Tunable multiwavelength erbium-doped fiber laser with a polarization-maintaining photonic crystal fiber Sagnac loop filter

We propose and demonstrate a tunable multiwavelength erbium-doped fiber laser based on a polarization-maintaining photonic crystal fiber (PM-PCF) Sagnac loop filter. Stable, room-temperature operation is obtained by employing a nonlinear optical loop mirror. At a central wavelength of 1563.000 nm, we generate 60 wavelengths within 3-dB bandwidth. The measured power fluctuation for each lasing wavelength is less than 0.2 dB in half an hour. Furthermore, by adjusting the polarization controllers in the Sagnac filter, wavelength locations of the laser lines with a fixed channel spacing of ~ 0.078 nm can be continuously shifted.