<title>Material considerations for Bragg fiber gratings</title>

Abstract

In general, fibres designed for use in telecommunications systems are not sufficiently photosensitive to allow 'strong' fibre gratings to be written. This has led to the search for other silica-based fibres which exhibit enhanced photosensitivity without the need for hydrogen-loading, the boron co-doped germania fibre being perhaps the best known example. In addition, it is sometimes necessary to exclude dopants such as germania from the core as they would interfere with other desirable properties of the fibre. Prime examples are the rare-earth doped fibre laser and erbium-doped fibre amplifier, devices which may require low concentrations of germania in order to function properly. This paper will cover some of the advances that have been made in searching for new materials. the problems which have been overcome, and those which remain.