COMMUNICATION MONITORING SYSTEM

Provided is a communication monitoring system capable of monitoring a state of a connection device that forms an optical path by using an optical passive component. A communication monitoring system (1) includes a plurality of photodetectors (9) provided in a connection device (6), a plurality of recognition units (13), a processing unit (14), a light emitting unit (15), a mixing unit (12), a separation unit (16), a collection unit (17), and a management unit (18). The photodetector (9) detects an optical signal passing through a corresponding optical path. The recognition unit (13) recognizes a state of detection by the corresponding photodetector (9). The processing unit (14) generates information regarding a communication state of the connection device (6) on the basis of the recognition by each recognition unit (13). The light emitting unit (15) converts the generated information into a monitoring signal that is an optical signal and transmits the monitoring signal. The monitoring signal is passed through an optical communication line (3) as a mixed signal by the mixing unit (12) and is separated from the mixed signal by the separation unit (16). The collection unit (18) outputs the separated monitoring signal to the management unit (18) that manages a state of a PON (2).