Blind Modulation Format Identification Using Differential Phase and Amplitude Ratio

We propose a blind digital modulation format identification (MFI) method for coherent optical fiber communication systems. Based on the evaluation of differential phase distribution ratio (DPDR) and average of amplitude ratio (AAR), a monitoring factor {R}, the product of DPDR and AAR, is defined to distinguish whether the signal modulation format is QPSK, 16-QAM, or 64-QAM. Simulation and experimental results demonstrate that the proposed MFI can perform an identification when the OSNR of the incoming signal is greater than 12 dB. The proposed method needs no extensive training data sets and can tolerate residual chromatic dispersion (-210-210 ps/nm) and phase noise.