Patent ID: 7613396

Claim:
An optical multiplexing communication system for transmitting information by multiplexing a plurality of communication channels on an optical transmission medium, wherein the plurality of communication channels include a first channel of a relatively small optical power state and a second channel of a relatively large optical power state, comprising: a multiplexer for multiplexing the plurality of channels on the optical transmission medium; and a demultiplexer for demultiplexing multiplexed communication channels that have traveled through the optical transmission medium, to separate out at least the first channel from the multiplexed communication channels, wherein: a second-channel transmission characteristic of the multiplexer for the second channel, a first-channel transmission characteristic of the demultiplexer for the first channel, and an optical power of the second channel are set so that the second channel does not affect the first channel, the second-channel transmission characteristic of the multiplexer comprises a first isolation from the first channel, wherein the first isolation is set such that crosstalk light due to spontaneous emission light of a light source for the second channel is suppressed to become smaller than optical power of signal light on the first channel, the first-channel transmission characteristic of the demultiplexer comprises a second isolation from the second channel and a transmission bandwidth for the first channel, wherein the second isolation is set such that crosstalk light due to nonlinear optical effects caused by propagation through the optical transmission medium is suppressed to become smaller than optical power of signal light on the first channel and the transmission bandwidth is set to a bandwidth not greater than a predetermined value within such a range that optical power of the crosstalk light due to nonlinear optical effects does not affect a spectrum of the first channel, and the demultiplexer comprises: a first separator for separating out a first optical signal on at least the first channel from the multiplexed communication channels according to a first transmission characteristic; and a second separator for separating out a second optical signal on the first channel from the first optical signal according to a second transmission characteristic, wherein the first transmission characteristic provides the second isolation from the second channel and the second transmission characteristic provides the transmission bandwidth.