EFFECTS OF LOCAL OSCILLATOR EXCESS NOISE, LASER PHASE NOISE AND TIMEJITTER ON DIGITAL SIGNALING SCHEMES IN COHERENT OPTICAL FIBER COMMUNICATION-SYSTEMS

The paper investigates performance of heterodyne detection type coherent optical-fibre communication systems for binary and M-ary PSK, FSK and ASK digital signalling schemes, considering shot noise, local oscillator (LO) excess noise, laser phase noise and time jitter. Expressions for probability of error when LO excess noise, laser phase noise and time jitter are present as well as shot noise, are derived. Power penalties are also obtained in each case. Finally, the three signalling schemes are compared. The binary PSK is found to be the most efficient among the three signalling schemes. However, when laser phase noise is large, M-FSK and M-ASK signalling schemes give better performance than the M-PSK signalling scheme. The M-FSK scheme is found to require a larger bandwidth, and the M-ASK scheme is less immune to time jitter.