Spatial-mode switchable, multi-wavelength all-fiber erbium-doped fiber (EDF) laser based on low modal crosstalk mode multiplexer/demultiplexer (MUX/DEMUX)

We experimentally demonstrate an all-fiber erbium-doped fiber ring laser based on a Sagnac interferometer with a low modal crosstalk mode multiplexer/demultiplexer (MUX/DEMUX). Three linearly polarized (LP) modes are generated by mode MUX/DEMUX, which consists of cascaded mode-selective couplers. The proposed fiber laser can simultaneously achieve spatial-mode switching and multi-wavelength tuning. In the experiment, single-, dual-, and triple-wavelength lasing outputs for LP₀₁, LP₁₁, LP₂₁ and hybrid modes are obtained. The stabilities for LP₀₁, LP₁₁, LP₂₁ and hybrid modes are investigated in more than 20 min, 16 min, 12 min and 16 min, respectively. Moreover, the mode intensity profiles, the OSNRs of the lasing output and the slope efficiencies are also measured. (paper)