Fabrication Of Double-Clad Fiber Bragg Grating And The Investigation Of Its Characteristics

Fiber Bragg gratings (FBG) are key components in the fields of fiber communication, fiber sensing and fiber laser. The traditional method of fabricating FBGs was based on the use of excimer laser and a phase mask, however, the fabrication of FBGs in this thesis was carried out by use of femtosecond laser. This thesis is laid out along the line of theory analysis, simulation and experiment; its content can be divided into the following four parts.1. Introduction of relevant theories about FBGs, mainly about the coupled mode theory. There is also a brief analysis of ionization mechanism happened during the interaction between the femtosecond laser and dielectrics.2. A brief introduction of the FBG fabrication system, including relevant equipments, their parameters as well as their setup. Then, there is a detailed introduction about the procedures of adjusting the optical path.3. Different types of FBGs was fabricated under different the laser intensities, including gratings of TypeⅠ-IR and TypeⅡ-IR. And, their high temperature characteristics were investigated by use of annealing treatment.4. A model was setup for the profile transformation of the refractive index modulation in the annealing process, which could properly explain the phenomenon that bandwidth of Bragg gratings induced by Type I-IR and Type II-IR index change can be narrowed without the reduction of reflectivity when the annealing temperature was below a critical value.