Channel addition/removal response in cascades of strongly inverted erbium-doped fiber amplifiers

Signal power steady-state and transient fluctuations due to gain cross saturation in erbium-doped fiber amplifiers (EDFA's) in multiwavelength optical networks caused by addition or removal of channels due to network reconfigurations or line failures must be minimized to avoid error bursts in the surviving channels. The effects of addition and/or dropping of wavelength channels in a multiwavelength network comprising six concatenated strongly inverted two-stage EDFA's have been analyzed by numerical simulation. 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. Power excursions caused in an eight channel wavelength division multiplexing (WDM) network by the loss/addition of one, three, or six channels will be lower than 0.6 dB if the length average normalized population density of the metastable level does not drop below 0.76. No additional measures need to be taken to limit the power excursions of the surviving channels.