Novel fiber sensing schemes designed for liquid parameters analyzing

• Main Authors: Shih-syuan Hong, 洪士軒
• Other Authors: Shien-Kuei Liaw
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/39143988739013337936

碩士 === 國立臺灣科技大學 === 電子工程系 === 102 === This thesis presents research on liquid characteristics sensing system using fiber grating. The key sensing parameters are liquid solution refractive index, liquid temperature and liquid level. First of all the introduction of fiber gratings used in this thesis---tilted fiber Bragg grating (TFBG), long period fiber grating (LPFG) and fiber Bragg grating (FBG) is given; including the working principles and manufacturing process. Using 1584 nm phase mask and tilting four degrees to generate the best cladding modes. Using TFBG and LPFB to monitor the refractive index of sugar solution and the sensing principles are discussed. The variation and the R square of TFBG based sensors are 3.178 nm/n and 0.9981, respectively; the variation and the R square of LPFG based sensors are -32.699 nm/n and 0.9715, respectively. Next is using TFBG and LPFG to monitor the liquid temperature. The variation and the R square of LPFG based sensors are -0.36nm/℃ and 0.9857, individually; the variation and the R square of TFBG based sensors are 0.0094nm/℃ and 0.9966, respectively. The advantages of two different sensing heads are combined to sense variations of index and temperature at the same time so they can calibrate with each other. The last part is water level sensing experiment, which is using LPFG to carry out the accurate level sensing. The result is 1.494 nm/cm with up to 0.1cm accuracy, and the sensing range is 2.1 cm depth. Pasting the FBG on carbon fiber reinforced plastic (CFRP) to make a water pressure sensor in order to achieve a larger water level range sensing; and introducing the linear-cavity fiber laser sensing system at the same time. The result is -0.00304 nm/cm with up to 10 cm accuracy, and the sensing range is 130 cm depth. Changing the thickness of CFRP to adjust the sensing range and the accuracy of the sensing system is also studied.