US 12,411,026 B2
Fibre optic sensing
Roger Crickmore, Farnborough (GB)
Assigned to Optasense Holdings Limited, Camberley (GB)
Appl. No. 18/027,685
Filed by Optasense Holdings Limited, Farnborough (GB)
PCT Filed Dec. 14, 2021, PCT No. PCT/GB2021/053269
§ 371(c)(1), (2) Date Mar. 22, 2023,
PCT Pub. No. WO2022/136832, PCT Pub. Date Jun. 30, 2022.
Claims priority of application No. 2020409 (GB), filed on Dec. 22, 2020.
Prior Publication US 2023/0375378 A1, Nov. 23, 2023
Int. Cl. G01D 5/353 (2006.01); H04B 10/079 (2013.01)
CPC G01D 5/35361 (2013.01) [H04B 10/0791 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A distributed fibre optic sensing apparatus, comprising:
an interrogator for repeatedly interrogating a sensing optical fibre with interrogating optical radiation and detecting radiation which is Rayleigh backscattered from within the sensing fibre,
wherein the sensing apparatus is operable in a first mode of operation, in which:
the interrogator is optically coupled to the sensing fibre so that interrogating radiation output from the interrogator is transmitted to the sensing fibre via a first optical system that comprises a first length of optical fibre upstream of a first polariser;
the interrogator is configured to output coherent optical radiation with an optical power such that the interrogating radiation experiences non-linear effects when propagating in the first length of optical fibre so as to reduce coherence of the interrogating radiation; and
the interrogator is configured to determine the extent of any variation in polarisation of the radiation which is Rayleigh backscattered from within the sensing fibre.