Tunable and Switchable Low-Threshold Multi-Wavelength Erbium-Doped Fiber Pulsed Laser Based on Lyot Filter and NOLM

We experimentally demonstrate a tunable and switchable low-threshold multi-wavelength erbiumdoped fiber pulsed laser. It is based on a composite structure of Lyot filter and nonlinear optical loop mirror. At a threshold of 30 mW, single-wavelength and dual-wavelength states can be obtained with a tuning range of 5 nm for the single wavelength and 1 nm for the dual wavelength. By adjusting the pump power and polarization controllers, the laser can achieve at most eightuple-wavelength operation. We use the nonlinear optical loop mirror as a saturable absorber to realize stable pulse output. The pulse sequences begin to appear when the pump power is 100 mW. The pulse repetition rate corresponding to the dual-wavelength is 40.52 kHz, and the pulse width is 144 ns. Due to its abundant range of wavelengths and significant pulse phenomenon, the proposed laser is widely used in fiber sensing and other fields.