| 摘要 |
An optical telecommunication system comprising means (37, 38, 39, 40) for generating optical signals of different wavelengths, an optical-fibre line with amplifying means (45, 45', 45'', 45'''), a pre-amplifier (47), and receiving means (54, 55, 56, 57), wherein the pre-amplifier (47) comprises an optical waveguide (5,7,9) doped with a rare earth material, differential-attenuation means (8) located at a first position along the doped waveguide and capable of causing an attenuation in the signal band which is greater than the attenuation caused at the pumping wavelength, and filtering means (6) located at a second position and adapted to attenuate by a value higher than a predetermined minimum, the spontaneous emission in a wavelength band contiguous with the signal band. The position and attenuation of the differential-attenuation means and filtering means and the wavelength band are selected in a functional relation with respect to each other in order to limit the output power variations from the pre-amplifier. <MATH> |
