Optical transceiver, optical transmission system, and light source output monitoring method

An optical transceiver includes: a light source; a light source power management unit configured to manage a state of an output power of the light source; an optical detector configured to receive a first optical signal from a counterpart optical transmission apparatus and detect the first optical signal; and a monitoring information extraction unit configured to extract a monitoring information of a reception power level of a second optical signal, which is generated from an output light of the light source and received in the counterpart optical transmission apparatus, from the first optical signal, wherein the light source power management unit is configured to update a written value of the state of the output power of the light source in a case where a monitored value of the reception power level included in the monitoring information is decreased to exceed a variation of an optical transmission path.