Tunable and stable multi-wavelength erbium-doped fiber laser based on a double Sagnac comb filter with polarization-maintaining fibers

In this paper, a tunable and stable multi-wavelength erbium-doped fiber laser that employs a double polarization-maintaining Sagnac loop comb filter is proposed and experimentally demonstrated. The two nested Sagnac loops are used as the comb filter, which was fabricated using two 3-dB couplers, two polarization controllers (PC), and two sections of polarization-maintaining fibers (PMFs) with lengths of 1.2 m and 1.8 m, respectively. In the proposed laser, a stable and tunable single-, double-, and triple-wavelength lasing was obtained experimentally in the spectral range of 1528–1564 nm, the side mode suppression ratio (SMSR) was higher than 38 dB, and the wavelength shifts and power fluctuations were less than 0.04 nm and 4.7 dB, respectively, for a duration of 10 min at a room temperature of 26 °C. Furthermore, the laser can emit quadruple-wavelengths through adjustment of the two PCs in the experiment.