Fiber-based multiple-beam reflection interferometer for single-longitudinal-mode generation in fiber laser based on semiconductor optical amplifier

A technique of single-longitudinal-mode selection in a fiber laser by means of a fiber multiple-beam reflection interferometer (FRI) has been experimentally demonstrated for the first time. The laser is based on a semiconductor optical amplifier placed in a linear fiber cavity formed by a fiber Bragg grating (FBG), and the FRI generates at 1529.24 nm with output power of 1 mW in single-frequency regime with a linewidth of about 217 kHz and polarization extinction ratio of >30 dB. The FRI technique potentially enables fast tuning (within the FBG bandwidth of ∼0.9 nm in our case) by varying the base length of the FRI that can be used in a number of practical applications.