FIBRE OPTIC SENSING SYSTEM

摘要

Method and apparatus for measuring physical parameters, wherein pulses of light (20, 25) are injected into opposite ends of a fibre optic cable (15) made from fluorescent material. The fluorescent material and wavelength of the photons (30, 35) is such that two photon absorption and fluorescence occurs through absorption of a photon (30, 35) from each pulse (20, 25). The fluoresced light (45) is then detected (50) and used to determine the value of a physical parameter such as temperature or strain. The timing of the injected pulses (20, 25) relative to each other may be varied in order to select measurement points along the fibre (15). The background fluoresced light signal may be reduced or eliminated by using pulses (20, 25) having differing frequencies and/or having a non-resonant pulse of considerably greater intensity than any resonant pulses.