Research On Structural Design And Sensing Characteristics Of Special-Shaped Optical Fiber Sensor

The special-shaped optical fiber sensor inherits the advantages of good stability,corrosion resistance,acid and alkali resistance,electromagnetic interference resistance,light weight,small size,and low cost.Compared with traditional sensors,transmission loss of the special-shaped optical fiber sensor is reduces.Laser surface processing technology brings a new revolution to fabricate special-shaped fiber sensors.The research content of this article is as follows:(1)The application of CO₂ laser technology in the manufacture of special-shaped optical fiber sensors is discussed.(2)This paper presents a design scheme of asymmetrical special-shaped fiber optic sensors.Based on the theory,simulation,and experiments,a series of analyses are performed on the sensor.For curvature sensing,the maximum sensitivity of the sensor is 5.412 nm/m^-1,the minimum sensitivity is 4.477 nm/m^-1,and the average sensitivity is 4.941 nm/m^-1 in IFP(Indirect Fusion Portion).In DFP(Direct Fusion Portion),the maximum sensitivity is-3.194 nm/m^-1,the minimum sensitivity is-1.033 nm/m^-1,and the average sensitivity is-1.911 nm/m^-1.Sensitivity decreases linearly with the increasing of curvature.The direction of wavelength drift is related to the bent direction,so it can be used to detect the bent direction.The concept of additional light intensity loss is introduced,which explains that the transmission spectrum loss of sensor increases in different bent directions.(3)A design scheme of a bi-symmetrical special-shaped fiber sensor is proposed and implemented.Combined with the basic principle of the sensor,paper studys the influence of the writing depth and the spacing of the writing area on the spectral characteristics,and discusses the principle of temperature sensing for the sensor.The temperature sensing characteristics of the sensor are studied in simulation and experiments.In the range of room temperature(21.6°C)to 85°C,the temperature sensitivity can reach 224.52 pm/°C;the resonant wavelength moves to the direction of long wavelength with the increasing of temperature.(4)The design schemes of the two types of cascaded shaped optical fiber sensors are proposed,and the basic principles of the dual cascaded shaped LPFGs are discussed in detail.The sensitivities of the two LPFGs are-18.13 nm/RIU and-17.57nm/RIU in the range of refractive index range from 1.3300 to 1.3968,respectively.The overall sensitivity of the cascaded LPFG is-20.92 nm/RIU,which is increased to15%and 19%.(5)The light intensity loss model analysis method is proposed and applied to the analysis of the spectral characteristics of the dual cascaded special-shaped LPFGs for the first time,to the best of our knowledge.Bysummarizing the general form of the light intensity loss model,this model has great application prospects for cascaded and even more forms of sensors.