Single-Longitudinal-Mode Dual Wavelength-Switchable Fiber Laser Based on Superposed Fiber Bragg Gratings

In this work, a simple switchable dual-wavelength short-cavity fiber laser operating in a single-longitudinal-mode regime at room temperature and based on superposed fiber Bragg gratings is proposed and experimentally demonstrated. Only by introducing stress into one of the overwritten FBGs, single- or dual-wavelength laser oscillations can be attained. Either single- or multimode operation of the laser can be easily achieved. Single-longitudinal-mode emission has been verified in two different ways: the first corroboration has been conducted by the heterodyne detection of the output signal, and the second one has been carried out by using a high-resolution optical spectrum analyzer.