Applications Of Microsturctred Fiber Gratings And THz Waveguide Devices

Fiber grating sensing as one branch of optical fiber sensing technology, plays a pivotal role in various sensing situation, such as bridges, tunnels, water safty, pretrochemical and biochemical fields. Since2000, the rise of microstructured fiber Bragg grating, opens up new fields for fiber grating sensors. With the development of Internet of Things and the proposal of Smart City, people are more urgent for fiber optical sensors and meanwhile put forward higher requirements on it. On the other hand, due to the development of ultrafast laser technology, terahertz technology is becoming a hot research field. Owing to its special properties compared to other bands, terahertz technology has very important applications in basic research, safety monitoring and biomedicine research. But because of its particularity, it is still lack of effective transmission medium, and relative waveguide filters and sensors. In this thesis, theoretical and experimental study of microstructured fiber Bragg grating sensing and THz waveguide devices including the relevant research results are elaborated. The main contents include:At first, we describe the broad market demand on optical fiber sensing especially fiber grating sensing applications, as well as the status and development of the terahertz technology, in order to highlight the necessity and importance of our research. Then we introduce the history and research status of fiber grating and microstructured fiber, respectively. Describe the background of THz technology and the current research situation of THz waveguide. After that, the two parts of my research are addressed.The first part is the sensing research based on microstructured optical fiber Bragg grating (MOFBG). Using Coupled Mode Theory, the mode characteristics of MOFBG, are mathematically analyzed, as well as the refractive index and temperature sensing modal. The process for preparing MOFBG is described, and through experiments, it’s demonstrated that the MOFBG can solve the cross-sensing problem of temperature and refractive index. Next, it focuses on presenting a reflection-type acetylene gas sensors based on MOFBG. The sensing principle, preparation methods and structural optimization process are described. Finally the sensor is successfully fabricated and experimental detection the concentration of acetylene gas is realized.The second part is the study of terahertz waveguide devices. The current terahertz devices, especially THz filter are reviewed. From the generation and detection of THz, the terahertz time-domain system (TDS) is introduced and data analysis process is presented as well. Design and manufacturing process of THz fiber Bragg grating are detailly described, and the first time, terahertz FBG sensing application is realized by paper thickness detection. Further more, a narrowband filter is proposed by inserting a periodic structure into two-wire metal waveguides. The mode characteristics and coupling coefficients are theoretically studied. The filter is experimentally fabricated and tested.Finally a novel silk protein foam based THz waveguide is researched for the first time as we known. By introducing the structure properties of silk and applications in optoelectronics, the research background is detailed. The preparation of silk foam fiber is elaborated. The silk foam block and fiber samples are tested by using the TDS system. Combined with the umerical simulation the THz transmission properties of silk foam fiber are discussed.