An overview of technical research on inter-channel nonlinearity power monitoring

• 1、School of Information and Communication Engineering，Beijing University of Posts and Telecommunications，Beijing 100876

Abstract：With the continuous growth of the communication service, the capacity of fiber-based bearer networks needs to be expanded constantly to meet the increase demand. Coherent optical communication with digital signal processing (DSP) algorithms has replaced the intensity modulation direct detection technology, and has become the major technology of the high-capacity and long-haul optical transmission systems. Linear impairments such as chromatic dispersion and polarization mode dispersion can be well equalized by DSP algorithms. However, there is no mature equalization algorithm for nonlinear effects. With the increase of transmission capacity and the decrease of the channel spacing, the impairment of inter-channel nonlinear effects on the signal becomes more serious in WDM systems. Inter-channel nonlinearity (NL) monitoring and equalization have become the focus of currently research. This paper reviews the research work on inter-channel NL monitoring. First, several major methods of inter-channel NL monitoring are introduced, as well as the principles, main application systems and the monitoring errors of these methods. Then, the method of the inter-channel NL monitoring with differential pilot (DP) is emphatically introduced and a simulation system is established for verification. The application scope problem of this method is pointed out to be further discuss. Finally, several major inter-channel NL monitoring methods are compared in terms of complexity, accuracy and practicability.

Keywords： Communication and Information System coherent optical communication system inter-channel nonlinearity differential pilot