Wavelength switching and tuning of fiber lasers by using a modifiable intra-cavity filter based on a modal Michelson interferometer

An experimental study of the switching and tuning of optical fiber ring lasers is presented. The laser wavelength switching and tuning are based on the modifiable wavelength dependent losses of a modal Michelson interferometer, which is composed by a bi-conical fiber taper spliced with a single-mode fiber piece. The wavelength dependent losses of the interferometer are inserted in a ring cavity laser to allow wavelength selection of laser wavelength peaks which induce preferences to generate laser emissions. By altering the interferometer geometrical dimensions, such as the single mode fiber piece length, and the curvature of the interferometer structure, the cavity losses can be adjusted to control the number of output laser wavelength peaks and also to cause wavelength shift of the output laser peaks, respectively. A maxim number of wavelength peaks of 13, and a maximum wavelength tuning by displacement-curvature of  ∼2.3 nm mm⁻¹ were obtained with maximum OSNR values of around 50 dBm. (paper)