Study On Polarization Characteristics Of Graphene Coating Optical Fiber MZI

All-fiber Mach-Zehnder interferometer(MZI)is an all-fiber interference structure.Because of its simple structure,good device integration,high sensitivity and low cost,it has attracted extensive attention of researchers in the field of optical fiber communication and optical fiber sensing.Graphene,as a new two-dimensional carbon nanomaterial,has unique optical,thermal and electrical properties due to its unique zero band gap structure.Graphene film optical fiber devices are composed of graphene and optical fibers,and novel characteristics of these devices are explored.This provides a possibility for the development of new optical fiber devices.In this paper,the single-mode fiber(SMF)-Thin-core fiber(TCF)-Single-mode(STS)fiber structure MZI is used as the basic structure.By coating graphene on TCF and using the interference principle of all-fiber MZI,the mode light field of the layer is coupled into the graphene layer and interacts with graphene.The optical information related to the graphene film is obtained by MZI interference spectrum.The MZI of graphene film was studied by theoretical and experimental methods.The main work of this paper is as follows:1.The development status of all-fiber MZI refractive index sensor at home and abroad is summarized.The sensing structure of M-Z all-fiber interferometer is classified and introduced.The research and development status of optical absorption and polarization characteristics of graphene are reviewed,and the development status of graphene film optical fiber structure is analyzed.2.All fiber MZI refractive index sensing principle and analysis to part of the cladding enhancement method.The M-Z sensor based on STS structure is theoretically analyzed and explored,and the sensitization method of partial cladding treatment is theoretically demonstrated.3.The optical power control characteristics of MZI with partially decladding graphene film were studied experimentally.The structure and preparation method of the sensor are introduced in detail.The sensitivity of the sensor under different thickness cladding is determined by optical power experiment of the sensor.The experimental results show that the sensitivity of the sensor is 14.5 pm/mw,18.7 pm/mw and 13.9 pm/mw when the power of the optical fiber is adjusted from 2 mw to 16 mw,and the STS structure is corroded for 5 minutes,10 minutes and 20 minutes respectively.Therefore,it is concluded that the sensitivity of the sensor is the highest when the power of the optical fiber is corroded for 10 minutes.4.Experimental study on MZI polarization of graphene films.Respectively to the polarization direction of 0°,45°,90° Angle of linear polarized light power control characteristics of the experimental analysis,the experimental results show that when the fiber in the power regulation from 2.2 mw to 22.7 mw,the input optical power increase with different polarization,polarization interference wavelength present a linear blue shift and unrelated nonlinear,and the sensor sensitivity are 12.2 pm/mw.5.Polarization characteristies of graphene film MZI.The polarization direction of the input light is adjusted from 0 to 180 degrees and the influence on the MZI interference spectrum is observed.The experimental results show that the interference wavelength of MZI changes periodically with the change of the polarization direction of the incident light.At the same time,the drift periods corresponding to different interference wavelengths are slightly different,which is mainly related to the polarization-dependent superposition of different cladding modes.