A modulation format identification method based signal amplitude sorting and ratio calculation

Modulation format identification (MFI) is an indispensable part of next generation optical networks such as elastic optical networks (EON). We propose a simple MFI method based on signal amplitude sorting and ratio calculation. After sorting the amplitude of signals, three MFI feature values are extracted to identify polarization division multiplexing (PDM) quadrature phase shift keying (PDM-QPSK) and three commonly used quadrature amplitude modulation (QAM) signals (PDM-16QAM, PDM-32QAM and PDM-64QAM). Numerical simulations verify the effectiveness of proposed MFI method with the required optical signal noise ratio (OSNR) lower than 7% forward error correction (FEC) threshold. Proof-of-concept experiments using QPSK, 16QAM, 32QAM and 64QAM signals with 100 km fiber transmission demonstrate the feasibility of proposed MFI method. We also investigate the influence of fiber transmission distance, fiber nonlinearity and symbol numbers on the proposed method and the results show that the proposed MFI methods can achieve accurate identification at different fiber transmission length, a range of fiber nonlinearity and small requirement of symbol number. The method is simple and insensitive to phase impairments caused by laser phase noise and frequency offset (FO), which will bring convenience into future EONs.