Switchable and tunable erbium-doped fiber laser with the embedded Lyot filter

In this paper, a switchable and tunable erbium-doped fiber laser (EDFL) using an embedded Lyot filter is tested. The embedded Lyot filter based on a polarization-maintaining fiber (PMF) is theoretically analyzed and experimentally verified. By adjusting three polarization controllers (PCs), the output wavelengths in different wavelength states are emitted. By adjusting PC 1 , the output wavelengths can be switched among the single-wavelength output state and four different multi-wavelength output states, which are dual-, triple-, quad- and quintuple-wavelength outputs. In addition, the side-mode suppression ratio (SMSR) in this study can be up to ~ 53 dB. By adjusting PC 2 and PC 3 simultaneously, the output wavelengths show good tunability, and when in triple or quad-wavelength state, the wavelength interval is tunable.