Bidirectional Reciprocal Single-Longitudinal-Mode Erbium-Doped Fiber Ring Laser Based on Hybrid Linear and Circular Polarizations

With a pair of circularly polarized lights in the Er-doped fiber, and linearly polarized lights in the rest part of the ring, a bidirectional reciprocal single-longitudinal-mode Er-doped fiber ring laser was demonstrated. The dependence of output power on pumped power of the bidirectional laser was measured. The threshold pumped power was about 7.5 mW. Then the optical spectra for bidirectional outputs were measured at a pumped power of 33.1 mW. Finally, the bidirectional single-longitudinal-mode operation was confirmed by a PZT based scanning fiber ring.