Switchable multiwavelength erbium-doped fiber laser with a multimode fiber Bragg grating and photonic crystal fiber

In this letter, a simple switchable multiwavelength erbium-doped fiber laser is proposed and demonstrated. The wavelengths are determined by a multimode fiber Bragg grating which has a wavelength separation of 0.8 nm. Five-wavelength operation at room temperature can be achieved by employing a highly nonlinear photonic crystal fiber to induce four-wave mixing effect. The proposed laser can operate either in a stable five-wavelength mode or wavelength switching modes by varying the states of polarizations of the laser cavity.