Tunable dual-wavelength ring fiber laser with stable output based on saturable absorber and thin core passive fiber

• A dual-wavelength ring fiber laser with stable output is proposed.
• EDF was used as a saturable absorber to improve the stability of output laser.
• Thin core passive fiber was used in the ring cavity as a Mach–Zehnder filter to improve laser stability.
• A dual wavelength or single wavelength laser can be produced by adjusting the VA.

A dual-wavelength erbium-doped ring fiber laser is proposed and experimentally demonstrated though a detailed theoretical analysis and experimental verification. The proposed dual-wavelength erbium-doped fiber (EDF) laser, which is based on a ring fiber laser structure, is fabricated using two fiber Bragg gratings. By adjusting the gains and losses of the fiber laser structure, the laser can be switched between single- and double-wavelength modes. A saturable absorber (SA) is used to improve the output laser stability, which is further enhanced by splicing a thin core passive fiber (TCPF) into the laser cavity to produce a Mach–Zehnder filter effect. Optimizing the lengths of the SA and TCPF results in the adoption of a 1-m EDF and a 4-m passive fiber. On the basis of these enhancements and optimizations, a fiber laser with stable output is constructed that incurs single- or dual-wavelength laser shifts of less than 3 pm at room temperature over a period of 250 s.