HyFi Bragg: Proposal for the purchase of a laser for hydrogen free inscription of fibre bragg grating

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Fibre Bragg gratings are generally written in fibres with ultra-violet lasers, or more recently with femtosecond pulse lasers. In order to increase the refractive index change for the purpose of fabricating strongly reflecting gratings through the exposure to the lasers, it has been necessary to photosensitise the optical fibre by doping the fibre with boron and/or with high pressure hydrogen of order 200Bar. The latter requires special equipment and handling and is the only technique available to write good gratings in standard optical fibres with UV lasers. Femtosecond lasers can be used with hydrogen-free fibres, but are generally used in a point-by-point writing, or with care using a phase-mask. The quality of gratings can be variable, without great care being used.