Research On Sensing Properties Of Polymer Optical Fiber Grating

As a passive optical component, fiber grating has the characteristics of small size, light weight, lower cost, and immune to electromagnetic interference, so it is widely used in sensing fields in recent years. Recently, polymer optical fiber fabricated from polymer materials emerges in recent years as a special material fiber. Except for the advantages of the conventional optical fiber, it also has good flexibility, excellent biocompatibility, small Young's modulus, and humidity optical sensitive properties. The researches on polymer optical fiber grating on temperature sensing, strain (or force) sensing, humidity sensing, and bending sensing contribute to finding the advantages in sensing fields and further expanding the application scope of polymer optical fiber grating.In this thesis, we take the polymer fiber Bragg grating (POFBG)made of polymethyl methacrylate (PMMA) material as the research object. We study the basic sensing characteristics of POFBG theoretically and experimentally, and propose the high sensitivity vector bend sensing based on the two kinds of fiber gratings. The research works in detail are as follows.Firstly, we introduce the development, classification and sensing applications of silica fiber grating and polymer optical fiber grating. We summarize the advantages of polymer fiber grating in the sensing field and illustrate the background and significance of this topic. Secondly,according to the general analytical methods—coupled mode theory and transfer matrix method, the properties of POFBG for sensing of the temperature, strain, humidity, and bending have been simulated and compared with those of silica optical fiber Bragg grating from the aspects of simulation and experiment. The experimental results are basically consistent with the simulation ones, which further show the advantages of POFBG sensors. Thirdly, by combining silica fiber Bragg grating with POFBG, we propose a bending sensor with high sensitivity, which can discern the bending direction by the wavelength discrimination between the silica fiber Bragg grating and POFBG. The sensitivity of this proposed sensor achieves up to 0.94 nm/m-1 in the range of ±4.2 m-1.Finally, the experimental results are summarized, and the future research direction and methods are discussed.