A distributed temperature sensor is described that uses standard multi-modecommunications grade fibre as the intrinsic sensing element. The sensor employs anadaptation of optical time domain reflectometry (OTDR), a fibre analysis techniquewell established in the telecommunications industry. Spectral selection of the anti- stokes Raman side band provides a signal which is sensitive to temperature.A temperature profile is received along the entire length of an optical fibre whichmay be up to 10 km long. (A typical fibre length of 4 km would give 4000 pointsof information resolved to Ã‚Â±1Ã‚Â°C and updated every 15 seconds).Among the advantages of this approach are the ease of installation andmaintenance, immunity to electromagnetic interference (EMI), safety in hazardousenvironments and the provision of not only temperature but also position data.The applications for distributed temperature measurements are very broad ranging,for example, from monitoring curing conditions in concrete structures and powercable hot spot detection to energy management and fire protection. Theperformance specification is discussed and a system configuration is suggested.
P. R. Orrell,
"Fiber optic distributed temperature sensing", Proc. SPIE 1777, First European Conference on Smart Structures and Materials, 17770V (1 May 1992); doi: 10.1117/12.2298054; https://doi.org/10.1117/12.2298054