Patent ID: 7848652

Claim:
A wavelength division multiplexing passive optical network system comprising a central office, a remote node, and an optical network unit, characterized in that the central office generating a multi-mode light having a mode interval equal to a period interval of a multiplexing filter of the remote node, the multi-mode light being used to control a wavelength of an uplink transmission optical signal of the optical network unit, and the central office amplifying the multi-mode light to be self-injected by using a fixed-gain optical amplifier without an isolator, the central office to transmit the multi-mode light and a downlink transmission optical signal to the optical network unit; the remote node demultiplexing the multi-mode light with the multiplexing filter to transmit the demultiplexed multi-mode light to the optical network unit and multiplexing the uplink transmission optical signal to transmit the multiplexed uplink transmission optical signal to the central office; the optical network unit generating the uplink transmission optical signal by modulating a data signal with a Fabry-Perot laser, the Fabry-Perot laser using the multiplexed multi-mode light as an injection optical source; and an amplification unit amplifying the multi-mode light to obtain constant gains in the modes of the multi-mode light by using a fixed-gain semiconductor optical amplifier without an isolator and sending the amplified multi-mode light as a feedback to the Fabry-Perot laser; wherein the central office further comprises a light generation unit and a filter unit flattening outputs of the modes of the multi-mode light by using a flattening filter provided between the light generation unit and the amplification unit.