Abstract: A distributed measurement system includes a first distributed optical sensing fiber deployed along a first desired measurement path and a second distributed optical sensing fiber deployed along a second desired measurement path. The system further includes an interrogation system coupled to the first distributed optical sensing fiber and to the second distributed optical sensing fiber. The system also includes a first distributed measuring instrument launch a first interrogating probe pulse set comprising a first pulse having a first frequency and a second pulse having a second frequency. The interrogation system is designed to direct the first pulse to the first distributed optical sensing fiber and the second pulse to the second distributed optical sensing fiber.

Abstract: A distributed measurement system includes a first distributed optical sensing fiber deployed along a first desired measurement path and a second distributed optical sensing fiber deployed along a second desired measurement path. The system further includes an interrogation system coupled to the first distributed optical sensing fiber and to the second distributed optical sensing fiber. The system also includes a first distributed measuring instrument launch a first interrogating probe pulse set comprising a first pulse having a first frequency and a second pulse having a second frequency. The interrogation system is designed to direct the first pulse to the first distributed optical sensing fiber and the second pulse to the second distributed optical sensing fiber.

Abstract: An optical-fiber-containing sensor wire with at least one hermetically sealed optical fiber are provided. An optical-fiber-containing sensor wire may be installed in a cable that can be placed downhole in a wellbore. The optical-fiber-containing sensor wire may include a first optical fiber hermetically sealed within a metallic structure of the optical-fiber-containing sensor wire.

Abstract: A technique facilitates the use and application of a distributed vibration sensing system in, for example, a well application. The technique enables selection of a desired gauge length to achieve an optimum trade-off between the spatial resolution of a distributed vibration sensing/distributed acoustic sensing system and signal-to-noise ratio. The optimum gauge length can vary according to specific factors, e.g. depth within a well, and the present technique can be used to account for such factors in selecting an optimal gauge length which facilitates accurate collection of data on dynamic strain.

Abstract: Techniques are disclosed that facilitate use of a distributed vibration sensing system for collecting data in a well application to provide improved collection of strain related data, such as for a seismic survey. The techniques facilitate selection of a variable optimal gauge length that optimally preserves the signal bandwidth and temporal resolution of the sensing system and that can be tuned using the actual apparent velocity and maximum recoverable frequency of the monitored parameters. Techniques for real-time processing of DVS data using a preliminary variable optimal gauge length are disclosed, as well as techniques for re-processing the DVS data at a later time using an updated variable optimal gauge length that is derived from the preliminary processing of the DVS data.

Abstract: An optical-fiber-containing sensor wire with at least one hermetically sealed optical fiber are provided. An optical-fiber-containing sensor wire may be installed in a cable that can be placed downhole in a wellbore. The optical-fiber-containing sensor wire may include a first optical fiber hermetically sealed within a metallic structure of the optical-fiber-containing sensor wire.

Abstract: A system and method for simultaneously addressing multiple parallel distributed fiber optic sensors using a single interrogation instrument is disclosed. One or more of the fiber optic sensors are provided with a non-reflective delay element to prevent an overlap in time between backscatter returns from the distributed fiber optic sensors, thereby allowing the backscatter returns from each sensor to be distinguished based on round-trip transit time.

Abstract: A system and method for simultaneously addressing multiple parallel distributed fiber optic sensors using a single interrogation instrument is disclosed. One or more of the fiber optic sensors are provided with a non-reflective delay element to prevent an overlap in time between backscatter returns from the distributed fiber optic sensors, thereby allowing the backscatter returns from each sensor to be distinguished based on round-trip transit time.

Abstract: Methods for determining separate velocity components of an acoustic wavefield that are incident on a distributed fiber optic sensor are disclosed. A fiber optic sensor includes fiber that is spatially distributed in non-parallel planes of a three-dimensional volume having three orthogonal axes. The fiber includes a first fiber pattern that is spatially distributed within a first plane of the three-dimensional volume, and a second fiber pattern that is spatially distributed within a second plane of the volume. The fiber patterns are interrogated separately by a distributed fiber optic interrogation system. The individual responses from each pattern are combined and processed to determine separate velocity components of the acoustic wavefield relative to the orthogonal axes of the three-dimensional volume.

Abstract: An apparatus and method for correcting the wavenumber sensitivity of a distributed fiber optic sensor are disclosed. The distributed fiber optic sensor is deployed in a region of interest to measure a characteristic of an incident acoustic wavefield. A composite response of the distributed sensor is determined based on backscatter optical signals generated by the sensor, where the composite response is indicative of a characteristic of an incident acoustic wavefield. The composite response includes at least a first response having a first wavenumber sensitivity and a second response having a second wavenumber sensitivity. The second wavenumber sensitivity is selected so that wavenumber notches of the first and second responses do not overlap.

Abstract: A technique facilitates the use and application of a distributed vibration sensing system in, for example, a well application. The technique enables selection of a desired gauge length to achieve an optimum trade-off between the spatial resolution of a distributed vibration sensing/distributed acoustic sensing system and signal-to-noise ratio. The optimum gauge length can vary according to specific factors, e.g. depth within a well, and the present technique can be used to account for such factors in selecting an optimal gauge length which facilitates accurate collection of data on dynamic strain.

Abstract: 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.

Abstract: Apparatus and a method for monitoring of a pipe inspection tool in a pipeline, the apparatus comprising at least one sensor carrier apparatus being locatable along and in close proximity to a pipeline, a plurality of acoustic sensors being locatable on the sensor carrier apparatus, a pipeline inspection tool which is moveable through the pipeline being detectable by means of the acoustic sensors, and the location of the pipeline inspection tool being able to be determined by means of the acoustic sensors.

Abstract: Apparatus and a method for monitoring of a pipe inspection tool in a pipeline, the apparatus comprising at least one sensor carrier apparatus being locatable along and in close proximity to a pipeline, a plurality of acoustic sensors being locatable on the sensor carrier apparatus, a pipeline inspection tool which is moveable through the pipeline being detectable by means of the acoustic sensors, and the location of the pipeline inspection tool being able to be determined by means of the acoustic sensors.

Abstract: A fiber optic sensing system includes a fiber optic sensor having a plurality of densely spaced, non-naturally occurring discrete reflectors having a weak reflectivity of less than 1% and, in some cases, even less than 0.0001% depending on the density of the reflectors. The fiber optic sensor is configured so that the spatial resolution of the backscattered signal generated in response to a probe signal is greater than the separation between at least two discrete reflectors, so that backscatter generated by the at least two reflectors overlaps at the receiver. Data representative of a parameter of interest, such as temperature or strain, can be acquired from the detected backscatter and processed in order to provide information about conditions in a region of interest.

Abstract: An apparatus and method for correcting the wavenumber sensitivity of a distributed fiber optic sensor are disclosed. The distributed fiber optic sensor is deployed in a region of interest to measure a characteristic of an incident acoustic wavefield. A composite response of the distributed sensor is determined based on backscatter optical signals generated by the sensor, where the composite response is indicative of a characteristic of an incident acoustic wavefield. The composite response includes at least a first response having a first wavenumber sensitivity and a second response having a second wavenumber sensitivity. The second wavenumber sensitivity is selected so that wavenumber notches of the first and second responses do not overlap.

Abstract: Methods for determining separate velocity components of an acoustic wavefield that are incident on a distributed fiber optic sensor are disclosed. A fiber optic sensor includes fiber that is spatially distributed in non-parallel planes of a three-dimensional volume having three orthogonal axes. The fiber includes a first fiber pattern that is spatially distributed within a first plane of the three-dimensional volume, and a second fiber pattern that is spatially distributed within a second plane of the volume. The fiber patterns are interrogated separately by a distributed fiber optic interrogation system. The individual responses from each pattern are combined and processed to determine separate velocity components of the acoustic wavefield relative to the orthogonal axes of the three-dimensional volume.

Abstract: 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.

Abstract: 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.

Abstract: An optical fiber tape assembly for attaching an optical fiber to the surface of a pipe comprising; at least one optical fiber; and a tape having an attachment means to enable attachment of the tape to the pipe; wherein the optical fiber runs longitudinal along the tape and is integral with the tape.