nearest effective integer value of
wavelength).
The reference detector (TD3) was connected to a Keithley 486 picoammeter (s/n 0576891)
which was read via IEEE from a PC.
Similarly the ILX Lightwave was read via IEEE from the same PC.
For each meter range and wavelength tested:
1. Radiant flux levels were adjusted to values near the limit of each range tested using the
Anritsu attenuator.
2. The ILX range was selected manually.
3. NMIA laser power meter calibration software was run taking groups of 10 readings for
each of the detection systems beginning with zero levels for each detector (on the fixed
range to be calibrated for the ILX).
4. With the radiant flux propagating through fibre FC1, the patch cable was then
transferred between the reference detector TD3 and the ILX, exposing each detector for
a minimum of five sets of readings for each range tested, taking readings of the signal
current produced for the reference detector and the indicated power level for the ILX.
Note: For the reference detector measurements, patch cable FC1 was supported in a cork
lined chemical retention clamp so that the end was between 5 and 15 mm from the surface
of the reference detector and the axis of the fibre was at an angle between 2 and 8 degrees
from the normal to the surface of the detector to avoid inter-reflection errors. The
uncertainty in transfer from the multiple transfers performed will correspondingly contain
some component of the uncertainty from spatial non-uniformity and angular responsivity
variation because the fibre is aligned slightly differently each time.)
Selected ranges were recalibrated on different days to check previously determined results.
Uncertainty note:
NMIA Uncertainties for this intercomparison are dominated by noise introduced into the
57
APMP.PR-S2 Fiber Optic Power Responsivity
measurements by the NMIA Anritsu attenuator, which is not normally used for client
calibrations.
5.5.2. Measurement Results
The Laser Power Meter was tested to determine flux responsivity to fibre-optically propagated
coherent radiation at nominal wavelengths 1310 nm and 1550 nm using a fibre optic patch cord,
labelled “FC1”, terminated in a ceramic FC connector with end marked “out” to the detector.
Fig. 5-5-1. Spectral Distribution of NMI nominal 1310 nm laser source.
Fig. 5-5-2. Spectral Distribution of NMI nominal 1550 nm laser source.
The relative spectral radiant flux distributions for the laser sources are shown in Fig. 5-5-1
and 5-5-2. Using the data presented, the effective wavelengths for the sources, based on the
58
APMP.PR-S2 Fiber Optic Power Responsivity
responsivity weighting of the NMI reference InGaAs detector, were determined to be 1295.4 nm
and 1539.4 nm.
Using the laser sources described above, the results obtained for the responsivity of the Laser
Power Meter are given in Table 5-5-1.
Table 5-5-1. Results for the Radiant Power Responsivity of ILX FPM-8210 s/n 82103878 using
fibre optic patch cable “FC-1”.
59
APMP.PR-S2 Fiber Optic Power Responsivity
60
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3. Uncertainty Budgets
5.5.3.1. 100 W at 1295 nm (Range 3)
61
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.2. 100 W at 1295 nm (Range 4)
62
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.3. 10 W at 1295 nm (Range 4)
63
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.4. 10 W at 1295 nm (Range 5)
64
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.5. 1 W at 1295 nm (Range 5)
65
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.6. 1 W at 1295 nm (Range 6)
66
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.7. 100 W at 1539 nm (Range 3)
67
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.8. 100 W at 1539 nm (Range 4)
68
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.9. 10 W at 1539 nm (Range 4)
69
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.10. 10 W at 1539 nm (Range 5)
70
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.11. 1 W at 1539 nm (Range 5)
71
APMP.PR-S2 Fiber Optic Power Responsivity
5.5.3.12. 1 W at 1539 nm (Range 6)
72
APMP.PR-S2 Fiber Optic Power Responsivity
5.6. NML-SIRIM
5.6.1. Measurement Setup
This document sets out the results of NML-SIRIM, Malaysia in APMP key comparison of fiber
optic power responsivity. It also describes the description of the facilities involved as shown in
Fig. 5-6-1. The measurement is performed in a laboratory environmental conditions of (23  3)
C and (65  5) % R.H.. The measurement system consists of the items as listed in Table 5-6-1.
This calibration set-up covers the calibration of the artifact at the wavelengths of 1310 nm
and 1550 nm. Model IQ 1500 Calibration Power Meter manufactured by EXFO is used as
reference standard/national standard in order to carry out measurement on power meter. It has
reliable performance wise towards stability and also reproducibility.
The reference standard which being traceable to KRISS with absolute power reference
uncertainty 0.9 % for two wavelengths 1310 nm and 1550 nm. The national reference standards
are biennially calibrated at NIST until 2007. The traceability route now has been changed to
KRISS. Traceability chart as shown in Fig. 5-6-2.
1310 nm
DFBLD
Variable
Optical
Attenuator
1550 nm
DFBLD
Artefact
Artefact
Head
NML-SIRIM Working Standard
Fig. 5-6-1. Measurement system setup.
73
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-6-1. List of standards/equipment in the measurement system.
Equipment
Maker
Model
Serial #
Calibration Power Meter
Calibration Power Meter
Variable Attenuator
Splitter 1X2B
WDM Laser Source
WDM Laser Source
EXFO
EXFO
EXFO
EXFO
EXFO
EXFO
IQ 1500
IQ 1500
IQ 3100
IQ 9600
IQ 2400
IQ 2400
230777
230778
232087
232786
232279
204431
5.6.2. Traceability
NIST Since 2003
KRISS since 2007
Optical Power Meter at
1310 nm & 1550 nm
Power Meters
Fig. 5-6-2. Traceability chart.
5.6.3. Results
Wavelength,
Correction factor
Correction factor
Correction Factor
Expanded
nm
-10dBm
-20dBm
-30dBm
Uncertainty (%)
1310
1.0114
1.0108
1.0197
1.3
1550
1.0013
1.0018
1.0102
1.3
74
APMP.PR-S2 Fiber Optic Power Responsivity
5.6.4. Contribution towards expanded uncertainty
Source of Uncertainty
Value, %
Reference Power Meter
0.6
Spectral responsivity
0.5
Correction Factor
0.9
Power linearity
0.05
Power uncertainty
0.3
Power flatness
0.1
Expanded Uncertainty, k=2
1.3
75
APMP.PR-S2 Fiber Optic Power Responsivity
5.7. NIM
5.7.1. Main instrument used in the measurement
The Agilent 8164A lightwave measurement system is used as standard optical fiber power meter
which has been traced to NIM Cryogenic Radiometer. The detailed information of the 8164A
lightwave measurement system is shown in the table below:
Model
Description
Information (Measured by NIM)
81654A
LD Module
Central wavelength: 1301.4 nm/1543.4 nm
FWHM:
4.1 nm/5.6 nm
Stability(30min): ±0.002 dB/±0.002 dB
Peak wavelength uncertainty ：0.1 nm
81618A
Single Channel Interface/
Sensor InGaAs
Power Range :
(10 to -80) dBm
Linearity (0dBm to -40dBm): ±0.002 dB
81566A
Attenuator
Attenuation Adjust Range:
0 to 60 dB
5.7.2. Traceability
Fig. 5-7-1 shows the reference standard optical fiber power which is traceable to the NIM Laser
Cryogenic Radiometer based on the electrical substitution method. The laboratory standard is an
optical fiber power meter based on photodiode sensor. The optical fiber power meter (81618A)
is applied to carry out the comparison.
5.7.3. Environmental condition
The environment temperature is (21.6 ~ 23.1) ℃ and the humidity is (31 ~ 45) % in the
measurement process (6 days).
76
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-7-1. Traceability chain.
5.7.4. Results
5.7.4.1. Given FC/PC type fiber (FC-1)
Wavelength set
1301nm
1543nm
gain range
autorange
autorange
gain
Power Level
correction factor
4
0.1mW
1.0416
4
0.01mW
1.0421
5
0.001mW
1.0409
4
0.1mW
1.0335
4
0.01mW
1.0344
5
0.001mW
1.0330
77
APMP.PR-S2 Fiber Optic Power Responsivity
5.7.4.2. Given FC/PC type fiber (FC-2)
Wavelength set
1301nm
1543nm
gain range
autorange
autorange
gain
Power Level
correction factor
4
0.1 mW
1.0445
4
0.01 mW
1.0450
5
0.001 mW
1.0439
4
0.1 mW
1.0359
4
0.01 mW
1.0367
5
0.001 mW
1.0360
gain
Power Level
correction factor
4
0.1 mW
1.0442
4
0.01 mW
1.0434
5
0.001 mW
1.0433
4
0.1 mW
1.0359
4
0.01 mW
1.0368
5
0.001 mW
1.0354
5.7.4.3. NIM’s own FC/PC type fiber
Wavelength set
1301nm
1543nm
gain range
autorange
autorange
78
APMP.PR-S2 Fiber Optic Power Responsivity
5.7.5. Uncertainty Budgets
Source
Type
Standard
uncertainty
(%)
0.22
Uncertainty associated with the
reference standard used
uncertainty associated with the
source central wavelength offset
B
Repeatability of the measurement
A
0.1
Uncertainty associated with
linearity of the reference
standard used
Combined uncertainty
Expanded uncertainty (k=2)
B
0.06
Information
The laser source used in the
comparison is F-P type, which
central
wavelengths
are
1301.4nm and 1543.4nm. The
artifact(FPM-8240) wavelength
is set to 1301nm and 1543 nm in
the whole comparison process.
There is no correction to central
wavelength offset.
It
includes
uncertainty
associated with drift and
environmental condition viration
during the measurement process
（6 days）.
0.25
0.5
Note:
For the NIM laboratory standard is an optical fiber power meter based on photodiode sensor and
it directly read out the optical power, so there is no any uncertainty associated with the current
measurement.
79
APMP.PR-S2 Fiber Optic Power Responsivity
5.8. NIM (Second Measurements)
Since the comparison artifact was found to have large drift when it was checked by the pilot
after NIM’s measurements, NIM conducted second measurements after VNIIOFI’s
measurements. It was conducted two years later from the first measurements due to delivery
process and customs problem in Russia.
During NIM’s second measurements, significant artifact drift was observed even without
transportation. Therefore, the following report contains the results before and after drift.
5.8.1. Main instrument used in the measurement
The Agilent 8164A lightwave measurement system is used as reference standard optical fiber
power meter which has been traced to NIM Cryogenic Radiometer. The detailed information of
the 8164A lightwave measurement system is shown in the table below:
Model
Description
Information (Measured by NIM)
81654A
LD Module
81618A/81623A Single Channel Interface/
Sensor InGaAs
Central wavelength: 1301.2 nm/1542.4 nm
FWHM:
4.1 nm/5.6 nm
Stability(30min): ±0.002 dB/±0.002 dB
Central wavelength uncertainty ：0.1 nm
Power Range :
(10 to -80) dBm
Linearity (0 dBm to -40 dBm): ±0.002 dB
81566A
Attenuation Adjust Range:
Attenuator
(0 to 60) dB
5.8.2. Traceability
Fig. 5-8-1 shows the reference standard optical fiber power which is traceable to the NIM Laser
Cryogenic Radiometer based on the electrical substitution method. The laboratory standard is an
optical fiber power meter based on photodiode sensor. The optical fiber power meter (81618A)
is applied to carry out the comparison.
5.8.3. Environmental condition of the measurements
The environment temperature is (23 ~ 24) C
and the humidity is (25 ~ 29) % before drift and
(15 ~ 26) % after drift in the measurement process.
80
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 5-8-1. Traceability chain.
5.8.4. Measurement Results
5.8.4.1. Before drift
gain range
FC-1
FC-2
NIM fiber
autorange
100
1.0651
1.0711
1.0699
4
10
1.0644
1.0693
1.0679
5
1
1.0690
1.0735
1.0719
100
1.0575
1.0605
1.0590
4
10
1.0553
1.0592
1.0571
5
1
1.0600
1.0625
1.0604
gain
1301nm
4
1542nm
Correction factor of artifact
Power
Level（μW）
Wavelength
set
4
autorange
81
APMP.PR-S2 Fiber Optic Power Responsivity
5.8.4.2. After drift
gain range
FC-1
FC-2
NIM fiber
autorange
100
1.0764
1.0825
1.0813
4
10
1.0758
1.0807
1.0792
5
1
1.0804
1.0850
1.0833
100
1.0679
1.0709
1.0695
4
10
1.0657
1.0696
1.0676
5
1
1.0704
1.0730
1.0708
Relative
standard
uncertainty
Degree
of
freedom
gain
1301nm
4
1542nm
Correction factor of artifact
Power
Level（μW）
Wavelength
set
4
autorange
5.8.5. Uncertainty Budgets
5.8.5.1. Before drift
Source of uncertainty
Correction factor of
reference standard
Correction factor at
cal. wavelength
Ratio of ref.std. to
artifact
Reproducibility
(5 groups and 3
observers)
Source stability
Linearity of reference
standard
Relative Combined
Uncertainty
Relative
standard
uncertainty
Probability
distribution
Sensitivity
coefficient
0.32
%
normal
1
0.32
%
51
0.1
%
t
1
0.1
%
14
0.06
%
rectangular
1
0.06
%
100
0.04
%
rectangular
1
0.04
%
60
0.343
%
64
0.69
%
Relative Expanded Uncertainty ( Coverage factor: k = 2)
82
APMP.PR-S2 Fiber Optic Power Responsivity
5.8.5.2. After drift
Source of uncertainty
Relative
standard
uncertainty
Probability
distribution
Sensitivity
coefficient
Relative
standard
uncertainty
Degree
of
freedom
Correction factor of
reference standard
Correction factor at
cal. wavelength
Ratio of ref.std. to
artifact
Reproducibility
(5 groups and 3
observers)
0.32
%
normal
1
0.32
%
51
0.1
%
t
1
0.1
%
14
Source stability
0.06
%
rectangular
1
0.06
%
100
Linearity of reference
standard
0.04
%
rectangular
1
0.04
%
60
Correction factor drift
0.14
%
rectangular
1
0.14
15
Relative Combined
Uncertainty
0.37
%
Relative Expanded Uncertainty ( Coverage factor: k = 2)
0.74
%
77
Note:
NIM reference standard is an optical fiber power meter with photodiode sensor and it directly
read out the optical power. There is no uncertainty component contributed by electric current
measurement.
83
APMP.PR-S2 Fiber Optic Power Responsivity
5.9. VNIIOFI
5.9.1. Laboratory Standard
The VNIIOFI primary standard is a compact thermal detector operating at room temperature
and capable of electrical calibration. It incorporates two sensitive cavity-type absorbers
(receiving and compensating) with a substitution heater for electrical calibration. Calibration is
accomplished by direct substitution of electrically injected power using techniques to reduce
drift in ambient conditions. A high fraction of the incident power is absorbed by the cavity with
little spectral dependence. Input to the detector is achieved trough an optical-fiber connector.
Reference:
S.V. Tikhomirov, A.I. Glasov, M.L.Kozatchenko, V.E Kravtsov, A.B. Svetlichny, I.Vayshenker,
T.R. Scott, D.I. Franzen.
Comparison of reference standards for measurements of optical-
fiber power. Metrologia, № 37, 2000, pp. 347-348.
5.9.2. Measurement Conditions
Source: ANDO AQ2140 with AQ4213(131/155) LD UNIT, Variable attenuator EXFO FVA-60B.
Patch cord: No 1.
Temperature: ( 23 ± 1 )　C
5.9.3. Measurement Results
Table 5-9-1. Comparison data at 1310 nm.
Number
1
2
3
4
5
6
7
8
9
10
VNIIOFI standard, W
106.36
106.32
106.4
106.36
106.47
106.47
106.29
107.41
107.52
107.42
Mean value
Standard deviation, %
ILX, W
101.38
101.38
101.37
101.43
101.45
101.49
101.35
102.23
102.38
102.27
84
PVNIIOFI / PILX
1.04912
1.04873
1.04962
1.04860
1.04948
1.04907
1.04874
1.05067
1.05021
1.05036
1.0495
0.022
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-9-2. Comparison data at 1550 nm.
Number
1
2
3
4
5
6
7
8
9
10
VNIIOFI standard, W
106.07
106.14
106.14
105.92
105.42
105.56
105.60
105.74
105.34
105.45
Mean value
Standard deviation, %
ILX, W
103.02
102.76
102.78
102.63
102.62
102.63
102.38
102.44
102.48
102.45
PVNIIOFI / PILX
1.02959
1.03290
1.03270
1.03209
1.02724
1.02855
1.03142
1.03223
1.02793
1.02930
1.0304
0.065
5.9.4. Wavelength Correction
Central wavelengths:
1308.8 nm and 1548.5 nm.
Table 5-9-3. Spectral responsivity of ILX.
 (nm)
S (%)
 (nm)
S (%)
1290
98,66
1530
100
1300
98,81
1540
98,83
1310
99,14
1550
98,48
1320
99,72
1560
98,42
1330
100
1570
97,83
Correction factor 1310 nm:
S(1308.8nm) / S(1310nm) = 0.99960
Correction factor 1550 nm:
S(1548.5nm) / S(1550nm) = 1.00053
Resulting ratio 1310 nm: 1.0490
Resulting ratio 1550 nm: 1.0309
85
APMP.PR-S2 Fiber Optic Power Responsivity
Table 5-9-4. Measurement uncertainties.
Source
Standard uncertainty
Repeatability
1310 nm
1550 nm
0.022
0.065
Laser stability
0.1% - B
Laser wavelength
0.05% - B
ILX spectral responsivity
0.1% - B
Connector
0.1% - B
Temperature stability
0.1% - B
Laboratory standard
0.085% - A
Laboratory standard
0.06% - B
-A
Table 5-9-5. Comparison results.
Wavelength, nm
Ratio
Standard deviation, %
Expanded
uncertainty, %
1310
1.0490
0.022
0.44
1550
1.0309
0.065
0.45
86
APMP.PR-S2 Fiber Optic Power Responsivity
6. Results and Discussions
6.1. Artifact Drift
Artifact drift was checked by the pilot after the artifact was delivered to the pilot from the
participating lab and before it was delivered to the next participating lab. Therefore, there were
10 data sets on the deviation of correction factor of the artifact at -10 dBm level for both 1310
nm and 1550 nm with respect to the reference detector of the pilot. Simultaneously, the working
standard of the pilot (the same model as the artifact) was also checked with respect to the
reference detector of the pilot in order to monitor how stably the scale was maintained at the
pilot.
Table 6-1-1 and 6-1-2 show the accumulative deviation of correction factors using the two
different fiber connectors and they are plotted in Fig. 6-1-1 and 6-1-2. From Fig. 6-1-1, we
could identify that a significant drift took place before and after NIM’s measurements in both
the first and the second measurements. As it was mentioned in NIM’s second measurement
results in the previous section, it also drifted during their measurements, which led to report the
results twice. However, since it was delivered to the pilot, the correction factors did not change
for a month or so.
Table 6-1-1. Artifact drift check results using the pilot’s own fiber connector.
Deviation of Correction
factor of Artifact (%)
Deviation of Correction
factor of working
standard of pilot (%)
1310 nm
1550 nm
1310 nm
1550 nm
1
0.00
0.00
0.000
2
0.08
0.12
3
0.66
4
Fiber
connector
Date
Remark
(checked
after this
NMI)
0.000
KRISS
2006-03-06
KRISS
0.002
0.156
KRISS
2006-04-27
NMISA
0.69
N/A
N/A
KRISS
2006-07-10
CMS
1.20
1.13
-0.062
0.106
KRISS
2006-09-27
NMC
5
0.62
0.51
0.027
0.027
KRISS
2006-11-30
NMIJ
6
0.67
0.64
-0.070
0.118
KRISS
2007-03-16
NMIA
7
0.59
0.56
-0.091
-0.039
KRISS
2007-07-09
NML
8
2.80
2.49
0.351
0.424
KRISS
2008-01-15
NIM
9
3.42
2.35
0.510
0.568
KRISS
2009-10-07
VNIIOFI
10
4.73
4.21
0.495
0.383
KRISS
2011-01-04
NIM
87
APMP.PR-S2 Fiber Optic Power Responsivity
Table 6-1-2. Artifact drift check results using the fiber connector labeled as FC-1.
Deviation of Correction factor of Artifact (%)
Fiber
connector
Date
Remark
(checked
after this
NMI)
1310 nm
1550 nm
1
0.00
0.00
FC-1
2006-03-06
KRISS
2
0.01
0.03
FC-1
2006-04-27
NMISA
3
0.63
0.59
FC-1
2006-07-10
CMS
4
1.15
1.13
FC-1
2006-09-27
NMC
5
0.61
0.55
FC-1
2006-11-30
NMIJ
6
0.70
0.67
FC-1
2007-03-16
NMIA
7
0.75
0.72
FC-1
2007-07-09
NML
8
2.76
2.44
FC-1
2008-01-15
NIM
9
3.36
2.76
FC-1
2009-10-07
VNIIOFI
10
4.79
4.20
FC-1
2011-01-04
NIM
Although the reason of the drift was not visible because the optical head was an integrating
sphere with its detector firmly fixed as shown in Fig. 3-1 and 3-2, it is clear that something
happened during the transportation to NIM or from NIM. It is also clear that the spectral
responsivity of the artifact was also changed after VNIIOFI although the drift in each
wavelength was not as significant as the one after NIM.
The correction factors of the working standard of the pilot did not show deviation beyond the
expanded uncertainty of the pilot in Fig. 6-1-1, which was a good evidence of stable
maintenance of the scale.
From Fig. 6-1-2, the effect of fiber connector difference was negligible at the pilot.
88
APMP.PR-S2 Fiber Optic Power Responsivity
Fig. 6-1-1. Accumulative deviation of correction factors of artifact and working standard of
KRISS using KRISS fiber connector.
Fig. 6-1-2. Accumulative deviation of correction factors of artifact for the two different fiber
connectors.
89
APMP.PR-S2 Fiber Optic Power Responsivity
6.2. Difference from Pilot
To calculate the difference of measured correction factors between each participant (index i) and
the pilot (index p), the two values of the pilot, before (p1) participant and after (p2) participant,
was averaged by
C ip 
Cip1  Cip 2
,
2
(6-2-1)
for two different wavelengths and three different power levels. Since the two values of the pilot
were measured only at -10 dBm level for both 1310 nm and 1550 nm, we applied the same
deviation between the two values at -10 dBm to the values at -20 dBm and -30 dBm as well.
The relative standard uncertainty of the averaged value Cip is then given by
u r (Cip ) 
u 
2
p
r ,co
 
 
1 p1 2 1 p 2
ur ,un  u r ,un
4
4

2
,
(6-2-2)
2
where u rp,co , u rp,1un , and u rp,un
are relative standard uncertainties of the correlated components
(scale uncertainty), uncorrelated components (transfer uncertainty) of measurements before
participant, and uncorrelated components of measurements after participant, respectively. Since
the uncorrelated components are much smaller than overall combined standard uncertainty of
the pilot from Table 4-6-1 and 4-6-2, we used the following assumption.
u r (Cip )  u r (Cip1 )  u r (Cip 2 )
(6-2-3)
The relative difference  i of correction factors between the participant i and the pilot is
then calculated by
i 
Ci
1
Cip
(6-2-4)
and its uncertainty u ( i ) by
u ( i )  u r2 (Ci ) 

1 p1
u r ,un
4

2


1 p2
u r ,un
4

2
 u r2,ad (Ci )
(6-2-5)
where ur ,ad (Ci ) denotes the additional uncertainty of the correction factor by the participant i
due to non-ideal characteristics of the artifact. We used the drift of the artifact for the
corresponding participant as the value of ur ,ad (Ci ) that can be calculated by Eq. (6-2-6).
u r ,ad (Ci ) 
C ip 2
1
Cip1
(6-2-6)
Again, we ignored the uncorrelated components of the pilot in Eq. (6-2-5) because they were
90
APMP.PR-S2 Fiber Optic Power Responsivity
negligible for all participants.
For the pilot lab (i=0),  0  0 and the uncertainty u ( 0 ) is calculated by
u ( 0 ) 
1
N
N
u
i 1
r
(Cip ) ,
(6-2-7)
which is the average total relative uncertainty of all measurements at the pilot lab. Since the
pilot did not evaluate the uncertainty every time that the drift was checked, the reported
uncertainty of the pilot was used for all measurements, which means u ( 0 )  ur (C pilot ) .
The calculated results are summarized in Table 6-2-1 ~ 6-2-6 and Fig. 6-2-1 ~ 6-2-3. Please
note that we only used the data measured using the fiber connector labeled as FC-1 in
calculation. Later, we discussed about the effect of fiber connector.
Table 6-2-1. Difference from Pilot (1310 nm, -10 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
NMISA
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
VNIIOFI
NIM(2)
1.0116
1.016
1.027
1.0309
1.0287
1.0278
1.0114
1.0416
1.0490
1.0651
1.0116
1.0117
1.0149
1.0206
1.0205
1.0183
1.0190
1.0294
1.0426
1.0529
0.00368
0.00315
0.00690
0.00820
0.00247
0.00368
0.00650
0.00250
0.00220
0.00343
0
0.000125
0.006180
0.005116
0.005253
0.000880
0.000456
0.019996
0.005817
0.013861
0.0000
0.0042
0.0119
0.0101
0.0080
0.0093
-0.0074
0.012
0.0061
0.012
0.0037
0.0032
0.0093
0.0097
0.0058
0.0038
0.0065
0.0202
0.0062
0.014
Table 6-2-2. Difference from Pilot (1310 nm, -20 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
NMISA
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
NIM(2)
1.0104
1.016
1.025
1.0307
1.0279
1.0259
1.0108
1.0421
1.0651
1.0104
1.0105
1.0137
1.0194
1.0193
1.0171
1.0178
1.0282
1.0516
0.00374
0.00550
0.00690
0.00820
0.00307
0.00317
0.00650
0.00250
0.00343
0
0.000125
0.006180
0.005116
0.005253
0.000880
0.000456
0.019996
0.013861
0.0000
0.0055
0.0112
0.0111
0.0085
0.0087
-0.0068
0.014
0.012
0.0037
0.0055
0.0093
0.0097
0.0061
0.0033
0.0065
0.020
0.014
91
APMP.PR-S2 Fiber Optic Power Responsivity
Table 6-2-3. Difference from Pilot (1310 nm, -30 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
NIM(2)
1.0119
1.020
1.0301
1.0298
1.0282
1.0197
1.0409
1.0690
1.0119
1.0152
1.0209
1.0208
1.0186
1.0193
1.0297
1.0532
0.00368
0.00690
0.00820
0.00356
0.00323
0.00650
0.00250
0.00343
0
0.006180
0.005116
0.005253
0.000880
0.000456
0.019996
0.013861
0.0000
0.0047
0.0090
0.0088
0.0094
0.0004
0.011
0.015
0.0037
0.0093
0.0097
0.0063
0.0033
0.0065
0.020
0.014
Table 6-2-4. Difference from Pilot (1550 nm, -10 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
NMISA
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
VNIIOFI
NIM(2)
0.9948
1.002
1.014
1.0199
1.0148
1.0240
1.0013
1.0335
1.0309
1.0575
0.9948
0.9950
0.9979
1.0034
1.0032
1.0009
1.0018
1.0106
1.0207
1.0295
0.00389
0.00415
0.00580
0.00820
0.00258
0.00552
0.00650
0.00250
0.00225
0.00343
0
0.000347
0.005544
0.005380
0.005715
0.001189
0.000512
0.017045
0.003116
0.014005
0.0000
0.0070
0.0161
0.0164
0.0115
0.0230
-0.0005
0.023
0.0100
0.027
0.0039
0.0042
0.0080
0.0098
0.0063
0.0056
0.0065
0.017
0.0038
0.014
Table 6-2-5. Difference from Pilot (1550 nm, -20 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
NMISA
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
NIM(2)
0.9932
1.005
1.010
1.0196
1.0140
1.0245
1.0018
1.0344
1.0553
0.9932
0.9934
0.9963
1.0018
1.0016
0.9993
1.0002
1.0089
1.0278
0.00400
0.00700
0.00580
0.00820
0.00314
0.00445
0.00650
0.00250
0.00343
0
0.000347
0.005544
0.005380
0.005715
0.001189
0.000512
0.017045
0.014005
0.0000
0.0117
0.0137
0.0178
0.0124
0.0252
0.0016
0.025
0.027
0.0040
0.0070
0.0080
0.0098
0.0065
0.0046
0.0065
0.017
0.014
Table 6-2-6. Difference from Pilot (1550 nm, -30 dBm).
Participant
Ci
Cip
ur (Ci )
ur ,ad (Ci )
i
u ( i )
KRISS
CMS/ITRI
NMC-A*STAR
NMIJ/AIST
NMIA
NML-SIRIM
NIM
NIM(2)
0.9945
1.006
1.0186
1.0158
1.0290
1.0102
1.0330
1.0600
0.9945
0.9976
1.0030
1.0029
1.0006
1.0014
1.0102
1.0291
0.00389
0.00580
0.00820
0.00361
0.00747
0.00650
0.00250
0.00343
0
0.005544
0.005380
0.005715
0.001189
0.000512
0.017045
0.014005
0.0000
0.0084
0.0155
0.0129
0.0284
0.0088
0.023
0.030
0.0039
0.0080
0.0098
0.0068
0.0076
0.0065
0.017
0.014
92
APMP.PR-S2 Fiber Optic Power Responsivity
0.05
0.06
1310 nm, -10 dBm
Difference from pilot
Difference from pilot
0.06
0.04
0.03
0.02
0.01
0.00
-0.01
0.04
0.03
0.02
0.01
0.00
-0.01
-0.02
N
N
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
VN IM
IIO
N FI
IM
(2
)
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
I
M
VN
IIO
N FI
IM
(2
)
-0.02
1550 nm, -10 dBm
0.05
Fig. 6-2-1. Difference of correction factors of participants from the pilot at -10 dBm.
0.05
0.06
1310 nm, -20 dBm
Difference from pilot
Difference from pilot
0.06
0.04
0.03
0.02
0.01
0.00
-0.01
1550 nm, -20 dBm
0.04
0.03
0.02
0.01
0.00
-0.01
-0.02
N
N
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
I
M
VN
IIO
N FI
IM
(2
)
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
VN IM
IIO
N FI
IM
(2
)
-0.02
0.05
Fig. 6-2-2. Difference of correction factors of participants from the pilot at -20 dBm.
0.06
1310 nm, -30 dBm
Difference from pilot
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
0.05
1550 nm, -30 dBm
0.04
0.03
0.02
0.01
0.00
-0.01
-0.02
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
VN IM
IIO
N FI
IM
(2
)
KR
IS
S
M
IS
A
C
M
S
N
M
C
N
M
IJ
N
M
IA
N
M
L
N
I
M
VN
IIO
N FI
IM
(2
)
-0.02
N
N
Difference from pilot
0.06
Fig. 6-2-3. Difference of correction factors of participants from the pilot at -30 dBm.
93
APMP.PR-S2 Fiber Optic Power Responsivity
6.3. Comparison Reference Value
In calculation of comparison reference value, that is SCRV (supplementary comparison
reference value), we chose NIM’s second result only because the artifact drift was less in the
second measurement than the first one as shown in Fig. 6-1-2 (FC-1).
At first, the cut-off value of the uncertainty is determined by
u cut off  averageu r Ci  for u r Ci   medianu r Ci  (i  0 to N ) ,
(6-3-1)
where N is the number of participants excluding the pilot.
Then the reported uncertainty of each NMI is adjusted by the cu-off as
u r ,adj (Ci )  u r Ci 
u r ,adj (Ci )  u cut off
u r Ci   u cut off
for
u r Ci   u cut off
(i  0 to N ) .
(6-3-2)
The uncertainty of the relative difference  i after cut-off is also adjusted by
u adj ( i )  u r2,adj (Ci )  uT2 ( i )
(6-3-3)
where the transfer uncertainty component, uT ( i ) in u ( i ) is separated by
uT ( i )  u 2 ( i )  u r2 (Ci ) .
(6-3-4)
The weights wi is then calculated by
N
2
2
wi  u adj
( i ) /  u adj
( j ) .
(6-3-5)
j 0
Now the SCRV,  SCRV is determined by
N
 SCRV   wi  i ,
(6-3-6)
i 0
and the uncertainty of the SCRV is given by
u 2 ( i )
u  SCRV    4
i  0 u adj (  i )
N
N
u
i 0
2
adj
( i ) ,
(6-3-7)
and the expanded uncertainty of the SCRV is U ( SCRV )  ku ( SCRV ) (k=2).
The calculated values are summarized in Table 6-3-1 ~ 6-3-6 based on the summarized results
in Table 6-2-1 ~ 6-2-6.
94
APMP.PR-S2 Fiber Optic Power Responsivity
Table 6-3-1. SCRV and its uncertainty (1310 nm, -10 dBm). u cut off =0.00310.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0037
0.00368
0.0037
0.2140
NMISA
0.0042
0.0032
0.00315
0.0032
0.2916
CMS
0.0119
0.0093
0.00690
0.0093
0.0338
NMC
0.0101
0.0097
0.00820
0.0097
0.0310
NMIJ
0.0080
0.0058
0.00310
0.0061
0.0779
NMIA
0.0093
0.0038
0.00368
0.0038
0.2025
NML
-0.0074
0.0065
0.00650
0.0065
0.0683
NIM
0.0116
0.0143
0.00343
0.0143
0.0142
VNIIOFI
0.0061
0.0062
0.00310
0.0066
0.0667
 SCRV
U ( SCRV )
0.0045
0.0034
Table 6-3-2. SCRV and its uncertainty (1310 nm, -20 dBm). u cut off =0.00335.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0037
0.00374
0.0037
0.2706
NMISA
0.0055
0.0055
0.00550
0.0055
0.1250
CMS
0.0112
0.0093
0.00690
0.0093
0.0441
NMC
0.0111
0.0097
0.00820
0.0097
0.0405
NMIJ
0.0085
0.0061
0.00335
0.0062
0.0975
NMIA
0.0087
0.0033
0.00335
0.0035
0.3150
NML
-0.0068
0.0065
0.00650
0.0065
0.0891
NIM
0.0122
0.0145
0.00343
0.0145
0.0181
 SCRV
U ( SCRV )
0.0048
0.0038
Table 6-3-3. SCRV and its uncertainty (1310 nm, -30 dBm). u cut off =0.00348.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0037
0.00368
0.0037
0.3249
CMS
0.0047
0.0093
0.00690
0.0093
0.0513
NMC
0.0090
0.0097
0.00820
0.0097
0.0471
NMIJ
0.0088
0.0063
0.00356
0.0063
0.1093
NMIA
0.0094
0.0033
0.00348
0.0036
0.3424
NML
0.0004
0.0065
0.00650
0.0065
0.1036
NIM
0.0150
0.0143
0.00348
0.0143
0.0215
95
 SCRV
U ( SCRV )
0.0052
0.0041
APMP.PR-S2 Fiber Optic Power Responsivity
Table 6-3-4. SCRV and its uncertainty (1550 nm, -10 dBm). u cut off =0.00326.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0039
0.00389
0.0039
0.2346
NMISA
0.0070
0.0042
0.00415
0.0042
0.2047
CMS
0.0161
0.0080
0.00580
0.0080
0.0552
NMC
0.0164
0.0098
0.00820
0.0098
0.0369
NMIJ
0.0115
0.0063
0.00326
0.0066
0.0820
NMIA
0.0230
0.0056
0.00552
0.0056
0.1114
NML
-0.0005
0.0065
0.00650
0.0065
0.0835
NIM
0.0272
0.0144
0.00343
0.0144
0.0171
VNIIOFI
0.0100
0.0038
0.00326
0.0045
0.1746
 SCRV
U ( SCRV )
0.0086
0.0037
Table 6-3-5. SCRV and its uncertainty (1550 nm, -20 dBm). u cut off =0.00376.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0040
0.00400
0.0040
0.3040
NMISA
0.0117
0.0070
0.00700
0.0070
0.0990
CMS
0.0137
0.0080
0.00580
0.0080
0.0756
NMC
0.0178
0.0098
0.00820
0.0098
0.0506
NMIJ
0.0124
0.0065
0.00376
0.0068
0.1040
NMIA
0.0252
0.0046
0.00445
0.0046
0.2293
NML
0.0016
0.0065
0.00650
0.0065
0.1144
NIM
0.0268
0.0144
0.00376
0.0145
0.0231
 SCRV
U ( SCRV )
0.0110
0.0044
Table 6-3-6. SCRV and its uncertainty (1550 nm, -30 dBm). u cut off =0.00418.
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0039
0.00418
0.0042
0.3844
CMS
0.0084
0.0080
0.00580
0.0080
0.1045
NMC
0.0155
0.0098
0.00820
0.0098
0.0699
NMIJ
0.0129
0.0068
0.00418
0.0071
0.1341
NMIA
0.0284
0.0076
0.00747
0.0076
0.1175
NML
0.0088
0.0065
0.00650
0.0065
0.1582
NIM
0.0300
0.0144
0.00418
0.0146
0.0315
96
 SCRV
U ( SCRV )
0.0094
0.0050
APMP.PR-S2 Fiber Optic Power Responsivity
2
When the Chi-square value  obs
is calculated for consistency check using Eq. (6-3-8) where
i=0 represents the pilot lab,
N
 i   RV 2
i 0
2
u adj
( i )
2

 obs
,
(6-3-8)
the values are as shown in Table 6-3-7.
Table 6-3-7. Calculated Chi-square values.
Wavelength
(nm)
1310
1550
Power level
(dBm)
-10
-20
-30
-10
-20
-30
 (= N  1 )
2
 obs
2
 0.05
( )
7
6
5
7
6
5
8.105
7.604
4.880
16.995
20.964
14.012
14.067
12.592
11.070
14.067
12.592
11.070
2
2
  0.05
For the comparison results at 1310 nm, the consistency is satisfied because  obs
( ) for
all power levels. However, the consistency fails for the comparison results at 1550 nm because
2
2
 obs
  0.05
( ) . Therefore, we attempted to make the consistency satisfied in the case of 1550
nm by adding s 2 term in Eq. (6-3-3) following the Mandel-Paule method as
u adj ( i )  u r2,adj (Ci )  uT2 ( i )  s 2
(6-3-9)
2
2
  0.05
( ) .
and iteratively increase s from zero until  obs
The new SCRV and its uncertainty in the case of 1550 nm are summarized in Table 6-3-8 ~ 63-10 based on the new calculated u adj ( i ) . When we compare Table 6-3-4 ~ 6-3-6 and Table 63-8 ~ 6-3-10, we can notice that the SCRV increased by 5.1 %, 5.2 %, and 11.4 % for -10 dBm,
-20 dBm, and -30 dBm, respectively, with the uncertainty of SCRV almost unchanged.
97
APMP.PR-S2 Fiber Optic Power Responsivity
Table 6-3-8. SCRV and its uncertainty (1550 nm, -10 dBm). u cut off =0.00326.
2
s  0.00244,  obs
 14.067
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0039
0.00389
0.0046
0.2113
NMISA
0.0070
0.0042
0.00415
0.0048
0.1913
CMS
0.0161
0.0080
0.00580
0.0084
0.0633
NMC
0.0164
0.0098
0.00820
0.0101
0.0436
NMIJ
0.0115
0.0063
0.00326
0.0070
0.0905
NMIA
0.0230
0.0056
0.00552
0.0061
0.1177
NML
-0.0005
0.0065
0.00650
0.0070
0.0919
NIM
0.0272
0.0144
0.00343
0.0146
0.0208
VNIIOFI
0.0100
0.0038
0.00326
0.0051
0.1695
 SCRV
U ( SCRV )
0.0091
0.0037
Table 6-3-9. SCRV and its uncertainty (1550 nm, -20 dBm). u cut off =0.00376.
2
s  0.00388,  obs
 12.592
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0040
0.00400
0.0056
0.2387
NMISA
0.0117
0.0070
0.00700
0.0080
0.1155
CMS
0.0137
0.0080
0.00580
0.0089
0.0933
NMC
0.0178
0.0098
0.00820
0.0105
0.0666
NMIJ
0.0124
0.0065
0.00376
0.0079
0.1199
NMIA
0.0252
0.0046
0.00445
0.0060
0.2043
NML
0.0016
0.0065
0.00650
0.0076
0.1288
NIM
0.0268
0.0144
0.00376
0.0150
0.0329
 SCRV
U ( SCRV )
0.0115
0.0045
Table 6-3-10. SCRV and its uncertainty (1550 nm, -30 dBm). u cut off =0.00418.
2
s  0.00307,  obs
 11.070
Participant
i
u ( i )
u r ,adj (Ci )
u adj ( i )
wi
KRISS
0.0000
0.0039
0.00418
0.0052
0.3212
CMS
0.0084
0.0080
0.00580
0.0086
0.1171
NMC
0.0155
0.0098
0.00820
0.0103
0.0818
NMIJ
0.0129
0.0068
0.00418
0.0077
0.1451
NMIA
0.0284
0.0076
0.00747
0.0082
0.1297
NML
0.0088
0.0065
0.00650
0.0072
0.1664
NIM
0.0300
0.0144
0.00418
0.0149
0.0387
98
 SCRV
U ( SCRV )
0.0104
0.0051
APMP.PR-S2 Fiber Optic Power Responsivity
6.4. Degree of Equivalence
The unilateral degree of equivalence (DoE) of the participant i is definded by
Di   i   SCRV ,
(6-4-1)
and the uncertainty of DoE is given by
 u 2 ( )
u i  u 2 ( i )  u 2 ( SCRV )  2 2 i
 u adj ( i )
N
u
j 0
2
adj

( i ) ,

(6-4-2)
and
U i  kui
(6-4-3)
with the coverage factor k=2 at the level of confidence of approximately 95 %.
Table 6-4-1 and 6-4-2 summarize the calculation results and they are plotted in Fig. 6-4-1 and
6-4-6.
Table 6-4-1. Unilateral degree of equivalence and its uncertainty of each participant at 1310 nm.
Participant
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
1310 nm, -10 dBm
Di (%)
Ui (%)
-0.45
0.65
-0.03
0.53
0.74
1.8
0.55
1.9
0.35
1.1
0.48
0.67
-1.2
1.3
0.71
2.8
0.16
1.2
1310 nm, -20 dBm
Di (%)
Ui (%)
-0.48
0.63
0.07
1.0
0.64
1.8
0.63
1.9
0.37
1.2
0.39
0.55
-1.2
1.2
0.74
2.9
1310 nm, -30 dBm
Di (%)
Ui (%)
-0.52
0.60
-0.05
0.38
0.36
0.42
-0.48
0.98
1.8
1.9
1.2
0.56
1.2
2.8
Table 6-4-2. Unilateral degree of equivalence and its uncertainty of each participant at 1550 nm.
Participant
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
1550 nm, -10 dBm
Di (%)
Ui (%)
-0.91
0.70
-0.20
0.75
0.70
1.5
0.74
1.9
0.25
1.2
1.4
1.1
-0.95
1.2
1.8
2.9
0.093
0.73
1550 nm, -20 dBm
Di (%)
Ui (%)
-1.2
0.73
0.013
1.3
0.22
1.5
0.63
1.9
0.084
1.2
1.4
0.84
-0.99
1.2
1.5
2.8
99
1550 nm, -30 dBm
Di (%)
Ui (%)
-1.0
0.69
-0.20
0.51
0.25
1.8
-0.17
2.0
1.5
1.9
1.2
1.4
1.2
2.8
APMP.PR-S2 Fiber Optic Power Responsivity
4.0%
1310 nm, -10 dBm
3.0%
Unilateral DoE
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-1. Unilateral degree of equivalence and its uncertainty of each participant (1310 nm, 10 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
4.0%
1310 nm, -20 dBm
3.0%
Unilateral DoE
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-2. Unilateral degree of equivalence and its uncertainty of each participant (1310 nm, 20 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
100
APMP.PR-S2 Fiber Optic Power Responsivity
5.0%
1310 nm, -30 dBm
4.0%
Unilateral DoE
3.0%
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-3. Unilateral degree of equivalence and its uncertainty of each participant (1310 nm, 30 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
6.0%
5.0%
1550 nm, -10 dBm
Unilateral DoE
4.0%
3.0%
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-4. Unilateral degree of equivalence and its uncertainty of each participant (1550 nm, 10 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
101
APMP.PR-S2 Fiber Optic Power Responsivity
5.0%
4.0%
1550 nm, -20 dBm
Unilateral DoE
3.0%
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-5. Unilateral degree of equivalence and its uncertainty of each participant (1550 nm, 20 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
6.0%
5.0%
1550 nm, -30 dBm
Unilateral DoE
4.0%
3.0%
2.0%
1.0%
0.0%
-1.0%
-2.0%
-3.0%
KRISS
NMISA
CMS
NMC
NMIJ
NMIA
NML
NIM
VNIIOFI
Participant
Fig. 6-4-6. Unilateral degree of equivalence and its uncertainty of each participant (1550 nm, 30 dBm). Red dotted lines indicate the uncertainty boundaries of SCRV.
102
APMP.PR-S2 Fiber Optic Power Responsivity
6.5. Discussions
6.5.1. Range discontinuity
When we collected the reported values to make Table 6-2-1 ~ 6-2-6, we tried to compare the
values with the same gain range of the artifact at each optical power levels. However, there were
the cases that this was not so available. Table 6-5-1 shows the gain range of the artifact used by
each participant when it measured the values reported at different optical power levels for both
wavelengths.
Table 6-5-1. Gain range of the artifact reported by each participant.
Participant
Range at -10 dBm
Range at -20 dBm
Range at -30 dBm
KRISS
4
5
6
NMISA
4
5
N/A
CMS/ITRI
3 or 4 (not specified)
4 or 5 (not specified)
5 or 6 (not specified)
NMC-A*STAR
3
4
5
NMIJ/AIST
4
5
6
NMIA
4
5
6
NML-SIRIM
3 or 4 (not specified)
4 or 5 (not specified)
5 or 6 (not specified)
NIM
4
4
5
VNIIOFI
4
N/A
N/A
When the pilot measured the same stable optical power with the two different ranges of the
artifact, the displayed values show deviations of less than 0.2 % at all optical power levels and
wavelengths. It agrees with the values reported by NMIA, where they reported two correction
factors with different range at each optical power level for each wavelength.
Therefore, we can conclude that the range discontinuity did not significantly affect SCRV’s
and the unilateral DoE’s.
6.5.2. Effect of fiber optic connector
Six participants reported their correction factors measured with their own fiber connector as
well as FC-1. Note that FC-2 was prepared as a backup in case of damage of FC-1, but the
quality of FC-1 was sustained until the end of measurements so we did not include the case of
FC-2 here. The relative deviation of correction factor in case of FC-1 from that of NMI’s own
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APMP.PR-S2 Fiber Optic Power Responsivity
fiber connector for each participant at each optical power level and wavelength was summarized
in Table 6-5-2.
The maximum deviation was -0.49 % but it was well within 0.3 % for most cases as shown
in the table. Consequently, the effect of using different fiber connectors is well under the
uncertainty of fiber optic power meter calibration for all participants.
Table 6-5-2. Relative deviation of correction factor in the case of FC-1 from that of NMI’s own
fiber connector.
Relative deviation of correction factor (%):
Participant
Ci ,FC-1 / Ci ,own  1
1310 nm
-10 dBm
1310 nm
-20 dBm
1310 nm
-30 dBm
1550 nm
-10 dBm
1550 nm
-20 dBm
1550 nm
-30 dBm
KRISS
-0.25
-0.25
-0.25
-0.25
-0.25
-0.25
CMS
-0.19
N/A
N/A
-0.49
N/A
N/A
NMC
-0.19
-0.16
-0.16
0.05
0.15
0.08
NMIJ
-0.18
-0.17
-0.16
-0.12
-0.12
-0.12
NIM-1st
-0.25
-0.12
-0.23
-0.23
-0.23
-0.23
NIM-2nd
-0.45
-0.33
-0.27
-0.14
-0.17
-0.04
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APMP.PR-S2 Fiber Optic Power Responsivity
7. Conclusions
We have reported the results of the supplementary comparison of APMP TCPR on fiber optic
power responsivity at optical power levels of -10 dBm, -20 dBm, and -30 dBm and at
wavelengths of 1310 nm and 1550 nm.
We selected an artifact with an integrating sphere type optical head in order to suppress
polarization dependence and to reduce multiple reflection, which might unfortunately lead to
large drift in the later part of this comparison. Relatively large uncertainty of DoE compared to
the reported uncertainty of each participant was mainly due to the artifact drift. Another bad
thing was that we were unable to look inside the optical head and determine what was wrong in
the artifact. In order to examine the cause of the drift, destruction of the optical head may be
inevitable.
Although our choice of artifact was not quite satisfactory, we obtained quite consistent result
for comparison at 1310 nm. In case of 1550 nm, relatively larger deviations of DoE than 1310
nm were observed, which indicated that an effort is required to improve the scale by finding out
unknown sources of uncertainty.
The degrees of equivalence calculated from the data are to be used within the framework of
the Mutual Recognition Arrangement, for example, as the supporting evidence for the item 7.1.0
of the CCPR service category that is Responsivity, Fiber optic power meter.
105