Fibre Optic Sensing

Abstract

A fibre optic sensing apparatus (400) is described which has an optical output path (403, 405, 404) configured to repeatedly interrogate a sensing optical fibre (402) by launching coherent optical radiation into the sensing optical fibre. A detector (407) is configured to receive optical radiation that is Rayleigh backscattered from the sensing optical fibre and output a detected backscatter signal in response to each interrogation and a processor (408) processes the detected backscatter signal. The apparatus is operable in a frequency swept mode, in which the sensing optical fibre is interrogated with a first set of interrogations of coherent optical radiation having different optical frequencies from one another to acquire, for at least one sensing portion of the sensing optical fibre, a backscatter spectral profile (201) of a measurement value of the detected backscatter signal with frequency across a first frequency range. The processor is configured to combine a plurality of said backscatter spectral profiles (201, 202) to form a reference profile (203) with an effective frequency range greater than the first frequency range

Dependencies are inferred from the claim text.