Fabrication And Sensing Characteristic Of Tapered Fiber Bragg Grating

With the improvement of FBG's theoretical and production technology, fiber sensor technology has been greatly developed. However, the cross-sensitivity becomes the key problom on the measurement of temperature and strain with the fiber Bragg grating. Temperature and strain will both cause the changes of FBG's wavelength peak. Detection with a single fiber grating can not distinguish the change cause between temperature and strain, which has restricted the FBG sensors' development. Domestic and foreign research shows that using special fiber grating can solve this problem. Therefore, a research on the cone-shaped fiber Bragg grating fabrication and demodulation was present in this paper.Fiber Bragg Grating coupled model analysis showed that when optical fiber cladding is tapered, the fiber Bragg grating effective bandwidth broadens when under stress but to be insentient to the temperature, which is similar as the characteristics of the chirped FBG. The different cone-shaped fiber Bragg gratings is fabricated by chemical methods with different concentration of corrosion solution. A deep analysis about the sensing characteristics of these gratings was present.Based on singlechip, a corrosion control system of the cone-shaped fiber Bragg grating was designed. By regulating the speed of electric moving stages, the etching speed of fiber was controlled and the cone-shaped fibers were produced. The software (CausticControl) of controlling the etching process was developed. The temperature and strain testing systems were constructed, and.based on these the sensing characteristics were measured and calibrated by the spectrograph. The result was verified.The results of strain and temperature of different taper FBG shows that: the center wavelength of the tapered fiber grating moves towards the long-wave direction and the bandwidth broadens when stress increases. The more the cone angle increases, the more sensitive the bandwidth broadens under stress. They are in a good linear relationship; the changes of temperature have no effect on the bandwidth of cone-fiber grating.