Switchable Multi-Wavelength Erbium-Doped Fiber Lasers Based on a Mach–Zehnder Interferometer Using a Twin-Core Fiber

A switchable multi-wavelength erbium-doped fiber ring laser based on a compact in-fiber Mach–Zehnder interferometer comb filter at room temperature is presented. The comb filter is formed by splicing a section of twin-core fiber between two single mode fibers. By adjusting the states of the polarization controller appropriately, the laser can be made to operate in stable single-, dual- and three-wavelength lasing states. The operation principle is based on spectral hole burning induced by the saturated effect and polarization hole burning.