Abstract

Continuous-phase frequency-shift keying (CPFSK) is an attractive modulation format for coherent optical communication systems.¹ CPFSK can be demodulated by means of differential detection (Fig. 1). This type of receiver combines improved sensitivity and circuit simplicity but it is sensitive to laser phase noise. However, its performance can be optimized by proper choice of receiver filters. In a previous paper we presented a method for optimizing the bandpass filter of the receiver.² In this paper, the effect of the postdetection (low-pass) filtering is, for the first time to our knowledge, accurately analyzed.

© 1995 Optical Society of America