Phase noise due to ASK amplitude un-equality and Kerr nonlinearity in optical ASK-DPSK, ASK-DQPSK systems

Phase noise due to ASK amplitude un-equality and Kerr nonlinearity is first investigated in this paper. Then, for the phase modulation path, the eye-diagram closure at the receiver end is observed with the impact of the phase noise. Finally, by analyzing the eye-opening penalty varying with extinction ratio for ASK-path and DPSK/DQPSK path signal at the balance receiver end, it reveals that the optimal extinction ratio varies with the input power. The conclusion is quite different from that the optimal extinction ratio is constant without consideration of the phase noise.