Enhanced performance of in-band OSNR monitor based on delay time optimization of interferometer

We propose and experimentally demonstrate a method of choosing optical delay time by calculating normalized autocorrelation function of channel noise to achieve optimal OSNR monitoring performance. Up to 29 dB monitoring range with error ≤±0.5 dB for 112 Gbit/s PM-QPSK signal is obtained. We also demonstrate the method is applicable to the filters with different bandwidths and different shapes.