Patent ID: 7822345

Claim:
An output stage for wavelength division multiplex (WDM) information transmission, comprising: a plurality of information channel ports each providing a carrier wave modulated with an information signal at an output of the output stage, a first filling light source for providing a filling lightwave to the same output having a power corresponding to a desired power signal supplied to a control input of the first filling light source, at least one photodetector for detecting a total power of all filling lightwaves and carrier waves at the output of the output stage, a first control circuit for generating a first desired power signal such that the total power detected by the photodetector is held constant at a predetermined reference value, the first filling light source being part of a first assembly mounted replaceably at a first mounting location of the output stage, the output stage having a second mounting location at which a second assembly comprising a second filling light source is mounted, and the output stage including an auxiliary circuit for providing one of the two filling light sources with a continuously decreasing second desired power signal, the auxiliary circuit being a second control circuit, each control circuit having a filling light source associated with it and receiving the desired power signal generated by the respective control circuit, each control circuit including means for reducing the reference value individually assigned to them, the control circuits being switchable between two different reaction speeds for controlling the power of the filling light source.