METHOD AND APPARATUS FOR INTERROGATING FIBER OPTIC SENSORS

WIPO Patent Application WO2002044659

A3

An apparatus and method for interrogating fiber optic sensors non-intrusively sensing fluid flow within a pipe includes a two beam interferometer which comprises an optics circuit for generating a series of discrete light pulses that are directed at sensors positioned between pairs of low reflectivity fiber Bragg gratings. The successive light pulses are split into first light pulses and second light pulses and the second light pulses are delayed a known time period relative to the first pulses. The first and second light pulses are combined onto a single optical fiber and directed through the low reflectivity gratings and the sensor positioned between the gratings. Reflected pulses from the series of pulses impinge on a photoreceiver and interrogator wherein the phase shift between the reflected first light pulses from the second grating and the reflected second light pulses from the first grating for each sensor are determined. Phase shifts from successive pulses for each sensor are compared and a change in a measured parameter of the fluid is determined.

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KERSEY ALAN D
DAVIS ALLEN R
FERNALD MARK R
WINSTON CHARLES R
BAILEY TIMOTHY J

PCT/GB2001/005293

September 12, 2002

November 29, 2001

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WEATHERFORD LAMB (US)
HARDING RICHARD PATRICK (GB)

G01D5/353; (IPC1-7): G01F1/66; G01L9/00; G01D5/353

WO2000000799A1

2000-01-06

US5218197A	1993-06-08
US5808779A	1998-09-15
US5513913A	1996-05-07

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