Research On Novel Polarization Beam Splitter And Sensor Based On Microstructure Optical Fiber

Microstructured optical fiber(MOF)has micron-level structural features and excellent optical performance.It is small in size,flexible in structure,good in stability,and has the characteristics of low loss,adjustable dispersion,and endless single-mode.The MOFs are widely used in optical fiber communications,lasers,optical fiber polarization,sensors and other fields.The MOF-based information transmission has higher signal strength and higher stability.The MOF-based lasers can generate high-power laser beams in a smaller space.The MOF-based polarization beam splitters have wide bandwidth of splitting beam,high extinction ratio,and short length of device.The MOF-based sensor has the advantages of high sensitivity and wide measurement range.The common MOFs include negative curvature fibers(NCFs)and photonic bandgap fibers.In this thesis,two kinds of polarization beam splitters with dual hollow-core NCF and the temperature and refractive index sensor based on the photonic bandgap fiber are proposed.The structure,transmission characteristics and beam splitting performance of the fiber polarization beam splitter are calculated and analyzed by using the finite element method and mode coupling theory.The loss characteristics and photonic bandgap of the photonic bandgap fiber are studied by using the finite element method and the plane wave expansion method,and the performance of the sensor based on this fiber is analyzed.The research contents and results in this thesis are summarized as follows:1.A broadband polarization beam splitter with the ten-tubes dual hollow-core NCF is investigated and designed.The optimal structural parameters of the polarization beam splitter are designed using a dual hollow-core NCF with ten tubes.The simulation results indicate that when the device length is 6.45 cm,the polarization beam splitting can be realized in the wavelength range of 1.23 μm-1.63 μm,its working bandwidth is-400 nm,covering the communication bands of the O+E+S+C+L,and its extinction ratio of high-order mode is higher than 100,which indicatdes that the fiber has excellent single-mode characteristics.2.A broadband polarization beam splitter based on NCF with an eighttubes dual hollow-core is investigated and designed.The optimal structural parameters of the polarization beam splitter are designed using the NCF with dual hollow-core and eight tubes.The simulation results indicate that when the device length is 6.45 cm,the extinction ratio of the polarization beam splitter is as high as 59 dB at the wavelength of 1.33 μm,the extinction ratio is as high as 47 dB at the wavelength of 1.64 μm,and in the wavelength range of 1.29 μm-1.73μn,the polarization extinction ratio is greater than 20 dB,and its working bandwidth is 440 nm,covering most of the O band and all the E+S+C+L+U bands.3.A temperature and refractive index sensor with high-sensitivity based on the photonic bandgap fiber is investigated and designed.A solidcore photonic bandgap fiber with six layers of air holes filled by the liquid is used to design its structural parameters and monitor the movement of the photonic bandgap by monitoring the movement of its loss spectrum,thereby realizing the temperature and refractive index sensing.According to the simulation calculation,the maximum sensitivity of the temperature sensor is 5.10 nm/℃,and the average sensitivity in the temperature range from-40℃ to 40℃is 4.43 nm/℃.The maximum sensitivity of the refractive index sensor in the range of 1.48-1.58 is 13325 nm/RIU,and the average sensitivity is 8772 nm/RIU.In this thesis,the polarization beam splitter and sensor are investigated and designed by using the dual hollow-core NCF and photonic bandgap fiber,and their excellent beam-splitting and sensing performances are obtained,respectively.And a new type of polarization beam splitter with the hollow-core NCF and the sensors with solid-core photonic bandgap fiber are realized.The design ideas and research results of the two types of devices provide a useful reference for the future development of high-performance polarization beam splitters and sensors.The further development and practical application of the two types of devices will play important roles in promoting the development of the communication systems with large-capacity and hollow-core fiber,integrated sensing field,and so on.