Patent ID: 7505685

Claim:
An optical communication system having a plurality of optical communication apparatuses for transmitting a plurality of optical channels, of the plurality of optical communication apparatuses, a first optical communication apparatus which sends out optical channels, including: (a1) means for evaluating whether or not user data to be transmitted on an object one of the plurality of optical channels exists; and (a2) means for transmitting, if said evaluating means judges that user data to be transmitted on said object optical channel is absent, pilot signal data which has a pattern corresponding to said object optical channel, and a second optical communication apparatus which receives said optical channels from said first optical communication apparatus, including: (b1) means for detecting said pilot signal data in the received optical channels; and (b2) means for calculating amplitude information of an optical signal of each of said optical channels based on amplitude information of a pilot signal component detected by said means for detecting said pilot signal data, and calculating a quality of the optical signal based on the amplitude information of the optical signal.