Single-longitudinal-mode linear-cavity fiber laser using subring cavities and broadband fiber mirror

A single longitudinal mode selection is realized in a linear-cavity fiber laser constructed by using a broadband fiber mirror and a partial reflectance fiber Bragg grating as the cavity ends. At 1550.87 nm wavelength, the measured signal-to-noise-ratio is 60.48 dB. The narrow linewidth of less than 1MHz is obtained using multiple subring cavities as mode filters. The pumping efficiency is 16% improved by recycling the residual pump power to gain medium.