Optical fiber temperature sensor based on beat frequency and Vernier effect of fiber ring resonator composite cavity

A fiber temperature sensing scheme based on beat frequency and Vernier effect of fiber ring resonator (FRR) with composite cavity is proposed and experimentally demonstrated. The optical FRR as a sensor is put into the linear cavity fiber laser, and Vernier effect is generated when the resonance spectrum of the optical FRR and the longitudinal mode of the laser are superimposed. The beat frequency envelope spectrum corresponding to the longitudinal mode Vernier spectrum is used to realize fiber ring sensing in electrical domain, and the sensing information is obtained by tracing the envelope of beat frequency signal, which has the advantages of stable system, simple structure, low cost and high sensitivity.