Abstract
In this thesis we discuss the receiver performance of twotypes of optical coherent communication system, i.e., homodynePSK systems and heterodyne CPFSK systems . In the first part ofthis study, which deals with homodyne PSK systems, weemphasize the effect of signal waveform distortion on systemperformance, although other effects such as the effects oflaser phase noise and shot noise are accounted for . In contrastto the conventional discussion in which the received signaldata is a sequence of square pulses, this study for the firsttime investigates the problem encountered in BPSK homodynecommunication systems with Costas PLL's as the received signaldata is not a sequence of square pulses but is a sequence ofdistorted pulses . The signal waveform distortion inducesadditional amount of phase error variance and henceforth anincrease in bit-error rate, resulting in a more stringent laserlinewidth requirement . Ths laser linewidth requirement isevaluated here taking into account such an effect of signalwaveform distion . Then in the second part, we analyze thesystem performance of optical CPFSK receivers with AFC loops .The effects of loop gain, bandwidth of IF band-pass filter,and postdetection filters are taken into account . The KL(Karhunen-Loeve) expansion and the GQR ( Gaussian quadure rule )method are used to deal with the laser phase noisecharacteristics in computing the bit-error rates . Withdifferent closed loop gains, we show the improvement of systemperformance compared with the system without AFC .