Precise and rapid wavelength-switching of fibre laser using semiconductor optical amplifier

A simple fibre laser scheme for fast and accurate wavelength switching is demonstrated, with a semiconductor optical amplifier being used as the gain medium. The laser cavity is composed of a Fabry-Perot semiconductor filter (FPSF) and a set of narrowband fibre Bragg gratings (FBGs), which determine the wavelength references. The FPSF can be tuned by changing its injection current to select a particular wavelength from those of the FBGs, and a wide tuning range can be achieved based on the Vernier effect. During switching between two discrete wavelengths, a build-up time as short as several microseconds was obtained. Furthermore, because of the short upper-state lifetime of a semiconductor amplifier, relaxation oscillations caused by wavelength switching were eliminated