Response to Reviewers
Reviewer #1:
In the manuscript fabrication, characterization of side - polished SMF fiber are
presented. (Without and with Graphene layer). Subject is new and worthy of
investigation, especially in terms of new fiber sensors.
Below are listed issues:
1.
Fig. 2 - it will be convenient for readers to give more precise range - where signal is
changing very fast.
We apologize for this. Upon reviewing the manuscript, we realized that the presentation of
Figure 2 is not proper, and would lead to confusion due to the different timelines. We have
redrawn Figure 2 to make it clearer as follows:
(a)
(b)
(d)
(c)
(d)
Figure 2. Transmission loss against time polishing at different ∆y positions of a) ∆y= 900 µm, b) ∆y= 1000
µm, c) ∆y= 1200 µm and d) ∆y= 1400 µm.
In the redrawn Figure 2, all timescales start at 0.0 seconds, with the initial power set to 0
dB. It can be seen that for a value of ∆y= 900 µm, the drop in power from 0 dB occurs at
15.3 seconds, reaching -20 dB at 17.2 seconds. In the same manner, for ∆y values of 1000
µm, 1200 µm and 1400 µm, the drops in power begin at 12.1s, 22.6s and 32.2s respectively,
and reaches 90% of the initial power value at 13.4s, 24.3s and 34.8s seconds. It can
therefore be seen that the fastest polishing time is achieved for the case of ∆y= 1000 µm,
with the core being reached at 12.1 s and the polishing process completed at 13.4 s. For all
other ∆y values, it takes longer to reach to core, with the longest time to reach the core and
to complete the polishing process observed for the case of ∆y= 1400 µm.
This explanation is included in the text as follows:
“From Figure 2, it can be seen that at ∆y= 900 µm, the power of the test signal travelling
through the core begins to drop from the initial value of 0 dBm approximately 15.3 seconds
after the polishing process starts, and quickly reaches – 20 dBm after only 17.2 seconds.
At ∆y values of 1000 and 1200 µm, it takes 12.1 seconds and 22.6 seconds for the power
of the signal to begin to decrease after the polishing process begins, and for both cases
reaches a power level of -20 dBm after 1.3 and 1.7 seconds respectively. Finally, for the
∆y value of 1400 µm, the power begins to drop from 0 dBm approximately 32.2 seconds
after the polishing process starts, and is completed at -20 dBm after approximately 34.8
seconds.”
The revised manuscript is highlighted in red in Lines 17 to 26 of Page 4. The revised figure,
Figure 2 is also indicated in red.
2.
Fig. 8 - please add in label Celsius degree
We have added the label ‘Celsius Degree’ to Figure 8.
3.
Did Authors considered to obtain surface plasmon responanse by covering fiber
noble metals? This subject is Hot topic. Please mention about it in introduction
section by giving appropriate references.
We have taken the recommendation of the reviewer and added a discussion on the surface
plasmon response (SPR) on the SPF as follows:
“In addition to the afore-mentioned 2- and 3-dimensional materials, the surface plasmon
resonance (SPR) effect can also be induced onto the SPF through the interaction of free
electrons in a semitransparent noble metallic layer and the light of the signal propagating
through the SPF. By inducing the SPR effect onto the SPF, numerous sensing applications,
particularly for biological and chemical constituents can be realized (Zhao et. al. 2016, Lin
et. al 2007 and Esmaeilzadeh et. al. 2015).”
This is given in Lines 11 to 17 of Page 2 and is highlighted in red.
The additional references have also been included in the manuscript as follows:
[Zhao, J., Cao, S., Liao, C., Wang, Y., Wang, G., Xu, X., & Wang, Y. (2016). Surface
plasmon resonance refractive sensor based on silver-coated side-polished fiber. Sensors
and Actuators B: Chemical, 230, 206-211]
[ Lin, H. Y., Tsai, W. H., Tsao, Y. C., & Sheu, B. C. (2007). Side-polished multimode fiber
biosensor based on surface plasmon resonance with halogen light. Applied optics, 46(5),
800-806]
[Esmaeilzadeh, H., Arzi, E., Légaré, F., Rivard, M., & Hassani, A. (2015). A super
continuum characterized high-precision SPR fiber optic sensor for refractometry. Sensors
and Actuators A: Physical, 229, 8-14]
The added references are highlighted in red in the references section of the manuscript.
4.
Taking account above and scientific level of journal presented manuscript after
minor revision can be published in Optical and Quantum Electronics.
Reviewer #3:
The authors report on a novel method for making side-polished fibers by pressing the
polishing wheel against the fiber suspended above it. SPFs fabricated this way are
characterized to V-bending and temperature, showing full recovery of transmitted
power. The work is interesting, however some crucial information is missing in the text
and several points have to be clarified.
1.
The manuscript lacks proper comparison between proposed polishing method and
other methods already established. The authors should emphasize in which way the
proposed method is better than others, is it simpler, cheaper, or gives better results,
etc.
The polishing method in this work differs from other established methods by the inclusion
of the Δy parameter, which is the movement of the polishing wheel perpendicular to the
fiber being polished. In this aspect, the Δy parameter induces a small amount of pressure
onto the fiber being polished, optimizing the contact between the fiber and the polishing
wheel. Similar works, such as that by (Hussey et. al. 1988) and (Zhao et al. 2015) do not
take this factor into account, thus making the work advantageous as there is additional
control over the fabrication process. Therefore, the work here provides a better result than
other similar techniques.
This is given in the revised text as follows:
“The proposed approach takes into account the Δy parameter, which is the movement of
the polishing wheel perpendicular to the fiber being polished. In this manner, a small
amount of pressure is placed on the fiber being polished, optimizing the contact between
the fiber and the polishing wheel and making it advantageous over similar works such as
that done by (Hussey et. al. 1988) and (Zhao et al. 2015).”
This is given in Lines 2 to 7 of Page 3 and is highlighted in red.
2.
Why was the paper with grit 400 chosen for polishing the fibers? Did the authors
compare the results obtained with different grit sizes?
The grit size of the paper used in this work was the finest available, with all other grit size
giving a rougher polish. We were unable to compare the results that would have been
obtained with other grit sizes, but larger grit sizes would indeed increase the roughness of
the SPF’s surface, as detailed by (Zhao et. al).
We have mentioned this in the revised text as follows:
“The grit size is chosen over the other available grit sizes as a lower grit value will make
the surface rougher and affect the SPF. This, a grid size of 400 gives a very smooth polish.”
This is given in red in Lines 27 to 30 of Page 3 of the revised manuscript and is highlighted
in red.
3.
The authors claim "Δy position of 1000 μm is shown to provide the fastest polishing
time with the power observed to start dropping at by 12.1 s, indicating that the
polishing depth is closed to core". It is not clear what exactly the value 12.1 s
represents. From the timeline shown in fig. 2b it seems that for Δy = 1000 μm power
starts dropping at roughly 14 min 24 sec. On the other hand, for Δy = 1200 μm the
power starts dropping at roughly 11 min 25 sec. Why then authors claim the fastest
polishing time is provided by Δy position of 1000 μm? Please clarify.
We apologize for this. Upon reviewing the manuscript, we realized that the presentation of
Figure 2 is not proper, and would lead to confusion due to the different timelines. We have
redrawn Figure 2 to make it clearer. In the redrawn Figure 2, all timescales start at 0.0
seconds, with the initial power set to 0 dB. It can be seen that for a value of ∆y= 900 µm,
the drop in power from 0 dB occurs at 15.3 seconds, reaching -20 dB at 17.2 seconds. In
the same manner, for ∆y values of 1000 µm, 1200 µm and 1400 µm, the drops in power
begin at 12.1s, 22.6s and 32.2s respectively, and reaches 90% of the initial power value at
13.4s, 24.3s and 34.8s seconds. It can therefore be seen that the fastest polishing time is
achieved for the case of ∆y= 1000 µm, with the core being reached at 12.1 s and the
polishing process completed at 13.4 s. For all other ∆y values, it takes longer to reach to
core, with the longest time to reach the core and to complete the polishing process observed
for the case of ∆y= 1400 µm.
The redrawn Figure 2 is as follows:
(a)
(b)
(d)
(c)
(d)
Figure 2. Transmission loss against time polishing at different ∆y positions of a) ∆y= 900 µm, b) ∆y= 1000
µm, c) ∆y= 1200 µm and d) ∆y= 1400 µm.
This explanation is included in the text as follows:
“From Figure 2, it can be seen that at ∆y= 900 µm, the power of the test signal travelling
through the core begins to drop from the initial value of 0 dBm approximately 15.3 seconds
after the polishing process starts, and quickly reaches – 20 dBm after only 17.2 seconds.
At ∆y values of 1000 and 1200 µm, it takes 12.1 seconds and 22.6 seconds for the power
of the signal to begin to decrease after the polishing process begins, and for both cases
reaches a power level of -20 dBm after 1.3 and 1.7 seconds respectively. Finally, for the
∆y value of 1400 µm, the power begins to drop from 0 dBm approximately 32.2 seconds
after the polishing process starts, and is completed at -20 dBm after approximately 34.8
seconds.”
The revised manuscript is highlighted in red in Lines 17 to 26 of Page 4. The revised figure,
Figure 2 is also indicated in red.
Please note that a similar comment has been made by the other reviewer, and has been
addressed in the same manner.
4.
Why is the polishing time not monotonic with Δy? It seems that higher Δy means that
the polishing wheel is pressed stronger against the fiber and this should result in
faster polishing. However, the authors claim polishing is fastest for Δy = 1000 μm,
what is the explanation for this?
The volumetric removal rate of the fiber cladding that relates to the polishing time can be
described by the following formula (Tong et. al. 2006):
𝑑𝑉
= 𝐶𝑝 𝑣𝑠 𝐹𝑁
𝑑𝑡
(1)
where CΡ is Preston coefficient, 𝑣𝑠 is the surface speed between the fiber and polisher and
𝐹𝑁 is the normal grinding force. Thus, as Δy is set to 1000 μm, the normal grinding force
is increases also, leading to an increment in the volumetric removal rate as described in
equation 1. This pattern has been shown in Figure 2 as the time for the power drop when
Δy =900 is longer than that when Δy = 1000 μm. However, as the value of Δy increases
further to 1200 μm and 1400 μm, the time taken for the power to begin to drop is longer
than that when the value of Δy is 1000 μm. This is attributed to the increased friction
between the polishing wheel and the fiber as a higher Δy induces more pressure onto fiber,
thus increasing the friction as well. This in turn results in the speed of the polishing wheel
reducing as a result of the extra loading onto the 6V DC motor, thus reducing its RPM
even though the voltage remains fixed. As a result of this, the volumetric removal rate of
the fiber cladding is not monotic, and can be represented better as a bell curve.
This is given in detail as follows:
“The volumetric removal rate of the fiber cladding against the polishing time can be
described as (Tong et. al. 2006):
𝑑𝑉
= 𝐶𝑝 𝑣𝑠 𝐹𝑁
𝑑𝑡
(1)
whereby CΡ is Preston coefficient, 𝑣𝑠 is the surface speed between the fiber and polisher
and 𝐹𝑁 is the normal grinding force. This pattern is shown in Figure 2, whereby it takes
less time for the power of the test signal to drop when Δy = 1000 μm as compared to when
Δy =900 μm. However, above Δy = 1000 μm, the time taken for the power to begin to drop
is longer. This is attributed to the increased friction between the polishing wheel and the
fiber as a higher Δy induces more pressure onto fiber, thus increasing the friction as well.
This in turn results in the speed of the polishing wheel reducing as a result of the extra
loading onto the 6V DC motor, thus reducing its RPM even though the voltage remains
fixed.”
This is highlighted in red in Lines 1 to 11 of Page 5.
5.
Would be useful to know what is the distance between fiber core and polished surface
(in the thinnest point) in SPFs with different insertion losses. Can the authors
estimate it?
The distance between the core and the polished surface is approximately 37.3 μm when
the insertion loss is 1.5 dB, and 4.63 μm when the insertion loss is 5.3 dB.
This is indicated in red in the text in Lines 14 to 16 of Page 12 as follows:.
“The distance between the core and the polished surface is approximately 37.3 μm when
the insertion loss is 1.5 dB, and 4.63 μm when the insertion loss is 5.3 dB.”
6.
The reason for power changes marked with red on fig. 10 should be explained in
details.
When the GO-solution is drop-casted, the solution forms an artificial cladding around the
core, thus trapping more light within the core, and as it dries, it forms a thin film around
the exposed core, which is seen by the rising signal power. However, once the thin film
solidifies around the exposed core, loss is induced in the fiber as the GO molecules begin
to interact fully with the propagating signal. At this juncture, the power begins to drop.
Finally, the SPF is slowly lifted from the forming GO thin film, and the power stabilizes.
This is given in the revised text as follows in Lines 1 to 13 of page 12 and is highlighted
in red as follows:
“A possible explanation for this is that before the drop-casting of the GO solution, the core
of the SPF is exposed, allowing a substantial amount of light to leak out. At this juncture,
the power of the signal recorded is -27.5 dBm. When the GO-solution is drop-casted, the
solution forms an artificial cladding around the core, thus trapping more light within the
core. As the GO solution dries, it begins to form a thin film around the exposed core, which
is seen by the rising signal power. However, once the thin film solidifies around the
exposed core, loss is induced in the fiber as the GO molecules begin to interact fully with
the propagating signal. At this juncture, the power begins to drop. Finally, the SPF is
slowly lifted from the forming GO thin film, and the power stabilizes. In this manner, the
refractive index of the GO layer plays an important role whereby its index is higher as
compared to the core, and will strip the power away from the core.”
We have also amended the plot of Figure 10 to give a better view of the power once the
fiber has been completely removed. The revised figure is as follows:
GO starts to dry
hard
2.5 𝜇𝐿 drop-cast
session
Dried GO gel on SPF
Glass and fiber
separation
Glass and fiber has been completely separated
We hope that this is acceptable to the reviewer.