Fremgangsmåte for anvendelse av en optisk fiber som hydrostatisk trykkföler

摘要

A method is disclosed, for application of an optical fibre with a core (1) and a cladding (2) as a hydrostatic pressure sensor. A fibre-optic Bragg grating (5) is written into the core (1) of the optical fibre and two side-holes (3) are included in the cladding (2). Said side-hole optical fibre is spliced in-between standard single mode fibres (6), so that a change in differential pressure between the surroundings and the side-holes will cause a change in the fibre birefringence. This gives a change in wavelength separation between the two reflection peaks of the grating corresponding to each of the two orthogonal polarisation eigenmodes of the fibre, with an enhanced pressure sensitivity compared to the pressure included wavelength shift of a standard fibre grating. The side-hole fibre has a total birefrigence in the operating pressure range sufficient to split the two grating reflection, and such that the two peaks do not cross each other under operation.