Analysis of OSNR monitoring in optical fiber communication system

The transmission data rates of the next generation intelligent optical networks are high, and the applications of dense wavelength division multiplexing (DWDM) and reconfigurable optical add-drop multiplexer (ROADM) enable the traditional out-band optical signal-to-noise ratio (OSNR) monitoring techniques aren´t suitable. In this paper, three methods of out-band and in-band OSNR monitoring in optical fiber communication system are studied and compared, which are mainly based on traditional out-band interpolation, in-band on-off signal, and in-band polarization diversity approaches. The traditional out-band interpolation is not very accurate for the dynamic DWDM networks. The on-off signal method is simple and accurate but it will interrupt the service and not suitable for the real time monitoring. The polarization diversity method is some complicated but it can be applied for real time in-band OSNR monitoring in next generation optical networks.