Multi-wavelength thulium-doped fiber laser by using Sagnac loop mirror

A multi-wavelength thulium-doped fiber laser based on a Sagnac loop mirror is demonstrated. By increasing pump power and adjusting the state of polarization, stable laser outputs with single, double, three, four or five wavelengths are realized within the spectral range between 1954 and 1975 nm. The laser has a high side-mode suppression ratio (SMSR) of 40–50 dB.