1.6 µm tunable and switchable single-frequency erbium-doped fiber laser

We present a tunable and switchable single-frequency (SF) erbium-doped fiber laser (EDFL) operating at 1.6 µm. For the first time, a multichannel Sagnac filter, a "θ" sub cavity, and a saturable absorber (SA) have been combined to achieve SF operation of single- and dual-wavelength tunability as well as single-dual-triple-wavelength switching. The laser exhibited excellent stability, with no mode-hopping over the 60-minute observation period. Furthermore, linewidths measured utilizing the short-delay self-heterodyne interferometry method are less than 300 Hz. The investigated narrow linewidth SF EDFL has the potential to extend the applications in optical communications and provide a new idea for L-band tunable lasers.