A method and a system for interrogating an optical fiber includes a probe signal that has a first frequency comb at a first repetition rate (Δf) injected into the optical fiber. A backscattering signal that includes the probe signal convolved with an impulse response of the optical fiber in reflection which is sensitive to at least one parameter being measured from the optical fiber is gathered. The backscattering signal is beaten with a local oscillator signal to generate a beating signal, the local oscillator signal including a second frequency comb at a second repetition rate that is offset from the first repetition rate (Δf+δf) and being mutually coherent with the first frequency comb. The resulting beating signal is analysed to thereby determine the at least one parameter being measured from the optical fiber.

The present invention discloses a device for measuring gas temperature in plasma, including: a vacuum chamber, a fiber optic temperature sensor, a quartz tube, a circulator, a spectrometer, a broadband light source and a computer. One end of the quartz tube is inserted into the vacuum chamber. The fiber optic temperature sensor is located in the plasma in the vacuum chamber and fixed to the quartz tube. The fiber optic temperature sensor is connected to the circulator by means of an optical fiber passing through the quartz tube. The circulator is connected to the broadband light source and the spectrometer through optical fibers, respectively. The spectrometer is electrically connected to the computer which is configured to read and record spectra collected by the spectrometer.

The present invention discloses a device for measuring gas temperature in plasma, including: a vacuum chamber, a fiber optic temperature sensor, a quartz tube, a circulator, a spectrometer, a broadband light source and a computer. One end of the quartz tube is inserted into the vacuum chamber. The fiber optic temperature sensor is located in the plasma in the vacuum chamber and fixed to the quartz tube. The fiber optic temperature sensor is connected to the circulator by means of an optical fiber passing through the quartz tube. The circulator is connected to the broadband light source and the spectrometer through optical fibers, respectively. The spectrometer is electrically connected to the computer which is configured to read and record spectra collected by the spectrometer.

A device for coupling a sensor to a fiber optic cable including at least one optical fiber, the device may include an activation unit couplable to a known coupling location along the fiber optic cable and configured to: receive an analog sensor output signal from the sensor and change one or more properties of at least one of: one or more optical wave propagating through the at least one optical fiber and the at least one optical fiber, with respect to the analog output signal, while maintaining at least a portion of a spectral content of the analog sensor output signal during at least a portion of time.

A device for coupling a sensor to a fiber optic cable including at least one optical fiber, the device may include an activation unit couplable to a known coupling location along the fiber optic cable and configured to: receive an analog sensor output signal from the sensor and change one or more properties of at least one of: one or more optical wave propagating through the at least one optical fiber and the at least one optical fiber, with respect to the analog output signal, while maintaining at least a portion of a spectral content of the analog sensor output signal during at least a portion of time.

A method of detecting removal of a maintenance hatch includes transmitting an optical pulse along an optical fiber, wherein a first portion of the optical fiber is proximate to the maintenance hatch. The method further includes detecting backscatter light from the optical fiber using a sensor. The method further includes determining information related to the first portion of the optical fiber based on a comparison of the detected backscatter light and a trained model. The method further includes identifying whether the maintenance hatch has been removed based on the determined information.

A method of detecting one or more events comprises determining a plurality of temperature features from a temperature sensing signal, using the plurality of temperature features in an event detection model, and determining the presence or absence of the one or more events at one or more locations based on an output from the event detection model.

A method of detecting one or more events comprises determining a plurality of temperature features from a temperature sensing signal, using the plurality of temperature features in an event detection model, and determining the presence or absence of the one or more events at one or more locations based on an output from the event detection model.

Systems and methods consistent with the present disclosure may position a cementing tool within a casing string of a wellbore. Such a system may include a fiber optic cable coupled to the cementing tool and may include a distributed temperature sensing (DTS) system interrogator positionable at a surface of the wellbore for transmitting an optical signal through the fiber optic cable such that a plurality of temperatures along the fiber optic cable may be identified. A reel may be used when dispensing the fiber optic cable from a first end of the fiber optic cable in response to a tension in the fiber optic cable as the cementing tool travels down the casing string behind a cement composition. A processor in communication with the DTS system may be configured to monitor the plurality of temperatures along the fiber optic cable while the cement composition cures.

Sensing methods and systems for transformers, and the construction thereof, are described herein. Example transformer systems and example methods for constructing a core for the system are disclosed. The example system includes a core with a bottom plate, two or more limbs mounted to the bottom plate and a top plate enclosing the core. At least one of the bottom plate, the limbs and the top plate is formed with a sensing component therein. The sensing component can be mounted to a spacer layer assembled within a stack of laminated layers. The sensing component can be mounted within a path defined within the spacer layer, for example. Methods for detecting operating conditions within the transformer are also disclosed.