Efficient fibre grating transmission filters

Linear Bragg grating resonators have recently been attracting much attention as the search for fibre compatible transmission filters continues. However, these structures are limited to applications that require only narrow stopbands. There remains applications that would benefit from the availability of broader bandwidth filters; either multi-passband or single passband. With that in mind an investigation into the feasibility of fabricating chirped Bragg grating resonators ensued. Two types of chirped resonator structures have been considered: Fabry-Perot and Moire gratings. The Fabry-Perot resonators comprise of two chirped gratings displaced by some distance along the length of the fibre. The Moire gratings comprise again of two chirped gratings but where the gratings are written directly on top of each other in the fibre one grating is shifted slightly in wavelength