Effect of phase noise on the performance of coherent optical fiber communication system

The purpose of this work is to calculate the PSD (power spectral density) of 5B6B coded signals at the output of a PSK (phase shift keyed)/FM subcarrier heterodyne system. The influence of laser phase noise on the PSD has also been investigated. Experimental results indicate that as the laser linewidth decreases, a sharp peak is obtained at the frequency, f, equal to the sum of the IF and source oscillator frequency and the bandwidth of the signal at the output decreases. The value of PSD at f, for the linewidths of 10 MHz, 15 MHz and 20 MHz are 1.21*10/sup -18/ W/Hz 0.81*10/sup -18/ W/Hz and 0.607*10/sup -18/ W/Hz, respectively. This shows that the average power is greater when the laser linewidth decreases. The result obtained may be useful in the design of multichannel coherent communication systems.<
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