Fast power transients in concatenated Pr/sup 3+/-doped fluoride fiber amplifiers

Amplified multiwavelength optical communication networks are prone to substantial saturation induced power fluctuations when a channel is turned on or rerouted. This perturbs amplifier gains at other wavelengths. The effects of addition and/or dropping of wavelength channels due to network reconfigurations or line failures in a multiwavelength network comprising eight concatenated Pr/sup 3+/-doped fluoride fiber amplifiers (PDFFAs) have been studied theoretically. A large-signal numerical model which incorporates time variation effects and the downstream and upstream propagation of signal, pump and amplified spontaneous emission has been used. In an eight channel WDM network the loss of channels will cause very fast power excursions of the surviving channels. The necessary speed of the link control circuit for surviving channel protection has been investigated.