Spatial Division Multiplexing-Based Reflective Intensity-Modulated Fiber Optics Displacement Sensor

Recently,fiber optical sensors have been widely used in various aspects of the national economy.In particular,the reflective intensity modulated fiber optic displacement sensor(RIM-FODS)with the advantages of simple detection,flexible design,small footprint,stable performance and low in cost has attracted the user interests for on-site measurement.Meanwhile,the conventional single-core single-mode fiber(SSMF)is uncapable to satisfy the ever-increasing requirement of transmission capacity and data rate in the near future.Since the spatial division multiplexing(SDM)technique enabled by multi-core fiber,few-mode fiber and multi-core few-mode fiber can effectively solve the capacity crunch of traditional SSMF,it has stimulated worldwide research interests.In this thesis,the RIM-FODS based on space division multiplexing technique is put forward and experimentally demonstrated,and its sensitivity can be effectively improved together with successful reduction of corresponding dead zone range.The main research outcomes of the thesis are submarined as follows:(1)We establish the reflection model of RIM-FODS based on a pair of SSMFs and the output light field can be numerically simulated in order to obtain the intensity transfer function of RIM-FODS.Moreover,based on the MATLAB simulation platform,we comprehensive investigate the effect of SSMF parameters on the intensity transfer function,for the ease of performance optimization.(2)Since each channel of multi-core fiber is independent,a multi-core fiber-based RIM-FODS is designed to replace the traditional SSMF bundle configuration.Then,its feasibility of SDM enabled RIM-FODS is verified by numerical simulations.After the fan-in/fan-out devices for seven-core single-mode fiber and the seven-core few-mode fiber are in-hand,we build up a test platform of SDM enabled RIM-FODS test platform.In comparison with traditional RIM-FODS based on a pair of SSMF,the sensitivity of the front slope for multi-core single mode fiber based RIM-FODS is increased by 7.7 times and the dead zone is reduced by 20%.Furthermore,The results of seven-core few-mode based RIM-FODS indicates that,the sensitivity of the front slope can be further improved by11.2 times,and the dead zone is reduced by 37.5%.(3)In order to further explore the application of SDM technique,we introducemulti-input multi-output(MIMO)technology to improve the performance of RIM-FODS.Based on seven-core fiber based RIM-FODS,we carry out performance comparison among four different scenarios under the condition of dual input.The experimental results of seven-core few-mode fiber show that the dual-input scheme can improve the measurement range by 26%,while the dead zone range is reduced by 10%.