Subtraction-Clustering-Based Modulation Format Identification in Stokes Space

A Stokes-space-based modulation format identification (MFI) technique with low complexity is proposed for coherent optical receivers, on the basis of the subtraction clustering algorithm. Successful MFI with good optical signal-to-noise ratio performance can be realized among polarization-multiplexed BPSK, QPSK, 8PSK, 8QAM, and 16QAM signals. Experimental verifications are also performed to prove the feasibility of the proposed MFI in long-distance optical fiber transmission systems.