Optical telecommunications system for wavelength division multiplexing transmissions - selects position and attenuation of differential attenuator, filter and wavelength band in functional relationship w.r.t. each other to limit output power variations from preamplifier

摘要

The system generates optical signals of different wavelengths (37 to 40), and includes an optical fibre-line with amplifier (45), a preamplifier (47) and a receiver (54 to 57). The preamplifier includes an optical waveguide (5, 7 and 9) doped with a rare earth material. A differential attenuator (8) is located along the waveguide and attenuates in the signal band greater than at the pumping wavelength. A filter (6) is located on the waveguide at a second position and attenuates by a value higher than a preset minimum, the spontaneous emission in a wavelength band contiguous with the signal band. The position and attenuation of the differential attenuator, filter and wavelength band are selected in a functional relationship w.r.t. each other to limit the output power variations from the preamplifier.