Tailoring The Spectrum Of Fiber Gratings And Its Applications

A fiber grating emerged in 70ths of last century. As a passive filter, it has been applying in both fiber communication and sensing system, because it has many advantages such as small bulk, low cost, easy connection and compatibility and is sensitive to temperature, strain etc. Scientists have studied on the inducing mechanism, imprinting, compacting and reconstructing of fiber grating for more than thirty years. With the development of fiber communication and sensing system, varies kinds of spectrum shape of fiber grating are needed, which is the base of the subject of my dissertation.In my dissertation, the mechanism, characteristics of the spectrum, growth and tailoring the spectrum shape of fiber grating are theoretically and experimentally studied and the results expected are achieved.The contents of my dissertation mainly includes:1. We firstly summarize the development of fiber grating in theory, imprinting technique and its applications.2. A formula about the relation ship between photo-induced index increment of photosensitive fiber and its irradiating dose is deduced based on my new hypothesis according to the"color model"theory. The formula that is a good fit to our experiment is the base of my further study.3. We have studied on the photo-induced birefringence of photosensitive fiber. Two kinds of method for measuring the birefringence are proposed based on a Mach-Zehnder interferometer and a fiber loop, respectively.4. We have calculated the spectra of uniform fiber Bragg gratings, uniform long period fiber gratings, chirped fiber Bragg gratings, sampled fiber Bragg gratings and phase shifted fiber Bragg gratings based on transmitted matrix of coupled mode theory.5. The effective indexes of fiber core and clad, the electric field of mode and coupled coefficient of two modes are calculated theoretically. We design amplitude masks of long period fiber gratings based on the calculating results.