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Abstract

A method and apparatus for dynamically obtaining a substantially linear gain tilting of the output spectrum of an EDFA, in either automatic gain control or automatic power control modes. A necessary tilt is obtained while holding the total gain or total output power of the EDFA constant. The apparatus includes a variable mid-stage attenuator inserted between two (first and second) gain sections of the EDFA. The tilting is performed by ordering the attenuator to increase or decrease its attenuation in a value proportional to the tilting needed, while changing substantially simultaneously the pumping of the second gain section. The attenuation change process is based on the saturation mechanism of the erbium amplifier in the L-band, which translates the wavelength-independent loss of a variable optical attenuator into a linear wavelength-dependent gain at the EDFA output. The attenuation and pumping changes are preferably performed according to tables and functions contained in a management unit connected to the EDFA.

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