Fiber Grating Writing And Its Application

Basing on photosensitivity of Ge-doped glass fibers, fiber gratings are constructed by varying the refractive index of the core lengthwise along the fiber, they are new type of optical components. From successfully fabricating of the first fiber grating to now, not only fabrication methods, but also theory researching and applications are all have fast development. Fiber gratings have several distinguished advantages, such as: all-fiber geometry, high return loss or extinction, low insertion loss, small bulk, and potentially low cost etc. Desired spectral characteristics can be achieved through varing numerous physical parameters, these parameters including induced index change, length, apodization, period chirp, fringe tilt, and whether the grating supports counterpropagating or copropagating coupling at a desired wavelength. By reconstruction of fiber gratings, various fiber grating devices, which have different spectral shapes, can be designed.In this thesis, spectrum characteristics, fabrication method, applications and design of fiber gratings, are theoretically and experimentally studied. The main work is provided as follows:1. Firstly, the development history, classification, theoretical analysis methods, imprinting techniques, applications and design methods of fiber gratings are summarized.2. The characteristics of fiber Bragg gratings and long period fiber gratings have been studied by means of the coupled-mode theory. The transfer matrix approach which treats with non-uniform fiber gratings has been introduced. The effective refractive index of core mode and the first-rank cladding modes of the C598-302(s) photosensitive fiber, which is supplied by No. 46 Institute of the Information and Industry Ministry of China, have been calculated with the three-layered step-index fiber model. The relations between grating period and the temperature, strain sensitive characteristics of long period fiber gratings have been analysed, with drawing the relation curves between grating period and resonant wavelength of the first-rank cladding modes.3. Basing on the"color model", a multi-decaying-exponential formula...