Performance analysis of polarization-insensitive phase diversity optical FSK receivers

A polarization-insensitive phase-diversity optical frequency-shift-keying (FSK) receiver is proposed, and its performance is evaluated. The basic model and signal processing formulation are developed to describe the functions and features of this receiver. Two different approaches (one of which is an upper bound) are used to treat the mixed noise terms, and Gaussian approximation is employed to estimate the receiver performance in terms of the laser linewidth, the modulation index, and the filter bandwidth. The virtually polarization-insensitive property is also verified. As an example, numerical results are presented for a 150-Mb/s receiver, which show that the difference between the upper bound and the other approximation is about 2 to 3 dB. It is also shown that the receiver with small modulation index is less tolerant of the linewidth so that an error floor may appear. When the modulation index is large, the receiver can tolerate linewidths comparable with the bit rate