ece228 lecture16

ece228 lecture16 - Bowers ECE 228A Optical Amplification...

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Bowers ECE 228A Optical Amplification Lecture #16 John Bowers CE 228A ECE 228A Read Chapter 6
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Bowers ECE 228A Bit Error Rate (BER) robability of error = [0]P[1|0] + P[1]P[0|1] Probability of error P[0]P[1|0] + P[1]P[0|1] P[0] = Probability a “0” was transmitted P[1] = Probability a “1” was transmitted P[1|0] = Probability a “1” is received given that a “0” is transmitted [0|1] = Probability a “0” is received given that a “1” is transmitted P[0|1] Probability a 0 is received given that a 1 is transmitted DF for a “0” “1” Under the gaussian assumption:  1  0 PDF for a “1” transmitted PDF for a “0” transmitted P 1| 0  1 0 2 exp I 0 I 2 2 0 2 I D dI 2 <I 1 > <I 0 > I D Area = P[0|1] Area = P[1|0] P 0|1 1 12 exp I 1 I 2 1 2 I D dI I 15.2
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Bowers ECE 228A BER and Q-Factor 2 Q 0 I D I 0 0 Q 1 I D I 1 P 1|0  1 2 exp I 2 Q 0 dI P 0|1 1 2 exp I 2 2 Q 1 dI Substituting The “near” optimum decision threshold is I D 0 I 1  1 I 0 1 0   1 Defining the Q factor Q I 1 I 0 1 0 • BER is the most important performance indicator of a receiver • Q-factor is a good indicator The bit error rate (BER) assuming Gaussian noise can be written as   2 2 / exp 2 2 1 2 Q Q Q erfc BER 15.3
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Bowers ECE 228A BER vs. Q-Factor 10 -8 0 0 10 -12 10 -10 BER 9 10 12 10 10 -5 10 - 6 10 -14 10 -15 10 -10 15 15.5 16 16.5 17 17.5 18 10 16 Important values : • Q~16 dB -> BER=10 -9 Q [dB] (20 log 10 Q linear ) 0 1 2 3 4 5 6 7 8 9 0 10 -25 10 -20 • Q~17.0 dB-> BER=10 - 12 • slope: 2 decades per dB around BER=10 -9 lope increases when 15.4 10 11 12 13 14 15 16 17 18 19 20 Q [dB] (20 log 10 Q linear ) (slope increases when increasing reference BER)
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Bowers ECE 228A Critical Elements for Networks • Transmitters • Receivers • Amplifiers Optical Amplifiers • Switches • Add/drop multiplexers (ADMs, ROADMs) Wavelength multiplexers, demultiplexers • Polarization Controllers
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Bowers ECE 228A Optical Amplifiers • Preamp – Low noise critical • Power amplifier – High saturation power critical • In-line amplifier – Tradeoff noise and saturation power Remotely pumped amplifier
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Bowers ECE 228A Optical Amplifiers
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Bowers ECE 228A EDFA Design
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Bowers ECE 228A Critical Issues for Optical Amplifier Design Gain (10 to 40 dB) dP P z g dz ) ( ) exp( ) ( gz P z P in in out P P G ) ) ( exp( ) ( L g G 
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Bowers ECE 228A Critical Issues for Optical Amplifier Design Gain (10 to 40 dB) in out P P G dP p( z P z g dz ) ( ) ) ( exp( ) ( L g G  ) exp( ) ( gz P z P in
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ece228 lecture16 - Bowers ECE 228A Optical Amplification...

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