All-optical stabilization of cascaded multichannel erbium-doped fiber amplifiers with changing numbers of channels

While multiwavelength erbium-doped fiber amplifiers (EDFAs) are immune to bit-by-bit crosstalk because of their slow gain dynamics, changing the number of wavelength channels in an EDFA operating near saturation changes the output power in each channel. All-optical feedback can stabilize EDFA gain independent of total input power, but this technique has been applied to only a limited extent when more than one channel is present. Additionally, published reports have not addressed all-optical stabilization of amplifier chains. Even when the first amplifier is gain stabilized, the number of channels in the subsequent amplifiers changes and thus each amplifier must in turn be stabilized. We show here the output power in a given wavelength channel can be stabilized when only the first amplifier of the chain is modified. This is accomplished by generating a compensating signal in the first amplifier, using all-optical feedback, and then propagating the compensating signal along the entire chain.