Single-longitudinal-mode operation of a grating-based fiber-ring laser using self-injection feedback

A fiber Bragg grating- (FBG-) based fiber-ring laser that utilizes the tran smitted light; of the FBG as self-injection feedback for single-longitudina l-mode (SLM) oscillation is proposed and demonstrated. This laser is simply constructed by means of feeding back the transmitted light of the FBG and is coupled into the main ring cavity through an optical coupler. The self-i njection feedback is the key to ensuring SLM laser oscillation. The SLM ope ration principle is discussed in detail, and a SLM laser with output power of 6.6 dBm, an optical signal-to-noise ratio of 57 dB at 1549.19 nn, and a short-term linewidth of 3.5 kHz is reported. (C) 2000 Optical Society of Am erica.