Multiwavelength Switchable Erbium-Doped Fiber Ring Laser With a PBS-Based Mach–Zehnder Comb Filter

We propose and demonstrate a multiwavelength switchable fiber ring laser by employing a simple but novel polarization beam splitter (PBS)-based Mach-Zehnder (M-Z) comb filter. The proposed comb filter consists of a rotatable polarizer, a PBS, and a 3-dB fiber coupler. By adjusting the polarization state of the lasing light launched into the PBS, the multiwavelength switchable operation can be easily achieved. When the proposed comb filter was incorporated into the laser cavity, up to 11 multiwavelength switchable lasing lines with a channel spacing of 1.2 nm were obtained. In addition, the lasing locations and the number of the lasing lines can be flexibly tuned by exploiting the wavelength-dependent loss mechanism.