Apparatus of adjusting optical signal transmission timing

A station side communication device connected to a plurality of subscriber side communication devices via a light multiplex/demultiplex device and deciding an order of optical signal transmissions from the subscriber side communication devices and deciding and instructing a transmission start timing for starting transmission of an optical signal for each of the subscriber side communication devices, the station side communication device comprising:

• an optical signal monitor unit which monitors powers of optical signals received from the subscriber side communication devices;
• and
• a transmission permission unit which decides a transmission start timing for each of the subscriber side communication devices;
• wherein when an optical signal is received from a second subscriber side communication device after a first subscriber side communication device, the transmission permission unit decides a transmission start timing of the second subscriber side communication device according to a power of the optical signal of the first subscriber side communication device monitored by the optical signal monitoring unit.