The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 11, 1999
Filed:
Jul. 05, 1996
British Telecommunications public limited company, London, GB;
Abstract
A substance sensor comprises a single-mode optical fibre having a core and a cladding having a lower refractive index than that of the core. A sensor material extends within the cladding towards the core. A layer of cladding is left between the sensor material and the core. The thickness (t) of the layer is sufficiently small that the sensor material lies within the evanescent wave which occurs within the cladding when optical radiation is conducted through the core. The refractive index of the sensor material varies in the presence of a substance to be sensed over a range which extends above and below the refractive index of the cladding. When its refractive index is lower than that of the cladding the sensor material operates, as far as the radiation is concerned, similarly to the cladding. However, when the refractive index of the sensor material is higher than that of the cladding the sensor material couples out some of the radiation, thereby reducing the transmissivity of the fibre. The sensor material may be, for example, polyethylene oxide, in which case the arrangement operates as a humidity sensor.