Performance of a practical gain controlling approach for erbium-doped fiber amplifier

Abstract

Wavelength routing and reconfigurable cross connects are emerging concepts for optical multiwavelength telecommunication networks. They provide more efficient usage of the network resources, as individual wavelength channels can be added or dropped from the wavelength multiplex. However, problems arise with the erbium-doped fiber amplifiers (EDFAs), whose gain is dependent on the input power level. If the gain of the EDFA is not by some means controlled, transient effects will occur due to the EDFA's slow gain dynamics. In this paper a simple device for controlling the gain of the EDFA is studied. The gain- controlling scheme is based on a fast pump laser control. Part of the total input power to the amplifier is detected by the gain controlling circuitry, which then compensates for the changing gain by adjusting the pump laser power. In the study, transient effects due to changing number of channels in an EDFA are measured. The response time and the transient suppression of the gain-controlling device are verified through measurements. The effect of the amplifier gain tilt is also studied. A comparison against other proposed gain-controlling schemes is done.