Switchable Dual-Wavelength SLM Fiber Laser Using Asymmetric PMFBG Fabry–Perot Cavities

A ring cavity erbium-doped fiber laser based on asymmetric structure filter with two polarization-maintaining fiber Bragg grating (PMFBG) Fabry-Perot cavities is proposed and demonstrated for switchable dual-wavelength single-polarization single-longitudinal-mode (SLM) operation. The asymmetric structure filter consists of three FBGs written in a photosensitive PM fiber to form asymmetric two Fabry-Perot cavities with different cavity lengths, which can effectively decrease the transmission passband bandwidth of the asymmetric structure filter and restrain the secondary resonance peak. The fluctuations of each operating wavelength and output power of the proposed fiber laser in single-wavelength operation are less than 1 pm and 0.1 dB. The stable single polarization SLM operation is guaranteed by the asymmetric structure filter with two PMFBG Fabry-Perot cavities and the uniform PMFBG. Meanwhile, the Lorentz fitting with a 3-dB linewidth of the fiber laser for each wavelength is <;5 kHz.