Frequency Estimation for Optical Coherent MPSK System Without Removing Modulated Data Phase

By investigating the spectrum property of the frequency offset in an optical coherent
M
-ary phase-shift-keying system, a frequency estimation is presented based on fast Fourier transform of the signal's argument. Different from the previous algorithms, it does not require removing modulated data phase. The principle of the algorithm is proven and a flowchart is proposed to illustrate the algorithm. Numerical simulations are performed to demonstrate the algorithm.