Miniaturized MMZI concatenated FLM for gain equalization of ASE response of an EDFA

A miniaturized micro Mach-Zehnder interferometer (MMZI) has been employed, for the first time, for gain equalization of amplified spontaneous emission spectrum of an erbium doped fiber. An all-fiber MMZI with interference length of ∼1.5 cm, free spectral range of 40 nm, extinction ratio of 8 dB, and the total length of ∼5 cm, was indigenously realized. The interferometer was concatenated inside/outside the fiber loop mirror, with a built-in polarization controller. By appropriately adjusting the retardance and orientation angle of the polarization controller, the amplified spontaneous emission response of an erbium doped fiber has been flattened over the wavelength range of 35 nm with a peak to peak difference of ±0.46 dB.