Distributed temperature sensing system with fiber Bragg gratings
AssigneePrecise Downhole Services Ltd.
InventorsMichael Melnychuk, Daniel Keough, Aleksei Andriianov, Sean Begley
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Abstract
A system and method for calibrating a distributed temperature sensing (DTS) system having a fiber optic receiver coupled to an optical fiber, includes fiber Bragg gratings (FBGs) integrally formed within the optical fiber, and a processor configured to compute a temperature datum for a location of each FBG based on signals generated by the fiber optic receiver in response to light reflections from the FBG; and adjusting a computed temperature data profile along the optical fiber segment, based on the computed temperature datum for each location of an FBG.
Claims12
A method for calibrating a distributed temperature sensing (DTS) system comprising a fiber optic transmitter and receiver coupled to an optical fiber comprising a single mode (SM) fiber segment spliced to a multimode (MM) fiber segment, the method comprising the steps of:
- (a) providing a plurality of fiber Bragg gratings (FBGs) within the SM fiber segment of the optical fiber,
- wherein a nominal Bragg wavelength of one of the FBGs differs from a nominal Bragg wavelength of another one of the FBGs;
- (b) transmitting a light pulse into the optical fiber with the transmitter, and receiving backscattered light with the receiver;
- (c) using at least one processor for:
- (i) computing a DTS temperature data profile along a length of the optical fiber;
- (ii) determining a temperature datum for a location of each of the plurality of FBGs based on signals generated by the fiber optic receiver in response to light reflections from each FBG, wherein the determination comprises:
- analyzing each reflected signal to detect the associated Bragg wavelength;
- determining the FBG associated with each detected Bragg wavelength by identifying the FBG with a nominal Bragg wavelength that most closely matches the detected Bragg wavelength;
- comparing each detected Bragg wavelength to the nominal Bragg wavelength of the associated FBG to determine a corresponding wavelength shift;
- and
- determining the temperature datum at the predefined location of each FBG by applying an FBG-specific calibration model which relates the wavelength shift to a temperature;
- and
- iii) adjusting the DTS temperature data profile, based on the computed temperature datums for each location of each of the plurality of FBGs.
A system for calibrating a distributed temperature sensing (DTS) system comprising a fiber optic receiver coupled to an optical fiber comprising a single mode (SM) fiber segment spliced to a multimode (MM) fiber segment, the system comprising:
- (a) a plurality of fiber Bragg gratings (FBGs) integrally formed within the SM fiber segment of the optical fiber wherein a nominal Bragg wavelength of one of the FBGs differs from a nominal Bragg wavelength of another one of the FBGS;
- (b) at least one processor operatively connected to the fiber optic receiver, and a non-transient computer readable medium storing instructions executable by the at least one processor to implement a method comprising:
- (i) determining a temperature datum for a location of each of the plurality of FBGs based on signals generated by the fiber optic receiver in response to light reflections from each FBG, wherein the determination comprises:
- analyzing each reflected signal to detect the associated Bragg wavelength;
- determining the FBG associated with each detected Bragg wavelength by identifying the FBG with a nominal Bragg wavelength that most closely matches the detected wavelength;
- comparing each detected Brage wavelength to the nominal Bragg wavelength of the associated FBG to determine a corresponding wavelength shift;
- and
- determining the temperature datum at the predefined location of each FBG by applying an FBG-specific calibration model which relates the wavelength shift to a temperature;
- and
- (ii) adjusting a computed temperature data profile along the optical fiber segment, based on the computed temperature datum for the location of the one FBG.
Dependencies are inferred from the claim text.