Research On Temperature Sensing Characteristics Of Waist-enlarged Cascaded Few Mode Fiber

Optical fiber sensors are widely concerned by domestic and foreign researchers because of their small size,strong adaptability,high sensitivity and can be used in a variety of harsh environments.The waist-enlarged fiber structure is simple to fabricate and can improve the sensor performance,while the few mode fiber(FMF)has the characteristics of controllable mode and low fusion loss.Thus,it is of great practical significance to study the FMF temperature sensor based on waist-enlarged fiber structure.In this paper,on the basis of summarizing the research status of waist-enlarged fiber sensors at domestic and abroad,four kinds of waist-enlarged cascaded FMF sensors with different structures are prepared.The temperature sensing characteristics of the sensors are studied in detail.Specific contents include:Firstly,the transmission mode of the FMF is analyzed and simulated.Based on the principle of mode interference,the principle of waist-enlarged cascaded FMF sensor is analyzed.The influence of temperature on the transmission spectrum is studied.Secondly,the preparation method of waist-enlarged fiber is introduced and the main parameters affecting its size are explored.The beaded shaped FMF sensors are designed and fabricated.The transmission spectrum and mode changes of beaded shaped sensors with different waist-enlarged fiber sizes are studied.The temperature experiment of sensors are carried out,and the temperature sensitivity and linearity of the sensors are analyzed.Next,the dual gourd shaped FMF sensors are designed and fabricated.The transmission spectrum and mode changes of the dual gourd shaped sensors with different lengths are studied.The temperature experiment of sensors are carried out,and the temperature sensitivity and linearity of the sensors are analyzed.Then,the pagoda shaped FMF sensors are designed and fabricated.The transmission spectrum and mode changes of the pagoda shaped sensors with different waist-enlarged fiber sizes are studied.The temperature experiment of sensors are carried out,and the temperature sensitivity and linearity of the sensors are analyzed.Finally,fructus sophorae shaped FMF sensors are designed and fabricated.The transmission spectrum and mode changes of the fructus sophorae shaped sensors with different lengths are studied.The temperature experiment of sensors are carried out,and the temperature sensitivity and linearity of the sensors are analyzed.