ECEN5533 Modern Commo Theory
Lesson #25
9 March 2016
Dr. George Scheets
Read 4.9 – 4.10
 Reworked Design #1 due 11 March

 Extra

Credit Points are still unclaimed
Reworked Quiz #2 due 23 March
ECEN5533 Modern Commo Theory
Lesson #26
11 March 2016
Dr. George Scheets
Problems 4.11, 4.16
 Reworked Design #1 due today

 Extra

Credit Points are still unclaimed
Reworked Quiz #2 due 23 March
Fiber Optics...
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Fiber Optic Link Analysis for ON-OFF
noncoherent ASK
Thermal Noise on the Fiber is NOT a problem
Noiseless Detection
No pulse transmitted: No far side photons
Pulse transmitted: Number of far side photons
has discrete Poisson Distribution
Mistake occurs when pulse transmitted and
number of far side photons = 0.
Real World Detectors are plagued by thermal
noise
On-Off ASK using
Matched Filter Detection
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
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Noncoherent Fiber Optic System
 P(BE) = Q[(SNR/2)0.5], SNR into M.F.D.
Coherent RF System
 P(BE) = Q[(SNR/2)0.5], SNR into M.F.D.
 But Coherent System should be better!
On-Off ASK (Average Signal Power = A2/4 watts)
 Logic 1 = Acosωot & Logic 0 = 0
A2/4 watts into Photo Detector → A2/8 watts out
 To
match Coherent SNR for RF System
Non Coherent needs A2/2 watts into Photo Detector
3 dB hit
Channel Capacity
Symbol shape and rate impact Bandwidth
 M-Ary: M possible symbols transmitted

 Symbol
rate the same & shape similar?
Bandwidth is the same, bit rate increases.
 Power the same?
Receiver symbol detection errors more likely.

BW & SNR affect bps we can move.
Channel Capacity (C)
Bandwidth, Bit Rate, SNR, and BER related
 Channel Capacity defines relationship
C = Maximum reliable bit rate
C = W*Log2(1 + SNR) bps

Bandwidth sets the maximum Baud rate
Channel Capacity (C)
Bandwidth, Bit Rate, SNR, and BER related
 Channel Capacity defines relationship
C = Maximum reliable bit rate
C = W*Log2(1 + SNR) bps

Bandwidth sets the maximum Baud rate
SNR sets the maximum number of
different symbols (the "M" in M-ary)
Channel Capacity (C)

Silk Road
 Claim:

Tbps bit rate over
64 KHz Fiber Bandwidth
1012 = 64,000 Log2(1 + SNR)
 My
calculator can't generate a high enough SNR
 Bogus Claim…
Or maybe erroneous claim by presenter
1999 Silk Road Claim


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
If Presenter's Claim was correct…
Tbps fiber systems possible in 64 KHz
… then Stock Analyst Report…
"70% chance company will succeed"
… provides indications that…
Wall Street & American Financial System
Led by People Who Don't Know What They're
Doing
Additional Evidence
2001 Dot.Com Crash
2008 Housing Market Crash
Channel Capacity (C)

Silk Road
 Claim:

Tbps bit rate over
64 KHz Fiber Bandwidth
EMail from ex-student
 Claim:
> Tbps over Power Lines
Power Line Transformers
Image Source
Wikipedia
Power Lines act as Antennas
Source: http://www.doobybrain.com/2008/02/03/electromagnetic-fields-cause-fluorescent-bulbs-to-glow/
Channel Capacity (C)

Silk Road
 Claim:

EMail from ex-student
 Claim:

Tbps bit rate over
64 KHz Fiber Bandwidth
> Tbps over Power Lines
Local Stillwater Entrepreneurs
 Wanted
to research Gbps over Power Lines
Channel Capacity (C)
Bandwidth, Bit Rate, SNR, and BER related
 Channel Capacity defines relationship
C = Maximum reliable bit rate
C = W*Log2(1 + SNR) bps


System claims to beat C?
 Extraordinary
Claim
 Needs Extraordinary Proof