Gain-clamped fiber amplifier with a loop mirror configuration

A new configuration of a gain-clamped fiber amplifier is proposed and demonstrated. A laser cavity was formed by a fiber grating and a loop-mirror containing an erbium-doped fiber amplifier in its loop. Owing to the loop-mirror property, the signal light does not enter the laser cavity, and the signal light around the oscillation wavelength can be amplified in the same way as signals far from the oscillation wavelength. Our configuration also has an advantage that only the signal light appears at the output port.