Abstract:
Methods and apparatus for performing Distributed Acoustic Sensing (DAS) using fiber optics with increased acoustic sensitivity are provided. Acoustic sensing of a wellbore, pipeline, or other conduit/tube based on DAS may have increased acoustic sensitivity through fiber optic cable design and/or increasing the Rayleigh backscatter property of a fiber's optical core. Some embodiments may utilize a resonant sensor mechanism with a high Q coupled to the DAS device for increased acoustic sensitivity.
Abstract:
Method and apparatus enable optical evanescent sensing utilizing a waveguide with an annular core. The annular core can provide detectable sensitivity to a measurand due to optical interactions with contents along an inside surface of the annular core since optical properties of the contents vary with changes in the measurand.
Abstract:
Methods and apparatus for the active control of a wavelength-swept light source used to interrogate optical elements having characteristic wavelengths distributed across a wavelength range are provided.
Abstract:
Methods and apparatus for distributed temperature sensing (DTS) along a single mode or multimode optical waveguide or fiber include a calibration of initial Brillouin-based DTS measurements using Raman-based DTS measurements to enable accurate subsequent Brillouin-based DTS measurements. Such calibration may occur while the fiber is deployed in the environment in which temperature is to be sensed and thereby corrects influences on Brillouin scattered light from stress or strain along the fiber. Further, calibration may utilize one or more discrete temperature sensors to correct errors in one or both of the Brillouin-based DTS measurements and the Raman-based DTS measurements.
Abstract:
Methods and apparatus for distributed temperature sensing (DTS) along a single mode or multimode optical waveguide or fiber include a calibration of initial Brillouin-based DTS measurements using Raman-based DTS measurements to enable accurate subsequent Brillouin-based DTS measurements. Such calibration may occur while the fiber is deployed in the environment in which temperature is to be sensed and thereby corrects influences on Brillouin scattered light from stress or strain along the fiber. Further, calibration may utilize one or more discrete temperature sensors to correct errors in one or both of the Brillouin-based DTS measurements and the Raman-based DTS measurements.
Abstract:
Methods and apparatus enable monitoring conditions in a well-bore using multiple cane-based sensors. The apparatus includes an array of cane-based Bragg grating sensors located in a single conduit for use in the well-bore. For some embodiments, each sensor is located at a different linear location along the conduit allowing for increased monitoring locations along the conduit.
Abstract:
Methods and apparatus for sampling techniques can constantly monitor a spectral output from a broadband source in order to control a central wavelength of interrogation light supplied by the source for input to a sensor. A first portion of light output from the broadband source passes through a controller module for spectral analysis and referencing to provide measurements that can be used as feedback to actively modify a second portion of the light from the source. This modified second portion thereby controls the central wavelength to ensure accurate determination of sensor response signals received at a receiver.
Abstract:
Methods and apparatus for the active control of a wavelength-swept light source used to interrogate optical elements having characteristic wavelengths distributed across a wavelength range are provided.
Abstract:
Methods and apparatus for sampling techniques can constantly monitor a spectral output from a broadband source in order to control a central wavelength of interrogation light supplied by the source for input to a sensor. A first portion of light output from the broadband source passes through a controller module for spectral analysis and referencing to provide measurements that can be used as feedback to actively modify a second portion of the light from the source. This modified second portion thereby controls the central wavelength to ensure accurate determination of sensor response signals received at a receiver.
Abstract:
Methods and apparatus enable compensation of source light wavelength fluctuations due to instability of a broadband source within an optical sensing system. Tapping off two or more portions of the light output from the source at specific wavelength bands enables power based measurements of these portions. The measurements provide compensation ability by either use as feedback to control the source or for determination of the central wavelength so that adjustments can be applied to sensor response signals received at a receiver.