Fiber Bragg Grating Flow Rate Sensor Based On Light Wave And Photonic Microwave Technology

In recent years,fiber sensors have been applied in many fields,including bridge and tunnel projects.The reason why fiber sensors developed so quickly is that fiber sensors have many advantages such as volume and quality are small and antielectromagnetic interference etc.Fiber Bragg grating flow velocity sensor with light wave and microwave photonics is studied in this work.This thesis is mainly divided into four parts: The first section introduces some basic concepts and the classification about fiber sensors,and roughly presentes relevant concepts and the implication about Microwave Photonics.The second section introduces one of the important fiber sensors – fiber Bragg grating sensors particularly,including the making and the structure of fiber Bragg grating,and the sensor principle of the fiber Bragg grating sensors.Due to fiber Bragg grating is usually used to do temperature or straining experiment,so we particularly analyze three sensor models – temperature sensor model,straining sensor model,temperature and straining interact sensor model.The third part proposed a novel fiber Bragg grating flow velocity sensor based on cantilever with variable width.In our design,the flow velocity sensor which induces the cantilever structure is stainless steel materials and fiber Bragg grating is tied in the special space of the cantilever.The cantilever structure is a entirety which consist of the part of rectangle and the part of trapezoid and the two parts do not need peg to fix them on.The head of the designed sensor do not add any other weight which can improve sensitivity,and the whole system is easy to make.These is a reference fiber Bragg grating in the sensor device which is used to compensate the variety of temperature,and it is making the experimental results are not affected by temperature changes.The scheme indicates that there exists a good linear relationship between the drifting of the wavelength of the fiber Bragg grating with the flow velocity.By calculation,the sensitivity of the proposed sensor is 0.025m/s,and the measuring range of the flow velocity sensor is from 0m/s to 2m/s approximately.The scheme not only compensates the change of temperature,but also improves the sensitivity of the sensor.Last part presentes a fiber Bragg grating sensor based on microwave phase shifting measurement,we obtain the direct proportion between weight and the microwave phase shifting after fitting the experimental data.