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Research On Coupling And Sensing Characteristics Of Mulit-core Structure Fibers And Photonic Crystal Fibers

Posted on:2015-09-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:H M HeFull Text:PDF
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With the gradually improvement of fiber and photonic devices in fabricationtechnology, there are a variety of novel unique properties and structures fibers, and ithas become a necessarily development tendency to exploit the new photonicinstrument. The multi-core fibers have attracted much attention due to its low-costand high-denseness properties in the optical sensing fields. Fiber sensor based onmulti-core fibers not only have compact, convenient and flexible, but also can realityof simultaneous measurement of multi-parameters. This dissertation mainlyinvestigates the multi-core (include conventional fibers and photonic crystal fibers)and its applications in fiber optic sensors. On the one hand, the sensing character ofconventional multi-core fiber has been theoretically and experimentally researched,on the other hand, several new structure of multi-core fibers have been proposed, theconstruction, features and applications in the optical sensing fields are discussed bynumerical methods. We also have investigated the sensor based high birefringencephotonic crystal.Based on the far-field interference fringe pattern, the theoretical model for theconventional multi-core fiber sensor was established and discussed. Based oncoupled-mode theory, the theoretical model of the four-core fiber gratings ontransverse and bending is discussed. Using numerical method, the four-core fiberBragg gratings transverse force sensing rules according to transverse load andorientation, fiber outer diameter was reported, and the bending characteristics offour-core optical fiber Bragg grating according to bending curvature and bendingdirection is analyzed. A new structure multi-core fiber (D-shaped four-core fiber) wasproposed and its bending sensing theory was studied, the bending sensing rules andthe relation with the thickness of side-polished have been studied by numerical, andits bending sensitivity is higher than that of the usual four-core fiber grating.A type of high birefringence dual-core photonic crystal fibers by combining circularand elliptical air holes in fiber cladding has been proposed, included by asymmetricfiber core style and asymmetric fiber cladding style. The transverse electric fieldvector distributions of the two modes are evaluated, the birefringence or couplinglength with the different parameters are numerically analyzed basing on finite-elementmethod. The proposed structure combines high birefringence and short coupling length perfectly, which provide a great application value in high performance opticaldevices, such as optical fiber coupler or polarization splitters.A novel hydrostatic pressure sensor based on a dual-core photonic crystal fiber withasymmetric cladding by combining different sizes of elliptical air holes was proposed.The theoretical model of hydrostatic pressure sensing was established and discussed.The transmission spectra of sensor under hydrostatic pressure and the relationshipbetween pressure sensitivity and the minor axis ratio at different elliptical ratios havebeen numerically investigated. The results show that we proposed sensor has higherpressure sensitivity than that of conventional dual-core photonic crystal fiber whichhas the circular-hole.We research the output spectrum response of double-core photonic crystal fiber andits applications in sensing fields. First, we proposed two types interferometer basedvarious theory patterns, one is double-core photonic crystal fiber Mach-Zehnderinterferometer, and the other is double-core photonic crystal fiber Mode couplingsinterferometer. We established and analyzed the theoretical model and fabricated theinterferometer sensor based double-core photonic crystal fiber. Then, transverse forceand curvature characteristics of the interferometer sensor based double-core photoniccrystal fiber were theoretical studied. Finally, transverse force and curvature areexperimentally investigated. Measurement of transverse force or bending curvature isrealized by monitoring the wavelength shift of the transmission spectrum. Thewavelength shift is temperature insensitive and the experimental results areconforming to the theory model.The applications of high birefringence photonic crystal fiber (HB-PCF) in sensingfields were investigated. We fabricated the Sagnac interferometer based HB-PCF, andestablished and analyzed the principle model for strain sensing, and then theexperimentally demonstrated is given. The problem of splice between the filled liquidHB-PCF and standard single mode fiber (SMF) was experimentally studied. Thetemperature sensor based filled liquid HB-PCF Sagnac interferometer was fabricated,and its temperature sensing characteristics were investigated in theoretical andexperimental. The sensor is temperature insensitive and the experimental results areconforming to the theory model.
Keywords/Search Tags:multi-core fiber, dual-core photonic crystal fiber, high birefringencephotonic crystal fiber, coupling-mode theory, fiber sensor
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