Analysis Of The Effect Of Fast And Slow Light On The Sensitivity Of Optical Fiber Interferometric Sensing

The group velocity of light transmission in the medium is effectively regulated,which is the phenomenon of fast and slow light.Fast and slow light can strengthen the interaction between light and matter,it has a good application prospect in the fields of all-optical delay line,enhancement of nonlinear effects and high-sensitivity sensing.There are many ways to achieve fast and slow light.Controlling the group velocity of light in the optical fiber has attracted widespread attention due to its advantages of room temperature control and good compatibility with existing optical fiber system.This paper studies the generation technology of fiber stimulated Brillouin scattering(SBS)slow light,fast and slow light in double Lorentz-fiber Bragg grating(DL-FBG),and their sensing applications.The details are as follows:1.A new scheme for enhancing the sensitivity of sensors by introducing SBS slow light into all-fiber sensing was proposed and experimentally demonstrated.Stokes light was generated by the Brillouin laser oscillation cavity,and the Stokes light located in the gain spectrum produces a slow light effect under the action of strong pump light.At the same time,the Brillouin laser was also placed in a vibration environment as a sensing element,and the frequency change was interrogated by the Mach-Zehnder(M-Z)interferometer.Experiment showed that the sensitivity of the sensor would be enhanced by introducing Brillouin slow light into sensor.This scheme has several advantages,namely,working at any wavelength and adjustable slow light delay.In addition,the sensor sensitivity would be further enhanced by using highly non-linear fiber to optimize the scheme.2.The effect of DL-FBG fast and slow light on the sensitivity of fiber optic sensor was studied.In the experiment,we achieved it from slow light to fast light propagation in the DL-FBG by changing the wavelength of the input light.The maximum delay of the observed light pulse is 180ps(slow light)and the maximum advancement is 90ps(fast light).In addition,the center wavelength of DL-FBG will drift under the action of external strain,which were then interrogated using the M-Z interferometer.Experiment showed that the fiber sensor sensitivity obtained enhancement by introducing slow light,while the sensitivity offiber sensor decreased when combining with the fast light.Combining the experimental results and further theoretical analysis,it can be concluded that the fast light and the slow light were in the two arms of the interferometer,higher sensitivity sensing can be achieved under the same delay conditions.These experiments and analysis may provide guidance for the application of fast and slow light technology in interferometric sensors.Experimental results show that the interferometric optical fiber sensor based on fast and slow optical fiber proposed in this paper has the advantages of easy fabrication,low cost,compact structure,easy packaging and good compatibility with optical fiber system.It has good application prospect in the field of high-sensitivity optical fiber sensor measurement such as strain,temperature and vibration.