Utilizations of two-stage erbium amplifier and saturable-absorber filter for tunable and stable power-equalized fiber laser.

We propose and investigate experimentally a tunable and stable fiber laser with single-longitudinal-mode (SLM) and power-equalized output based on a two-stage erbium amplifier and a saturable-absorber filter. Two-stage amplifier consists of an erbium-doped waveguide amplifier (EDWA) and erbium-doped fiber amplifier (EDFA) to generate a flatter amplified spontaneous emission (ASE) source for constant output. Saturable-absorber filter constructs by an unpumped EDF and a fiber reflected mirror (FRM) to provide a fine mode restriction and guarantee a SLM operation.