Optimum design for a single-frequency Er³⁺-doped fiber laser with external cavity feedback

A linear cavity single-frequency erbium doped fiber laser, in which a fiber Bragg grating (FBG) provides external feedback, was numerical modeled. Robust and no mode hopping single-frequency operation in this laser can be achieved. Furthermore, the longer the external cavity length is, the narrower the linewidth of the laser. The single-frequency working space of the laser has also been achieved. In order to obtain higher output power of single-frequency signal and maximally utilize the surplus pump energy, a section of 3.3 m Er³⁺-doped fiber was added to the output end. The output power is 0.373 mW that is increased by 7 dB than that without amplification. The slope efficiency is about 0.75 %.