Patent ID: 7526199

Claim:
An optical transmission system, comprising: a first optical transmission apparatus for receiving a first wavelength-division multiplexing light as first optical signals of different wavelengths from a first optical transmission line and for transmitting a part of the first optical signals of different wavelengths contained in the first wavelength-division multiplexing light to a second optical transmission apparatus, and for receiving second optical signals of different wavelengths and for multiplexing the second optical signals for transmission to a second optical transmission line; and the second optical transmission apparatus for receiving one of the first optical signals of different wavelengths from the first optical transmission apparatus and for transmitting one of the second optical signals to the first optical transmission apparatus; wherein the second optical transmission apparatus monitors a power level of the one of the second optical signals and sends a result of the monitoring to the first optical transmission apparatus: wherein the first optical transmission apparatus intercepts the one of the second optical signals transmitted from the second optical transmission apparatus in dependence upon the result of monitoring; wherein the second optical transmission apparatus comprises: an input check unit for monitoring a power level of a signal from the second optical transmission apparatus and providing an output indicative thereof; and wherein the first optical transmission apparatus comprises: a demultiplexer for separating the first wavelength-division multiplexing light received from the first optical transmission line into first optical signals of different wavelengths to transmit one of the first optical signals to the second optical transmission apparatus; a multiplexer for multiplexing signals of different wavelengths received from the outside including the second optical transmission apparatus to transmit multiplexed signals to the second optical transmission line; and an output adjuster for intercepting a signal from the second optical transmission apparatus so as to inhibit receipt of the signal from the second transmission apparatus by the multiplexer depending on the output of the input check unit.