IMPROVEMENTS IN FIBRE OPTIC DISTRIBUTED SENSING

This application describes method and apparatus for fiber optic distributed acoustic sensing (DAS) that allow for quantitative estimation of relatively large and continuous stimuli acting on the sensing fiber. An optical fiber (101) is interrogated with optical pulse and the Rayleigh backscatter det...

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Bibliographische Detailangaben
Hauptverfasser:	ALASTAIR, GODFREY, ROGER IAN, CRICKMORE
Format:	Patent
Sprache:	eng ; fre ; ger
Schlagworte:	ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVEREDIN A SINGLE OTHER SUBCLASS MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC ORINFRASONIC WAVES MEASURING MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR PHYSICS TARIFF METERING APPARATUS TESTING
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Beschreibung
Zusammenfassung:	This application describes method and apparatus for fiber optic distributed acoustic sensing (DAS) that allow for quantitative estimation of relatively large and continuous stimuli acting on the sensing fiber. An optical fiber (101) is interrogated with optical pulse and the Rayleigh backscatter detected to provide a DAS sensor. The method involves identifying a first stimulus acting on at least one sensing portion of the optical fiber, which results in an effective optical path length change within said sensing portion of at least the wavelength of the optical radiation. Such a path length change will result in signal wrapping leading to an observed variation (401) in backscatter intensity. The frequency of variation is detected and can be used to estimate the rate of change of path length. The method can be used to estimate strain rate and/or rate of change of temperature.