Characteristics of double fiber ring incorporated with a fiber Bragg grating

A novel slow-light reflector composed of a double ring resonator with a fiber Bragg grating (FBG) incorporated is proposed in this paper, which can be used as a mirror of narrow linewidth fiber laser. Due to the Vernier effect, it is shown that the amplitude of resonance peaks is modulated by the simulations and the mode spacing is expanded greatly. Compared with the case of single ring, the mode hopping is mitigated effectively, while the line narrowing function is maintained. The light recirculating propagation in the fiber resonator provides not only high reflectivity, but also an enlarged group delay, which shows a good slow-light property.