I. Introduction
To satisfy the increasing demand for communication bandwidth, we need to apply signals with high order modulation formats to develop the bandwidth efficiency, which makes optical networks more complex. And the reconfigurable optical add/drop multiplexer (ROADM) makes the systems dynamic and reconfigurable [1]. Monitoring the condition of signals to keep the quality of service (QoS) becomes a critical issue. Optical performance monitoring (OPM) technique can obtain various parameters of physical layers of fiber networks, such as modulation format (MF), baud rate (BR), launch power, optical signal-to-noise ratio (OSNR) of signals and so on. This information helps the management of smart reconfigurable software define network (SDN) [2].