摘要:
A device to measure a fluid pressure comprises a pressure sensing element 10 and a pressure readout element 20. The pressure sensing element 10 comprises a cavity 11 capped by a flexible membrane 13, the cavity having a length d that varies with the fluid pressure P1 applied on the flexible membrane 13. The pressure readout element 20 comprises a light source 24 for providing an incident beam of a determined wavelength range directed towards the cavity and an optical spectral analyzer 25 for measuring a power spectrum of a return beam reflected by the cavity, and processing means 27 for determining the cavity length d and the fluid pressure P1 based on the power spectrum.
摘要:
A device to measure a fluid pressure comprises a pressure sensing element 10 and a pressure readout element 20. The pressure sensing element 10 comprises a cavity 11 capped by a flexible membrane 13, the cavity having a length d that varies with the fluid pressure P1 applied on the flexible membrane 13. The pressure readout element 20 comprises a light source 24 for providing an incident beam of a determined wavelength range directed towards the cavity and an optical spectral analyzer 25 for measuring a power spectrum of a return beam reflected by the cavity, and processing means 27 for determining the cavity length d and the fluid pressure P1 based on the power spectrum.
摘要:
A telemetry apparatus and method for communicating data from a down-hole location through a borehole to the surface is described including a light source, an optical fiber being placed along the length of the wellbore and receiving light from the light source, a transducer located such as to produce a force field (e.g. a magnetic field) across the optical fiber and its protective hull without mechanical penetration of the hull at the down-hole location, one or more sensors for measuring down-hole conditions and/or parameters, a controller to provide a modulated signal to the magnetic field generator, said modulated signal being under operating conditions representative of measurements by the one or more sensors, and an optical detector adapted to detect changes in the light intensity or polarization of light passing through the fiber.
摘要:
An optical fiber sensor system and method for monitoring a condition of a linear structure such as a pipeline is provided which is capable of providing continuous monitoring in the event of a break in the sensing optical fiber or fibers. The system includes at least one sensing fiber provided along the length of the linear structure, and first and second interrogation and laser pumping sub-systems disposed at opposite ends of the sensing fiber, each of which includes a reflectometer. The reflectometer of the first interrogation and laser pumping sub-system is connected to one end of the sensing fiber. The reflectometer of the second interrogation and laser pumping sub-system is coupled to either (i) an end of a second sensing fiber provided along the length of the linear structure which is opposite from the one end of the first sensing fiber, or (ii) the opposite end of the first sensing fiber. Before any break of the sensing fiber or fibers occurs, each reflectometer redundantly monitors the condition of the linear structure over its entire length. After any such break occurs, each reflectometer will continue to receive signals up to the point of the break from opposite ends of the structure.
摘要:
A method of obtaining a distributed measurement comprises deploying an optical fibre in a measurement region of interest, and launching into it a first optical signal at a first wavelength λ0 and a high power level, a second optical signal at a second wavelength λ−1, and a third optical signal at the first wavelength λ0 and a low power level. These optical signals generate backscattered light at the second wavelength λ−1 arising from Raman scattering of the first optical signal which is indicative of a parameter to be measured, at the first wavelength λ0 arising from Rayleigh scattering of the first optical signal, at the second wavelength λ−1 arising from Rayleigh scattering of the second optical signal, and at the first wavelength λ0 arising from Rayleigh scattering of the third optical signal. The backscattered light is detected to generate four output signals, and a final output signal is derived by normalising the Raman scattering signal to a function derived from the three Rayleigh scattering signals, which removes the effects of wavelength-dependent and nonlinear loss.
摘要:
A technique includes providing an optical source signal to an optical fiber to produce a backscatter signal. A receiver is provided to detect the backscatter signal. During an acquisition period in which the backscatter signal is present, a sensitivity of the receiver is varied with respect to time to regulate an input signal range of an amplifier of the receiver.
摘要:
A method of measuring a selected physical parameter at a location within a region of interest comprises the steps of: launching optical pulses at a plurality of reselected interrogation wavelengths into an optical fibber (1) deployed along the region of interest, reflectors (20,21,2n) being arrayed along the optical fibber (1) to form an array (9) of sensor elements, the optical path length between the said reflectors (2) being dependent upon the selected parameter; detecting the returned optical interference signal for each of the reselected wavelengths; and determining from the optical interference signal the absolute optical path length (L) between two reflectors (2) at the said location, and from the optical path length (L) so determined the value of the selected parameter at the said location; wherein the step of determining the absolute optical path length (L) comprises carrying out a process in which the phase difference between the interference signals for a pair of the reselected wavelengths is estimated using an estimated value for the optical path length (L), the estimated phase difference is used to estimate the phase at each of those wavelengths, and the phase thus obtained is used to revise the estimated value for the optical path length (L), the process being repeated for some or all remaining wavelength pairs in sequence, on the basis of the optical path length (L) estimated for the immediately preceding pair in the sequence, thereby to progressively revise the optical path length (L) until it is know to a desired level of accuracy.
摘要:
The invention is an optical fiber distributed temperature sensing system comprising an opto-electronic unit and a sensing optical fiber, which system measures temperature so as to provide a temperature profile along at least part of the length of the optical fiber. The system includes reference coils, which are temperature reference points, at a location that is remote from the opto-electronic unit and closer to the region whose temperature is being measured.
摘要:
A system to determine the mixture of fluids in the deviated section of a wellbore comprising at least one distributed temperature sensor adapted to measure the temperature profile along at least two levels of a vertical axis of the deviated section. Each distributed temperature sensor can be a fiber optic line functionally connected to a light source that may utilize optical time domain reflectometry to measure the temperature profile along the length of the fiber line. The temperature profiles at different positions along the vertical axis of the deviated wellbore enables the determination of the cross-sectional distribution of fluids flowing along the deviated section. Together with the fluid velocity of each of the fluids flowing along the deviated section, the cross-sectional fluid distribution enables the calculation of the flow rates of each of the fluids. The system may also be used in conjunction with a pipeline, such as a subsea pipeline, to determine the flow rates of fluids flowing therethrough.
摘要:
A fiber optic sensor system includes an optical source to output a first optical signal to launch into an optical fiber, and a coherent detector to mix a coherent Rayleigh backscatter signal generated by the optical fiber in response to the first optical signal with a second optical signal output by the optical source and to generate a mixed output signal. A phase detection and acquisition system determines a phase difference between first and second locations along the optical fiber based on phase information extracted from the mixed output signal and combines the phase information extracted from multiple acquisitions to detect strain on the optical fiber sensor.