Patent ID: 8249455

Claim:
An optical line termination device to be connected to a plurality of optical network units through optical fibers and an optical splitter, the optical line termination device comprising: a first optical transmitter transmitting an optical signal of a first wavelength to the plurality of optical network units; second optical transmitters transmitting optical signals of second wavelengths to the plurality of optical network units, the second wavelengths being other than the first wavelength and being different from each other; a first optical receiver receiving an optical signal of a third wavelength from the plurality of optical network units; second optical receivers receiving optical signals of fourth wavelengths from the plurality of optical network units, the fourth wavelengths being other than the third wavelength and being different from each other; and a control unit transmitting a request signal for requesting a response from the plurality of optical network units, wherein for each of the plurality of optical network units, time periods are measured from a transmission of the request signal to a reception of response signals transmitted from the plurality of optical network units in response to the request signal using the first optical transmitter and the first optical receiver, and wherein the plurality of optical network units are communicated with using the second optical transmitters and the second optical receivers after measuring the time periods, while adjusting transmission timings for transmitting the optical signals from the optical network units using measured time periods so as to avoid a collision of the optical signals which are transmitted from the plurality of optical network units.