A C-band widely tunable and switchable erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter

Abstract In this paper, a new type of widely tunable and switchable multi-wavelength erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter is proposed. The nonlinear polarization rotation effect is obtained by adjusting two polarization controllers (PCs). The polarization-dependent isolator and the Sagnac-like loop are used as the basic structure to realize the wide tuning and wavelength switching in C-band. Compared with the traditional Lyot filter, the Sagnac-like loop is used to replace the segment of polarization-maintaining fiber, and a more uniform comb spectrum can be obtained by this filter. The tunable and switchable wavelengths can be achieved by adjusting the PCs based on the nonlinear effect of the loop. The laser can emit single-, dual-, triple-, quad- and quintuple-wavelengths. The optical signal-to-noise ratios all exceed 43 dB. It can also be adjusted to partial wavelength intervals for quad-wavelength and quintuple-wavelength. The tuning range can reach the full range of the C-band, and the laser efficiency can reach the practical application standard. It can be applied to some precision instruments and equipment.