Comb Spectrum Shaping Effect of a Fiber Sagnac Loop on an All-Normal-Dispersion Yb-Doped Mode-Locked Fiber Laser

In this letter, a high birefringence fiber (HBF) Sagnac loop is adopted in an all-normal-dispersion (ANDi) Ytterbium-doped (Yb-doped) passively mode-locked fiber laser. The HBF Sagnac loop acting as a comb spectrum filter has properties of controllable wavelength spacing and tunable transmission wavelength in the laser. With these properties of the HBF Sagnac loop filter, the laser offers a wide range of lasing performance. In the experiment, by changing the HBF length and adjusting the polarization within the loop, obviously different spectral profiles are observed, and broad wavelength tunability is also achieved.