Patent ID: 7319818

Claim:
A wavelength-division-multiplexed passive optical network (WDM PON) comprising: a central office configured to transmit a multiplexed downstream optical signal; and a plurality of subscriber devices coupled to the central office via a feeder fiber, wherein the central office comprises: a plurality of downstream optical transmitters configured to output downstream optical signals having wavelengths according to downstream injection lights; a wavelength division multiplexer including a plurality of de-multiplexing ports linked to the plurality of the downstream optical transmitters, and a multiplexing port linked to the feeder fiber, the wavelength division multiplexer configured to perform wavelength division multiplexing the downstream optical signals and wavelength division de-multiplexing a downstream band light into the downstream injection light; at least one optical switch interposed between the downstream optical transmitters and the de-multiplexing ports and configured to input a downstream band light output from a selected downstream optical transmitter to the multiplexing port and for inputting a downstream optical signal output from a remaining downstream optical transmitter, which is not selected, to the de-multiplexing port; and wherein the optical switch has a first port to a third port for switching the downstream optical transmitters between the de-multiplexing ports and a first optical coupler.