Gain spectrum equalization of all-optical gain-clamped erbium-doped fiber amplifier

We experimentally investigate the gain spectrum of erbium-doped fiber amplifiers whose gain is clamped by internal laser oscillation. The gain is ideally clamped and immune to the input signal power in the wavelength range of 17 nm. The clamped gain spectrum is equalized by a Mach-Zehnder interferometer, and we achieve the 17-nm-wide uniform gain, which is not dependent on input optical power levels.