Patent ID: 8886036

Claim:
An optical line terminal for monitoring and controlling upstream and downstream optical signals, comprising: an optical transmitting unit configured to generate and wavelength-multiplex a downstream wavelength division multiplexing optical signal coupled with a second low frequency monitoring signal for monitoring a downstream optical signal; a wavelength-band dividing and coupling unit configured to transmit the wavelength-multiplexed downstream wavelength division multiplexing optical signal through an optical line and transmit an upstream wavelength division multiplexing optical signal received from an optical network unit; an optical receiving unit configured to wavelength-demultiplex and receive the upstream wavelength division multiplexing optical signal transmitted from the wavelength-band dividing and coupling unit; a monitoring tap coupler configured to branch a part of optical power of the upstream and downstream wavelength division multiplexing optical signals; a monitoring signal processing unit configured to transmit the branched upstream and downstream wavelength division multiplexing optical signals to photodetectors connected with each channel by monitoring circular wavelength demultiplexing so as to be converted into electrical monitoring signals and pass the converted monitoring signals through first and second low frequency band filters to detect first and second low frequency monitoring signals; a signal processing module configured to control the downstream wavelength division multiplexing optical signal based on the detected second low frequency signal and generate optical network unit control information from the extracted first low frequency monitoring signal; and a switch configured to transmit the extracted optical network unit control information to the optical transmitting unit through the signal processing module so as to control the optical network unit.