Phase-noise-canceled differential phase-shift-keying (PNC-DPSK) for coherent optical communication systems

A modulation scheme using a nonlinear demodulation process, phase-noise-canceled differential phase-shift keying (PNC-DPSK), is used to circumvent the effects of phase noise in a phase-shift keying (PSK) system. A theoretical description of the system is given, and results of an experimental test system are shown to be in good agreement with the predictions. In particular, it is shown that the phase-noise-induced bit error rate (BER) floor can be eliminated despite using lasers with linewidths comparable to the data rate. Furthermore, for an optimized PNC-DPSK system, the degradation at high signal-to-noise compared to heterodyne PSK with ideal sources (i.e. no phase noise) should only be ≈3 dB