Interferometer design for writing Bragg gratings in optical fibers

摘要

Bragg Gratings are waveguides, typically single-mode optical fibers, into which a periodic refractive index modulation has been imprinted by a patterned UV exposure. Fiber Bragg Gratings separate telecom frequency bands or compensate for optical dispersion in long-haul fiber networks, and also serve as strain sensors for civil engineering or geophysical studies and oil, gas or mining exploitation. A Bragg Grating writer is an interferometer for generating the UV exposure pattern. It is one of the unusual cases where an interferometer is a production tool, rather than a metrology instrument. In this paper, we review the most common Bragg Grating writing geometry and propose an opto-mechanical structure having minimal adjustment and very high mechanical stability.