Analytical model describing transients within a gain-clamped erbium-doped fiber amplifier

Wavelength-Division-Multiplexed (WDM) networks offer many advantages for increasing system capacity and managing traffic through wavelength-routing. However adding or dropping wavelength channels, whether through network design or partial failure, raises problems for amplifiers operating in a saturated regime due to steady-state and transient gain variations in the surviving channels. The steady-state variation of the amplifier can be minimized through such techniques as automatic gain control (AGC) [1], although relaxation oscillations from the gain-clamping laser will still result in transient effects which will increase in speed for a chain of EDFA's [2]. For the design and optimization of WDM networks it is desirable to have models which accurately predict the behavior of gain- clamped EDFA's. The steady-state response of such amplifiers is well understood from the numerical and analytical models published in references [3] and [4], Numerical models describing the transient response of gain-clamped EDFA's have also been developed [5,6]. To the best of our knowledge, no analytical model has been published which describes the transient response of a gain-clamped EDFA. This paper presents an analytical formulation to describe the transient response under input power excursions in an EDFA with gain clamping configuration. In addition, this model can also be utilized for evaluating the transient effects due to pump power variations in gain-clamped EDFA's.