OSNR monitoring technique based on four-wave mixing for polarization-division multiplex transmission

We propose and demonstrate a novel OSNR monitoring technique for polarization division multiplexed (PDM) transmission. This technique based on four-wave mixing in nonlinear medium can individually monitor the OSNR values of X-axis and Y-axis signals in 80-Gbps PDM-NRZ transmission with accuracy of 0.5 dB.