Optically tunable multiwavelength fiber laser based on a Mach–Zehnder comb filter incorporating ytterbium-doped fibers

A tunable multiwavelength fiber laser based on an optically tunable Mach–Zehnder comb filter incorporating Yb-doped fibers is proposed and demonstrated. By selectively pumping the Yb-doped fibers, the lasing lines can be continuously tuned towards longer or shorter wavelengths. Up to 20 stable lasing lines with channel spacings of 0.76 nm in a 3-dB bandwidth were achieved at room temperature. Moreover, the laser tuning operation could easily cover the whole channel spacing by simply shifting the half-channel spacing separately in two opposite directions. The proposed multiwavelength fiber laser provides a simple and flexible optical tuning operation, which would be beneficial for its applications in fields requiring accurate tuning optical sources.