Multi-wavelength tunable ring cavity fiber laser incorporated with a Mach–Zehnder interferometer filter based on waist-enlarged fiber bitapers

Abstract

In this study, a multi-wavelength tunable ring cavity erbium-doped fiber laser based on an all-fiber Mach–Zehnder interferometer (MZI) is proposed and demonstrated experimentally. For the proposed fiber laser, the MZI is composed of two waist-enlarged fiber bitapers, and the free spectral range is 10.8 nm. In the experiment, the length of the gain medium erbium-doped fiber is 4 m, the laser threshold is 40 mW, and a 1556.8 nm single-wavelength laser is generated. When the pump power is 200 mW, the single-wavelength tunable laser can be tuned within the range of 1554.4–1563.5 nm by adjusting the polarization controller (PC). In addition, the wavelength spacing is less than 1.2 nm, the peak power difference is less than 1.1 dB, and the 3 dB linewidth is 0.04 nm. For the proposed fiber laser, four types of dual-wavelength lasing outputs are generated by adjusting the polarization controller, and the wavelength intervals are changed from 0.9 to 8.1 nm. The single-, dual- and triple-wavelength laser power fluctuations are less than 0.15, 0.37, and 0.53 dB, respectively, over a 20 min monitoring period.