Patent ID: 7284903

Claim:
A method of using an optical fibre to obtain a distributed measurement of a parameter of interest, comprising: deploying an optical fibre in a measurement region of interest; launching a first optical signal at a first wavelength λ 0 and a first optical power level into the optical fibre; detecting backscattered light emitted from the optical fibre at a second wavelength λ −1 arising from inelastic scattering of the first optical signal, and generating a first output signal therefrom, the first output signal being indicative of the parameter of interest; detecting backscattered light emitted from the optical fibre at the first wavelength λ 0 arising from elastic scattering of the first optical signal, and generating a second output signal therefrom; launching a second optical signal at the second wavelength λ −1 into the optical fibre; detecting backscattered light emitted from the optical fibre at the second wavelength λ −1 arising from elastic scattering of the second optical signal, and generating a third output signal therefrom; launching a third optical signal at the first wavelength λ 0 and a second optical power level less than the first optical power level into the optical fibre; detecting backscattered light emitted from the optical fibre at the first wavelength λ 0 arising from elastic scattering of the third optical signal, and generating a fourth output signal therefrom; generating a synthetic output signal from the second output signal and the fourth output signal; and generating a final output signal indicative of the parameter of interest by normalising the first output signal to the geometric mean of the synthetic output signal and the third output signal.