Abstract: A fibre optic sensor deployed on a fibre optic cable to a remote location, such as an oil or gas well. The sensor, which can sense any of a variety of parameters such as pressure, temperature, flow rate, strain, or chemical properties, is located within a sleeve. The sleeve is constructed from a low-friction material, such as polytetrafluoroethylene, glass, or ceramic. Further, the sensor can float on a high-density fluid that surrounds it, or sink in a low-density fluid that surrounds it.

Abstract: A method, apparatus and system are disclosed for general use and for specific use when measuring pressure in well bores of hydrocarbon wells. A sensor, an interferometric optical pressure transducer 22, is disposed at the end if a fibre optic line 20 and illuminated by broadband light pulses from a pulsed broadband light source 10. Measuring equipment is provided, in the form of reflectors 31 and filters 34A 34B 34C producing modulated and temporally separate light pulses 36 38 40 36A 38A 40A which are measured by a common photodiode 30, whose output is supplied to a microprocessor 56 driving a display 60 which indicates the pressure applied to the sensor 22. The transducer 22 is mathematically modelled by subjecting the transducer 22 to known pressures and noting the outputs. The measuring equipment 30-34 is mathematically modelled by applying test signals and noting the response for each signal. The mathematical models are combined (with individual device compensating factors).

Abstract: A method and apparatus for receiving measurements from an interferometer transducer (22) uses a broad band light beam (19A), reflected from the transducer (22), and compares it with the amplitudes of narrow band beams, derived from the reflected broad band light beam (19A), by filters (23A-23D) on different frequencies. The narrow band light beams and the broad band light beam (19A) are measured on photo detectors (22A, 21B-21E). Microprocessor (57) compares outputs of the photo detectors to interpret phase differences between signals (25, 27, 29) from the narrow band beams. A periodically operable shutter and a single photo detector (21) can also be used. Other embodiments modulate (12) the light source (10) to produce very short broad band pulses of light (36, 40) which are reflected from the transducer (22).

Abstract: An apparatus for sensing data from a remote optical sensor 16 has its frequency stabilised by balancing the outputs of narrow band filter 28 30, spaced about a desired frequency 36 positioned at about the 3db down points 40 of a broad band light source 10 using voltage control, current control or temperature control to vary the frequency of the wide band light source 10. Difference between the outputs through the two narrow band filters 28 30 can be used to drive an amplifier 48 to correct the frequency of the broad band light source. The outputs through the two narrow band filters 28 30 can be converted 52 to binary numbers and fed to a microprocessor 56 which is used, via analog conversion 60, to drive the amplifier 48. The broad band light source 10 can be pulse modulated 68 to provide temporally separate light pulses 92 94 through each of the narrow band filters 28 30, measured at separate times.