All-Optical Gain-Clamped Erbium-Doped Fiber Amplifier With Improved Noise Figure and Freedom From Relaxation Oscillation

Abstract

All-optical gain clamping scheme of erbium-doped fiber amplifier (EDFA) based on partial reflection of amplified spontaneous emission (ASE) into the EDFA is proposed and successfully demonstrated by using a coarse wavelength division multiplexing coupler with a mirror as an ASE reflector. The proposed gain-clamped EDFA (GC-EDFA) has good gain clamping characteristics up to -12 dBm of input signal power with 1-dB gain reduction from a clamped gain of 21 dB. Thanks to noncavity structure of the proposed GC-EDFA the amplifier is free from relaxation oscillation and has 1-dB improved noise figure, compared to a previous GC-EDFA based on a ring-type optical cavity.