Tunable gain-clamped double-pass Erbium-doped fiber amplifier.

A tunable, gain-clamped (GC) double-pass Erbium-doped fiber amplifier (EDFA) with a linear laser-cavity configuration has been demonstrated. It solves the problems existing in the conventional linear-cavity GC-EDFA based on two fiber Bragg gratings (FBGs), in which the clamped-gain is very difficult to be tuned. In the new GC-EDFA, the lasing oscillation for clamping the gain is produced in a linear cavity comprised by a FBG and a fiber reflection mirror (FRM). Between them, a filter filters out the lasing light, and then a variable optical attenuator changes the loss of the laser cavity for tuning the clamped-gain. Meanwhile, the double-pass configuration is used to enhance the gain efficiency, and therefore the level of the clamped-gain is greatly improved.