The Research On Tilt Sensor Based On Fiber Bragg Grating And Mode Interference

Compared with the traditional electronic tilt sensor,the fiber tilt sensor has obvious advantages such as reusability,light weight,high sensitivity,and low cost.In recent years,during the construction process of large-scale buildings such as sports halls,swimming pools,and commercial high-rises,the health measurement of foundations has become an increasingly popular topic.Optical fiber tilt sensors have also received widespread attention.However,current fiber tilt sensors generally have the disadvantages of small measurement range and low sensitivity.This dissertation mainly focuses on the fiber-optic tilt sensing system,and focuses on the research of fiber-based Bragg gratings and mode interference tilt sensors.The main work is reflected in the following three aspects:(1)Based on the principle of fiber optic sensing technology,a new type of fiber-optic tilt sensor structure was designed.The sensor has simple structure,stable detection performance,good mechanical performance,and strong anti-interference ability,and is suitable for various complicated environments.This article focuses on the theoretical basis and measurement principle of the tilt sensor structure design.Based on this new type of tensile structure,a fiber Bragg grating tilt sensor was designed and theoretically analyzed and experimentally studied.The experimental results show that the sensitivity of the optical fiber tilt sensor based on fiber Bragg grating can reach 0.6109nm/deg and the linearity is good within ±8° of the measuring range.The sensitivity of the stretched fiber Bragg grating tilt sensor,which has been referred to,is 0.032 nm/deg,which is a factor of up to 20 times higher than the sensitivity.(2)For the tilt sensor based on mode interference,including the concept of few mode fiber,a comparative analysis of the M-Z interferometer based on the few mode fiber was performed.In this paper,the strain characteristics of few-mode optical fibers are analyzed.Based on a new type of tensile structure and few mode fibers,a mode interference tilt sensor was designed and theoretically analyzed and experimentally studied.The experimental results show that the tilt sensor based on mode interference has extremely high detection sensitivity of 2.5702nm/deg and good linearity within the measurement range of ±8°.The sensitivity of the interferometric tilt sensor that has been consulted can reach 2.346nm/deg,which is more sensitive than that of the interferometric tilt sensor.In addition,the tilt sensor based on the core mode interference is more stable and simpler to fabricate.(3)The strain-sensitivity experiments for cladding reduction of fiber Bragg gratings and few-mode fibers were performed.The experimental results show that:The strain sensitivity of optical fiber Bragg grating with diameter of 95?m corroded is 1.71 times before corrosion,and is inversely proportional to the square of its diameter.The strain sensitivity of small-mode optical fiber corroded to 95?m in diameter is 1.37 times before corrosion,which can effectively improve its strain sensitivity.