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Manufacturing Of Novel Optical Fiber Interferometric Sensors And Their Applications Research

Posted on:2015-01-09Degree:MasterType:Thesis
Country:ChinaCandidate:L XuFull Text:PDF
GTID:2268330422465729Subject:Mechanical Manufacturing and Automation
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Since OFS (Optical Fiber Sensor) has its unique advantages in sensor applications,it is now focusing much more on higher sensitivity, integration and networking, whichalso symbolized that OFS and its counter-part systems have functioned very well.Therefore, this paper mainly explores the OFS fabrication process as well asconstruction of OFS system with the following methods and innovations:(1) The improved method ofaMach-Zehnder interferomenter(MZI) is expounded.The MZIis fabricated to unparallel wall fiber micro-cavity by femtosecondlasermicromachining. The function Fiber optic sensor is converted into the not-functionoptic fiber sensor, which reduces the cost of time and money for fabrication. At thesame time, the analysis of theoretical model also confirmed this method, whichnotonly reduces the cost and improves the yield, but makes theindustrialization feasible.(2) This study proposes a new hybrid Mach-Zehnder interferometric (MZI)sensor based on two core-offset attenuators and an abrupt taper in a single-mode fiberfabricated by a fiber-taper machine and electric arc discharge. When the distancebetween the two core-offset attenuators is stretched to4500μm, significantinterference signals are detected with a prominent attenuation peak of~28dB. Theproposed MZI can be used to measure temperature due to its low refraction index (RI)and strain cross-sensitivity. The temperature sensitivity is34.95pm/℃and106.7pm/℃in the temperature ranges of14℃-250℃and250℃-1000℃, respectively.(3)This study proposes a high-temperature sensor based on an abrupt fiber-taperMichelson interferometer (FTMI) in single-mode fiber fabricated by a fiber-tapermachine and electric-arc discharge. The proposed FTMI is applied to measuretemperature and refractive index (RI). A high temperature sensitivity of118.6pm∕°Cis obtained in the temperature range of500°C–800°C. The wavelength variation isonly0.335nm for the maximum attenuation peak, with the external RI changedfrom1.333to1.3902, which is desirable for high-temperature sensing to eliminate thecross sensitivity to RI.(4) Anoptical fiber protection alarm system is built which mainly takes fiber Bragg grating(FBG) as sensitive element. The sensitivity of sensor isincreasedthrough the encapsulating. And the temperature sensor is applied, whichmakes temperature compensationfor allthe elements inside the system. When theintruders come into the protecting area, the system will detectthe places immediately,while the video camera systembegins to take snapshots. The whole process increasesthe safety of system.By the way, another system is also built with FBG and traditionalsensor, which is applied with fluid dynamic monitoring, and employsInternetprotocolsand485communication protocols. This system replaces the original method ofsampling test.Since the monitors can realize the parameters of the fluid by the consoledisplay, the difficulty of real-time monitoring with fluid will beresolved by thissystem.
Keywords/Search Tags:optical fiber interferometer, Mach-Zehnder interferometer, fiber-taperMichelson interferometer (FTMI), high temperature fiber sensor, femtosecond laser, optical fiber sensor system
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