Patent ID: 7917032

Claim:
A multi-bit-rate optical communication method in an optical communication system having an optical line terminal, a plurality of optical network units including a first optical network unit capable of receiving data at a first bit rate of once every M down bits and a second optical network unit capable of receiving data at a second bit rate which is said first bit rate x a first constant M down where M down is greater than 1 so that the second bit rate is thereby higher than the first bit rate, and a branching unit to branch an optical signal transmitted from the optical line terminal in a predetermined frame format to said plurality of optical network units, the method comprising: transmitting, by the optical line terminal, a first data area including frame synchronization information in said frame format at the first bit rate, and transmitting a second data area at the second bit rate; performing, by the second optical network unit, reception processing of the optical signal from the branching unit at the first bit rate to detect said frame synchronization information in the first data area in said frame format; and performing, by the second optical network unit, based on the detected frame synchronization information, reception processing of the second data area at the second bit rate in said frame format.