Single/Dual Wavelength Switchable Fiber Laser Based on Composite Interference Filtering

A single- and dual-wavelength switchable fiber laser based on composite interference filtering is proposed and experimentally demonstrated. By utilizing a seven-core fiber interferometer cascaded with a Sagnac loop, the linewidth of the laser output is narrowed to less than 0.02 nm, and the optical signal-to-noise ratio better than 61 dB. The laser output wavelengths can be switched between single- and dual-wavelength by adjusting the polarization controller and the pump power. The laser exhibits high stability in both wavelength and power. The proposed laser structure is simple, with high OSNR and excellent stability, making it promising for applications in optical communication, sensing, and wavelength division multiplexing systems.