Research On Conical Micro Fiber Sensor Based On Functional Fiber Surface

With the wide application of Internet of Things in social life,industrial production relies more and more on the high-speed transmission of information and on real-time processing.In the social life,people have put forward higher requirements for the new optoelectronic devices.High integrated and performance optical fiber photonic devices have become a new favorite in the field of optoelectronics.Among them,the optical fiber photonic devices based on tapered optical fiber have attracted unprecedented attention as the basic structural unit and have great potential applications in many fields.Research at home and abroad actively carry out related research work.The strong evanescent field is around the conical micro optical fiber,using it as a basic sensing unit and interacts with the surrounding environment,and realizes the sensor for detecting the external environmental parameters.Compare to ordinary optical fiber sensors,the tapered fiber sensor has several advantages such as,compact structure,fast response and high sensitivity.In this paper,the interaction between the conical structure and the external parameters is strengthened through the nano functional materials,thus the sensitivity of the sensor is further improved.In this,the sensing structure is mainly prepared by arc discharge and fused tapered cone method.The microstructure design of optical fiber with different conduction characteristics is made by different preparation methods.At the same time,the characteristics of the conical sensing structure are further enhanced with the combination of nanoscale functional materials.The effect of nano functional material on the spectral transmission is studied,and the theoretical analysis is carried out through numerical simulation and the theory is further demonstrated by the experiment.The main content of this thesis includes:1.The conical microstructural fiber is prepared by the hydrogen oxygen flame melting method.The tapered micro-fibers with different parameters were prepared by controlling the size of the hydrogen-oxygen flame,the swinging frequency and duration of the flame.The binding force of optical fiber to light is closely related to the diameter of the fiber.With the weakening of optical fiber's binding force to the beam,the light energy which is bound in the core is leaked into the cladding,thus forming evanescent waves.The weaker the beam binding force of the fiber is,the stronger the energy of the evanescent field,the interaction with the outside world,and the more sensitive feedback to the external parameters.2.A magnetic field and refractive index sensor based on a small mode S-shaped micro fiber is designed.The surface morphology of the less mode fiber is mutated by arc discharge.Due to the change of the axial structure of the optical fiber,the optical transmission produces axial asymmetry,which stimulates the high-order cladding mode,and forms the sensors which interfere each other between the cladding mode and the core mode.3.A kind of hybrid magnetic field sensor based on asymmetric cone micro-fiber is proposed.The sensor structure is prepared by different conical drawing methods.The mode of transmission in optical fiber is numerically calculated,and the modes in interference are determined,and the mode transmission characteristics are studied in theory.In the experiment,the evanescent field effect is effectively increased by combining with the nano magnetic fluid.According to the wavelength shift of the peak with the change of the external magnetic field,the high sensitivity detection of the magnetic field is realized,and the sensitivity is0.302nm/Oe.4.The single layer MoS₂ is coated on the surface of the single mode S-shaped micro optical fiber structure,and the sensor are prepared to realize the relative humidity sensor.The mode coupling and interference characteristics of the fiber are theoretically analyzed by numerical calculation.The wavelength of the interference peak of the relative humidity sensor and the variation of the amplitude with the humidity are analyzed.The humidity sensitivity can reach-0.148dB/RH.