Fiber Optic Bragg Grating Model

摘要

Photoinduced Bragg Grating in optical fibers were first demonstrated by Hill etal. in 1978. In 1988 Meltz, et al. developed an external Bragg grating writing technique which had more flexibility in the choice of the Bragg period. Since then and due to their unique properties a number of sensing concepts have been proposed and demonstrated. Most of these sensors are configured as back reflectors. A more general configuration, a Tapped Bragg Grating (TBG), was first demonstrated by Meltz et al. in 1991. A complete theory for the fabrication and operation of TBG's is still incomplete. In this report a simple model of Tapped Bragg Gratings is developed. This model will allow the understanding of the basic parameters necessary to fabricate TBG's. Several questions have to be answered to effectively fabricate a TBG sensor. Some of these questions are: What must the Bragg angle and period (Theta sub B and Delta sub B) be in order to effectively scatter radiation out of the fiber at a desired scattering angle Theta.