Distributed sensing apparatus

摘要

Apparatus for sensing temperature or strain in an optical sensing fibre 6 comprises a laser 1; first means 3 for modifying light from the laser by a Brillouin frequency shift; second means 7 for converting light from the laser into pulses. Modified light from the first and second means is directed to the first and second ends of the sensing fibre 6. Light entering the fibre 6 from the respective two ends interacts to amplify the light entering from the first fibre end by a Brillouin gain or reduce its power by a Brillouin loss, which can be measured to give an indication of temperature or strain in the fibre. Further embodiments include threshold temperature and strain sensing, means for transmitting communications signals along the fibre and enhanced sensing utilising a second sensing fibre.