The transmission characteristic of the multi-polarization controlled fiber loop mirror

The multi-polarization controlled fiber loop mirrors (FLMs) are presented and their characteristics are studied, because of the non-tunable characteristic of the wavelength interval for single-polarization controlled FLM. The multi-polarization controlled FLMs are studied theoretically with the Jones matrix. We experimentally study the single-, double- and triple-polarization FLMs, and the results show that compared with the single-polarization controlled FLM, the multi-polarization controlled FLM possesses the interval tunability and the side-frequency restriction are shown. The experimental results are in good agreement with theoretical results. The side-frequency restriction characteristic is shown in a ring fiber laser of double-polarization FLM and the side-mode suppression ratio is enhanced by 5 dB compared with the one of single-polarization FLM.