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Study On Structures And Characteristics Of Novel Fiber-Optic Fabry-Perot Interferometric Sensors

Posted on:2010-08-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:M DengFull Text:PDF
GTID:1118360275474157Subject:Optical Engineering
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Optical fiber sensing technology has attracted much attention internationally due to their advantages, including immunity to electromagnetic interference, intrinsic safety, and capability for remote control, etc. As an important member of optical fiber sensors, Fabry-Perot interferometric sensors have been successfully commercialized and widely used in many fields as they have a number of unique advantages, such as small size, high resolution, good stability, and low cost, et al.The design and fabrication techniques of existing F-P interferometric sensors are studied systematically in this dissertation. Based on the previous work, we proposed and fabricated two types of novel miniature fiber F-P interferometric (MFFPI) sensors, which will enrich the structures of MFFPI sensors. The main contents are given as follows:①Based on the multi-beam interference principle and the propagation equation of Gaussian beam in the free space, the expression of the reflective intensity for the Gaussian beam passing through a F-P cavity is theoretically analyzed. The influences of non-parallelism of the F-P surfaces on the intensity and fringe visibility of the reflective beam have been numerically simulated and the results show that both intensity and fringe visibility of the reflective beam are nonlinearly reduced with the increment of the non-parallelism of the F-P surfaces, which provides theoretical foundation for fabricating MFFPI sensors with high fringe visibility.②The optical and sensing features of fused F-P interferometric sensors based on photonic crystal fibers (PCFs) have been theoretically studied. It indicates that: (1). The fringe visibility of the fused F-P interferometric sensors based on PCFs is only determined by the reflectivities of two reflective surfaces and the transmission loss of the first reflective surface, which provides the theoretical guiding for the fabrication of PCF-based F-P interferometric sensors with high fringe visibility; (2). The temperature sensitivity of the F-P interferometric sensors based on TIR-PCF depends on the thermo-optical coefficients of pure fused silica and the effective refractive index of cladding, whereas the F-P interferometric sensors based on PBG-PCF has relatively small temperature sensitivity due to the small thermo-expansion coefficient of pure fused silica. ③The mechanism and features of femotosecond laser micromachining are analyzed and an asymmetry MFFPI sensor structure with high fringe visibility is successfully fabricated on a single-mode fiber by using femtosecond laser processing, ultrasonic wave cleaning, double creating, and chemical etching.④The sensing characteristics of asymmetry MFFPI sensors including temperature, strain, and refractive index are experimentally studied. The experimental results show that: (1). The asymmetry MFFPI sensor is less sensitive to temperature, and its wavelength-temperature sensitivity is ?0 .002 nm /oCfor 20 ~100oC , and the all-fiber structure of such a sensor can survive in high temperatures; (2). The asymmetry MFFPI sensor is more sensitive to strain, and whose wavelength-strain sensitivity can be up to0.006 nm /μεfor0 ~ 360με, based on this optical strain gauge without temperature compensation can be designed; (3). The open micro rectangular notch of an asymmetry MFFPI sensor can make gaseous or aqueous samples enter/leave the F-P cavity freely, and it has high refractive index sensitivity.⑤For the first time, the structure and the fabrication process of a F-P tip sensor based on TIR-PCF are proposed to our knowledge. The sensing characteristics of such a sensor are investigated by theory and experiment. It shows that the fringe visibility of the F-P tip sensor based on TIR-PCF is sensitive to refractive index, and the sensitivity, repeatability and resolution for refractive index measurement in the linear operating range are ~4.59/RIU,±0.5%FS and ~2x10-5, respectively. In addition, such a sensor can be used as an excellent temperature sensor with a cavity-length-temperature sensitivity of 18.721nm/ oC and a±0.15%FS repeatability when tested from 20oC to100oC . More importantly, the refractive index measurement based on the fringe visibility is independent of temperature change. Therefore, such a sensor can be used to simultaneously measure temperature and refractive index.
Keywords/Search Tags:Optical Fiber Sensor, Fiber-Optic Fabry-Perot Interferometers, Photonic Crystal Fiber, Femtosecond Laser Micromachining, All-Fiber Devices
PDF Full Text Request
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