| 摘要 |
A pressure sensing apparatus 100 has a light source 102 for transmitting pulses of light along a monomode optical fibre 110. The polarisation of light backscattered from the light pulses in the optical fibre is detected by a polarisation processing unit (PPU) 104 and a photo detector 116. The optical fibre is adapted to deform asymmetrically under the influence of applied external isotropic pressure such as from a fluid (e.g. it may be a side-hole fibre). The deformation causes the birefringence of the optical fibre to change proportionally to the applied pressure. The change in birefringence can be determined from the detected polarisation of the backscattered light, allowing detection of pressure distribution in the fluid. Importantly, the construction of the optical fibre is such that the birefringence beat length of the optical fibre at the wavelength of light propagated by the fibre remains more than twice the spatial length of the light pulses transmitted along the optical fibre (i.e. the fibre has low birefringence). Applications of the invention include detection of fluid flow, location of an interface between two fluids of different density and tsunami detection. |
