Quintuple-wavelength EDF laser based on multimode fibers with different core diameters

Abstract

A switchable quintuple-wavelength erbium-doped fiber laser using the linear-cavity configuration is proposed and demonstrated experimentally at room temperature. It is composed of two Sagnac loops that act as the cavity mirrors in the resonant cavity and contain two kinds of multimode fibers with different core diameters (50 and 62.5 µm). The two loops become two comb filters to jointly excite the multi-wavelength output. By using the effects of multimode interference and polarization hole-burning, and after adjusting a polarization controller, the laser can switch flexibly to output nine different kinds of modes from single-wavelength to quintuple-wavelength. All lasing lines with a narrow linewidth of less than 0.25 nm have an optical signal-to-noise ratio of more than 14 dB. The laser has good power uniformity shows good stability with respect to the wavelength and peak power.