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Studies Of Long-period Fiber Grating Based On Micro/Nano-Fiber

Posted on:2017-04-03Degree:MasterType:Thesis
Country:ChinaCandidate:L ZhaoFull Text:PDF
GTID:2308330485466180Subject:Materials engineering
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Today, fiber is more and more important in people’s life. With the development of fiber-optical communication technology, optical components become more and more minim too. Now there is a new micro-nano fiber which has smaller size and lower loss, these advantages make it be a better selection in the communication and sensing field.Fiber grating sensor is very widely used in some special environment because it has high sensitivity, low weight, simple structure, small size, low environmental requirement and it’s without the interference of electromagnetic. Long-periodic fiber grating (LPFG) has hundreds micrometers period, and it has higher sensitivity and measurement accuracy than fiber Bragg grating. This thesis will introduce micro-nanofiber based LPFG.At first, we introduce the development history and features of micro-nano fiber. Secondly, we talk about some methods to make micro-nanofiber LPFG.We use hydrogen flame to make up for deficiencies in the alcohol lamp heating method. In this way, we a fix single-mode fiber on two translation stages, and remotely control motors to move to opposite directions simultaneously by a computer, then use a hydrogen flame to heat the fiber. It can make different diameters of micro-nano fibers by controlling displacement and moving speed of translation stages.We can also make micro-nanofiber by a carbon dioxide laser. We heat a fiber by a carbon dioxide laser, stretch it by the action of the gravity and get micron-sized micro-nano fiber at last. In this way, we get different diameters of fibers by changing laser’s power. We also can stretch overlength micro-nano fiber by adding a direct current machine and winding rods on the translation stages. But the surface quality of the fiber is worse than which is made by a hydrogen flame. Besides, it has higher losses because the unstable power of laser results in nonuniform diameters of the fiber.Thirdly, we expound LPFG and analyze it by coupled mode theory. For now, there are many different making methods, such as UV-writing, ion implantation, high frequency carbon dioxide laser writing, arc discharging, etching, femtosecond laser writing and mechanically induced method. We introduce UV-writing, high frequency carbon dioxide laser writing and mechanically induced method which are most often used in the lab. Then we talk about how to make machinery slightly curved ring LPFG using a micro-nano fiber. Comparing to other methods, this process flow is simple, low-cost, feasible and high quality. It uses a rotatable stage to warp a micro-nano fiber on a bunch of single-mode fibers. The refractive index is changed at the point of contact between micro-nano fiber and single-mode fiber, and the fundamental-mode will be coupled to high-mode modes. In this way, grating is realized by periodic bending.. In the experiment, we also analyze the relationship between the diameter of fiber rod and period of LPFG, analyze the relationship between resonant wavelength and period of grating, discuss the coupling between different modes and calculate the resonant wavelength of a fiber grating.
Keywords/Search Tags:micro/nano-fiber, long-period fiber grating, resonant wavelength, coupling
PDF Full Text Request
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