Tunable dual-wavelength thulium-doped fiber laser by employing a HB-FBG

A novel tunable dual-wavelength thulium-doped fiber laser is demonstrated experimentally. The wavelength-tuning by employing a high birefringence fiber Bragg grating is proposed in 2- μm band lasing for the first time. By adjusting the polarization controller, stable dual-wavelength operation at the wavelengths of 1941.40 and 1942.21 nm is obtained. The optical signal-to-noise ratio is better than 48 dB. A 15.5% slope efficiency is achieved using a 90% output coupling ratio for laser extracting. The wavelength-tuning range in dual-wavelength operation is as wide as 6.93 nm.