Fabrication Of Optical Fiber Sensor Based On The Electro-thermal Fused Tapering Method

Nowadays,the two main application fields of fiber grating devices are optical fiber sensor and optical fiber communication.Among them,tapered optical fiber devices play a crucial role in the field of optical fiber sensing.At present,the manufacturing methods of cone optical fiber sensor include arc discharge,hydrogen and oxygen flame heating,physical polishing,CO₂ laser ablation,chemical corrosion and so on.In this thesis,a kind of ring graphite-like resistive electrothermal fiber is used to make tapered fiber devices.The taper waist thickness,variable diameter distance,flattened zone length and so on are controlled by adjusting the relevant parameters such as taper velocity,taper time,taper velocity ratio,taper number,translation distance and so on in the control program.Furthermore,fiber grating sensing devices such as single taper,MZI,variable diameter optical fiber and LPFG sensor with different properties and applications are obtained.First of all,introduced to the transition and development of fiber optic sensor technology based on thermal deformation method,and simple introduction to structure and functional characteristics of electro-thermal fused biconical taper system in this topic.The single cone,MZI,LPFG and other fiber grating sensors with different shapes were obtained by adjusting different parameters of melt drawn cone.The morphology of optical fiber devices which with different tapered parameters was collected.And then we measured the sensing characteristics compared to explore the influence of different tapered parameters on the sensing characteristics.In addition,for LPFG with multiple periods,spectral transmission at different periods is recorded and corresponding sensor characteristics are measured.Secondly,this thesis introduces the technology of making variable diameter optical fiber by the method of electrothermal melt drawing cone,analyzes its basic principle,and conducts the actual variable diameter according to the theory,and then collects the variable diameter optical fiber morphological of different parameters to analysis and verification.Based on the idea of fused pull cone enhancing the coupling efficiency of fiber-optic sensing devices to improve the sensing characteristics,The single mode-no core-single mode sensor is tested by the variable-diameter technique described in this section.In the experiment,the sensing characteristics of tapered-single mode-no core-single mode sensor with different diameters and different lengths were tested.The experimental results show that the smaller the taper diameter,the higher of the refractive index sensitivity and the greater influence on the spectrum.At the same time,the longer the TSNS structure,the deeper of the interference fringes and the higher of the refractive index sensitivity.When the refractive index is 1.417,the refractive index sensitivity is the highest,reaching 1517.28 nm/RIU.Finally,based on the characteristics of multi-core fiber for space-division multiplexing and the all-fiber MZI principle,based on the variable diameter fiber technology described in Chapter III,the ordinary single mode-seven-core-single mode sensor is tapered and the corresponding sensor characteristics are measured.The experimental results show that the temperature sensitivity of the structure decreases from short wave to long wave.Selected four peak temperature sensitivity from short to long wave interference of 40 pm/oC respectively,24pm/oC,19 pm/oCand 16 pm/oC.In addition,the peak strain and refractive index sensitivity of the structure are consistent.Moreover,it can be concluded from the linear strain sensitivity that each interference peak is formed by the interference of the center core and the out core.This subject is based on the electrothermal fiber taping technology.Fabrication of fiber optic sensor device by using ring graphite heating resistance.By optimizing and adjusting the technological parameters of the tapered fiber,the coupler,variable diameter fiber,fiber grating and other devices with various performances can be made,and the sensing characteristics of the existing optical fiber sensor can be improved through the characteristics of the tapered fiber.