Switchable Dual-Comb Fiber Laser Based on Sagnac Loop for Wavelength-Multiplexing and Polarization-Multiplexing

We present an all-fiber erbium-doped mode-locked laser capable of switching among continuously tunable single-pulse mode-locking, wavelength-multiplexing asynchronous-pulse mode-locking, and polarization-multiplexing asynchronous-pulse mode-locking states. The multiplexing mechanisms under different conditions are confirmed by separating the asynchronous-pulse sequences. Experimental results and numerical simulations indicate that the adjustment of the polarization controller within the Sagnac loop is the key factor for switching between wavelength- and polarization-multiplexing asynchronous-pulse mode-locking. The multiple output characteristics of the same laser can support diverse application scenarios, offering significant cost reduction in practical applications. To the best of our knowledge, this is the first demonstration of switching between wavelength- and polarization-multiplexing asynchronous-pulse mode-locking states in a noise-like laser. Compared to previous related work, the proposed laser not only enables tunable mode-locking wavelengths but also achieves higher pulse energy. This work provides a light source solution with a simple structure and high switchability for dual-comb applications.