Page 512 - Fiber Optic Communications Fund

Nonlinear Effects in Fibers 493

10.14 Two Gaussian pulses of width 40 ps separated by 25 ps are transmitted in a dispersion-free fiber over
80 km. Find the nonlinear phase shift at the center of either of the pulses at the fiber output. Assume
−1
= 2.2W −1 km , fiber loss = 0.2 dB/km, and peak power = 4mW.
(Ans: 0.466 rad.)

10.15 In a 10-Gb/s fiber-optic system based on BPSK operating at 1530 nm there are N in-line amplifiers
a
with a noise figure of 4.5 dB. NRZ rectangular pulses are used with a mean power of 0 dBm. The
−1
fiber parameters are as follows: = 2.2W −1 km −1 and = 0.0461 km . The variances of linear
2
2
and nonlinear phase noises at the fiber output are found to be 2.27 × 10 −3 rad and 3.98 × 10 −3 rad ,
respectively. Calculate the amplifier spacing. Ignore dispersion.
(Ans: 100 km.)
10.16 Discuss stimulated Raman scattering in optical fibers.
10.17 In a partially Raman amplified fiber-optic system, it is desired that the gain provided by the Raman
−1
pump is 10 dB. The Raman coefficient of the fiber = 1 × 10 −13 m/W, signal loss = 0.046 km ,
s
−1
2
pump loss = 0.09 km , length = 80 km, and effective area of the fiber = 80 μm . Assuming that
p
the pump co-propagates with the signal, calculate the input pump power.
(Ans: 431 mW.)
Further Reading

G.P. Agrawal, Nonlinear Fiber Optics, 3rd edn. Academic Press, San Diego, CA, 2001.
R.W. Boyd, Nonlinear Optics, 3rd edn. Academic Press, San Diego, CA, 2007.
Y.R. Shen, Principles of Nonlinear Optics. John Wiley & sons, Hoboken, NJ, 2003.
A. Hasegawa and M. Matsumoto, Optical Solitons in Fibers, 3rd edn. Springer-Verlag, Berlin, 2003.
N. Bloembergen, Nonlinear Optics, 4th edn. World Scientific, Singapore, 1996.
J.V. Moloney and A.C. Newell, Nonlinear Optics. Westview Press, Boulder, CO, 2004.

References
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Consultants Bureau, New York, 1984.
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