Research Of Fiber Interferometer Based On Vernier Effect

The Vernier effect can simultaneously amplify the sensitivity and dynamic range of the fiber interferometer,which is a research hotspot in the field of fiber sensing.This article will focus on the Vernier effect as the core,the main contents are as follows:(1)The theoretical model of the Vernier effect is introduced.The spectral characteristics of the cascaded Vernier effect and the parallel Vernier effect are theoretically analyzed.The amplification effect of the Vernier effect on the sensitivity and dynamic range of the interferometer is mathematically demonstrated.This work provides a theoretical basis for further research.(2)A Sagnac interferometer based on cascaded polarization maintaining fiber(PMF)is proposed.The Jones matrix is introduced to analyze the transmission characteristics of the interferometer.Its ability to generate Vernier effect is theoretically demonstrated.The spectrum of the interferometer consists of an envelope and a finesse spectrum.It is proposed that using a single PMF to measure the strain,and using two PMF to measure the temperature.This meathod constructs a difference between the envelope and the fine spectrum sensitivities for strain and temperature sensing.Simultaneous measurement of two parameters is achieved with the cross matrix.The strain sensitivities of the envelope and the finesse spectrum were 58.0 pm/?? and 5.9 pm/??,respectively,and the temperature sensitivities were-1.05 nm/°C and-1.36 nm/°C,respectively.(3)A 2 ?m tunable laser was realized using the interferometer proposed above.First,try to tune the wavelength by applying strain to a single PMF.The simulation shows that the wavelength obtained by this method is step-wise and cannot be continuously changed.It is proposed to simultaneously apply strain on the two PMF so that the interferometer can be tuned continuously.Finally,a 2 ?m tunable fiber laser with a tuning range of over 40 nm was obtained.(4)The traditional demodulation method of the Vernier effect is the envelope fitting method.The regularity of the interferometer spectrum is very high.If there are other frequency components in the spectrum,it is difficult to distinguish the envelope.Aiming at a shortcoming,a demodulation method based on spectrum analysis is proposed,and the demodulation ability of this method is verified by experiments.