Study On The Interferometric Fiber Optic Sensor Based On Bending Two Mode Fiber

In the progress of sensor research,optical sensor has been widely used for measurement of various parameters and plays an important role in medical biology,bridge construction and other fields.In this thesis,two kinds of bending interferometric optical fiber sensors are designed and fabricated using dual-mode optical fiber(TMF).The temperature,glucose content and micro-displacement characteristics are studied respectively.The main contents of this thesis are as follows:1.An interferometric optical fiber sensor based on a bent dual-mode fiber spindle structure is designed.The SMF-TMF-SMF(STS)structure is bent by flame baking to form an optical fiber sensor with spindle structure.TMF length is 3 cm and bending diameter is 4 mm.In the range of 0%-21% glucose brix,the sensitivity of the sensor is0.368 nm/%.When micro-displacement increases from 0 to 80μm,the displacement sensitivity of the sensor is-0.298 nm/μm.It is temperature-insensitive in the range of10-70°C,which effectively avoids the influence of temperature on glucose brix and micro-displacement measurements.The sensor is stable,easy to integrate and simple to fabricate.It can be used in the fields of biomedicine and industrial automation.2.An interferometric optical fiber sensor based on a U-shaped bended dual-mode optical fiber is designed.The sensor structure is formed by further processing and baking on the basis of the spindle structure.The results show that when the bending diameter is 1 mm,the sensitivity of glucose is as high as 1.544 nm/%,and the range of glucose brix is 0%-12%.When the bending diameter is 2.5 mm,the micro-displacement increases from 0 to 80μm,the measurement sensitivity of the sensor reaches-0.174nm/μm.It is temperature-insensitive in the range of 10-70°C.Compared with the traditional manual bending optical sensor,the sensor is more compact and has higher glucose brix sensitivity.It has good application prospects in fermentation production,biomedical and other fields.In summary,two novel bent optical sensors have been developed to measure glucose content and micro-displacement,which are insensitive to temperature.The first one bends special optical fibers and makes a novel spindle-shaped optical fiber sensor by flame burning,which is suitable for measuring micro-displacement.The second is to further process a compact U-shaped structure based on the spindle structure,which improves the sensitivity of glucose brix measurement and is suitable for glucose brix measurement.