A Stable and Tunable Linear-Polarization Fiber Ring Laser With a High SMSR by Using a Compounded Fiber Filter

A stable and tunable linear-polarization fiber ring laser with a high side-mode-suppression ratio (SMSR) is proposed and experimentally demonstrated by using a compounded fiber filter, which is composed of a dual-pass Mach-Zehnder interferometer filter incorporating one segment of polarization-maintaining fiber and a high finesse filter. By adjusting the polarization controllers, the output laser can be tuned from 1560.37 to 1568.56 nm and an SMSR as high as 72 dB is achieved. In addition, the peak power fluctuation and wavelength shift are monitored to be less than 0.08 dB and 0.02 nm over an hour. Due to the introduction of the compounded fiber filter as a wavelength selector, the side mode of lasing output can be effectively suppressed and mode competition can be weakened. As a result, the SMSR of lasing output is increased and power stability is improved.