Self-mixing interference in dual-wavelength fiber ring laser using cascaded fiber Bragg gratings

Self-mixing interference in dual-wavelength fiber ring laser (FRL) with serial connection of fiber Bragg gratings (FBGs) is presented. Wavelength division multiplexing and active sensing is achieved by extracting single wavelength and adding feedback to the system. The expression of the optical output power of dual-wavelength fiber ring laser is analyzed when optical feedback is introduced. The gain competition and the intensities alternation among the applied channels are discussed. We apply the developed system for displacement measurements of two moving objects and investigate the influence on output signals under different feedback conditions. The experimental results show that this system has improved efficiency to expand the channels and maintains many advantages of self-mixing interference, validating the feasibility for implementation in a dual-channel displacement sensor at the same time.