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.