Temperature Distribution Measurement Using Raman Ratio Thermometry

Abstract

A novel optical time domain reflectometry technique is described which uses the Raman Spectrum of backscattered light to give the temperature distribution along a conventional optical fibre. Temperatures from 77K to 800K can be measured.Spatial resolution is better than 3m, with sensor lengths of up to lkm.

A Review of Recent Developments in Fiber Optic Sensor Technology

“…Distributed sensing using the temperature dependence of Raman scattering was proposed and first demonstrated in the mid-1980s [90][91][92], and has since been developed into a commercial instrument by several companies, most notably York Technology. The Raman scattering process produces components in a broadband about the exciting (pump) wavelength comprising Stokes (lower photon energy) and anti-Stokes (higher photon energy) emissions as shown in Fig.…”

Improving the dynamic range in distributed anti-Stokes Raman thermometry by means of susceptibility asymmetry

“…Since experimental data are accompanied by uncertainty, the minimum anti-Stokes position are compatible with maximum Stokes position, moreover OTDR-like techniques have a precision length that in this case is about 40 m. It was found from figure 2, that the anti-Stokes Raman signal is serious deteriorated from the same point where Stokes signal reach its maximum. In a distributed thermometry sensor based on Raman scattering, the anti-Stokes amplitude is the fundamental parameter to be measured in order to determine the signal-noise ratio, dynamical range and also length precision 1 . In this way, we have performed some experiments to verify the impact of the anti-Stokes depletion in a distributed sensor operating in stimulated regime.…”

“…At room temperature most of the molecules are at the lower energy state, so anti-Stokes scattering is even rarer than Stokes. Since the scattered intensity is known one can determine the medium temperature by determining the anti-Stokes number of photons according to equation (1).…”

“…Since the first distributed sensor was developed 1,2 in 1985 many approaches has been discussed to manage the challenges in using Raman scattering as sensor mechanism 3 . It has also been done some efforts in order to increase spatial resolution in small sensors as well as to increase the sensing range at the same time that sensor´s accuracy is improved 4 at long distance applications.…”

A Novel Multifunctional Distributed Optical Fiber Sensor Based on Attenuation

“…One of the typical applications is the fault location in optical fiber communications [6]. Furthermore, Raman OTDR, Brillouin OTDR and optical frequency-domain reflectometry (OFDR) are also developed for intrinsic distributed optical fiber sensors [7][8][9][10]. To quasi-distributed optical fiber sensors, fiber bragg gratings (FBG) sensors are commercially manufactured for its unique features including high sensitivity, high multiplexing capability and cost-effectiveness.…”