Photorefractive effects in optical fibers grating fabrication and characterization

The objectives of this research were (1) to develop experimental techniques to form the technical basis for fabrication of high efficiency, uniform photorefractive fiber Bragg gratings, and (2) to characterize the fiber grating spectrum behaviors under influence of environment effects for applications in fiber sensor systems.; A phase grating, was designed and developed using photolithographic techniques. The phase mask exhibiting large uniform effective area and high laser power tolerance provided a special diffractive pattern required in fiber grating fabrication. A phase mask with less than 2% depressed zero order efficiency has been produced.; Using the phase mask technique, photorefractive fiber Bragg gratings were successfully recorded in optical fiber core using a written wavelength of 248 nm. Specially designed fiber gratings exhibited measured diffraction efficiencies of 99%. The resonant wavelength of the fiber grating was centered at 1.28 {dollar}mu{dollar}m with FWHM around 0.3nm.; The fiber grating frequency response under different writing conditions was studied which provided the information for designing and fabricating gratings for many special applications. A high resolution, low noise, and large dynamic range measuring system established in this research proved to be a powerful tool for the study of fiber grating properties. Environmental effects on the fiber grating center wavelength were investigated under externally applied temperature and strain perturbations. The linear relation between the applied perturbation and grating wavelength shift demonstrated that these gratings are very effective devices for optical sensing functions. The simultaneous strain and temperature sensing analysis showed a realistic model for this application.