All-Optical Gain Clamped Double-Pass L-Band EDFA Based on Partial Reflection of ASE

Abstract

A new gain clamping scheme in double-pass L-band erbium-doped fiber amplifier (EDFA) based on partial reflection of amplified spontaneous emission (ASE) into the EDFA is demonstrated using a narrowband fiber Bragg grating as an ASE reflector. The proposed amplifier achieves a good gain clamping characteristic up to -12dBm of input signal power with gain variation of less than 0.5dB from a clamped gain of 22.0dB. The noise figure within the gain-clamping region is maintained below 5.0dB. The low noise figure is achieved since the proposed amplifier is not based on lasing mechanism. The proposed amplifier is also expected to be free from the relaxation oscillation problem.