Abstract: A fiber optic distributed vibration system for detecting seismic signals in an earth formation is provided. The system includes a fiber optic cable deployed in a borehole that extends into the earth formation and which is configured to react along its length to a seismic wave incident on the fiber optic cable from outside the borehole. An optical source launches an optical signal into the fiber optic cable while the seismic wave is incident thereon. A receiver detects coherent Rayleigh noise (CRN) produced in response to the optical signal. A processing circuit processes the detected CRN signal to determine characteristics of the earth formation.

Abstract: A fiber optic cable includes a strain element including a first optical fiber and an optical element including a second optical fiber. The optical element is compliantly coupled with the strain element to transfer a portion of strain experienced by the strain element to the optical element. A fiber optic cable includes a strain transfer member, a central optical fiber disposed through the strain transfer member, and a tight jacket mechanically coupling the central optical fiber and the strain transfer member. The fiber optic cable further includes a compliant layer disposed about and affixed to the strain transfer member; a peripheral optical fiber disposed in the compliant layer, such that a portion of the strain experienced by the strain transfer member is transferred to the peripheral optical fiber via the compliant layer; and a protective cover disposed about the compliant layer.

Abstract: Methods and apparatus for measuring Brillouin backscattering from an optical fiber. A pulse of light with a first frequency is launched into an optical fiber. Backscattered light is received from the fiber, which includes Brillouin spectral line at a second frequency shifted from the first. The Brillouin spectral line varies with time and distance along the fiber. A signal representative of the backscattered light is obtained. The signal is divided into several components, each with a different frequency. The components are further treated, and one or more properties of the Brillouin spectral line are determined.

Abstract: A technique facilitates the monitoring of elongate structures. An elongate structure is combined with an optical fiber deployed along the structure. An interrogation system is operatively joined with the optical fiber to input and monitor optical signals to determine any changes in parameters related to the structure.

Abstract: A tilt meter includes a housing structure defining an inner chamber sealed from an environment outside the housing structure. First and second optical fiber sections are provided in the inner chamber. The second optical fiber section is optically coupled to the first optical fiber section, with the second optical fiber section rotated azimuthally with respect to the first optical fiber section. The first and second optical fiber sections are arranged to receive light transmitted from a remote light source, and a tilt of the housing structure induces a differential pressure within the inner chamber to be detected by the first and second optical fiber sections.

Abstract: An optical sensor array includes a plurality of interferometric sensors that are disposed at a plurality of locations in a region of interest. To determine a physical parameter at the plurality of locations, the array is interrogated with a plurality of optical pulses covering a range of optical wavelengths. The signals returned in response to the interrogating pulses are analyzed to determine an optical path imbalance associated with each sensor, where the optical path imbalance bears a relationship to the physical parameter of interest. Each sensor's contribution to the returned signals is determined by measuring the transit time between the launching of the interrogating pulses and the detection of the returned signals. By determining each sensor's contribution, the physical parameter may be determined at each of the plurality of locations.

Abstract: This disclosure relates in general to a method and system for acoustic monitoring using a fibre optic cable. More specifically, but not by way of limitation, embodiments of the present invention provide for using an optical fiber as a distributed interferometer that may be used to monitor a conduit, wellbore or reservoir. In certain aspects, the distributed interferometric monitoring provides for accurate detection of acoustic occurrences along the fibre optic cable and these acoustic occurrences may include fluid flow in a pipeline or wellbore, processes taking place in a wellbore or pipeline, fracturing, gravel packing, production logging and/or the like.

Abstract: Subterranean oilfield high-temperature devices configured or designed to facilitate downhole monitoring and high data transmission rates with remotely pumped lasers that are configured for operation downhole, within a borehole, at temperatures in excess of 115 degrees Celsius.

Abstract: A Brillouin laser having a narrowed linewidth, reduced relative intensity noise, and increased output power includes a pump laser that provides pump energy to an optical fiber resonant cavity to stimulate Brillouin emission. The output of pump laser is stabilized and its linewidth is narrowed by locking the frequency and phase of the optical signal generated by the pump laser to a longitudinal mode of the optical fiber resonant cavity. In addition, the resonant cavity is temperature and/or strain-tuned so that the Brillouin gain is substantially centered on a longitudinal mode of the cavity, thereby ensuring that the Brillouin frequency shift is substantially equal to an integer number of the free spectral range of the cavity.

Abstract: Acoustic monitoring of a conduit, a wellbore or a reservoir associated with hydrocarbon production or transportation and/or carbon dioxide sequestration is carried out using a fibre optic cable extending along or appurtenant to it as a distributed interferometer. Coherent Raleigh noise generated by the transmission of the coherent beam of radiation through the fiber optic is detected and processed to identify an acoustic occurrence.

Abstract: An improved laser source for use in a distributed temperature sensing (DTS) system (and DTS systems employing the same) includes a laser device and drive circuitry that cooperate to emit an optical pulse train at a characteristic wavelength between 1050 nm and 1090 nm. An optical amplifier, which is operably coupled to the laser device, is adapted to amplify the optical pulse train for output over the optical fiber sensor of the DTS system. In the preferred embodiment, the laser device operates at 1064 nm and outputs the optical pulse train via an optical fiber pigtail that is integral to its housing. The optical power of the optical pulse train generated by the laser source is greater than 100 mW, and preferably greater than 1 W, at a preferred pulse repetition frequency range between 1 and 50 kHz, and at a preferred pulse width range between 2 and 100 ns.

Abstract: A frequency-scanned optical time domain reflectometry technique includes launching a plurality of interrogating pulses into an optical fiber at a plurality of optical carrier frequencies. A Rayleigh backscatter signal is detected for each interrogating pulse as a function of time between the launching of the pulse and the detection of the backscatter signal. The time resolved Rayleigh backscatter signal at each optical frequency may then be examined to determine a distribution of a physical parameter along the length of the optical fiber.

Abstract: The present invention comprises a system and methods to actuate downhole tools by transmitting an optical signal through an optical fiber to the downhole tool. The optical signal can comprise a specific optical signal frequency, signal, wavelength or intensity. The downhole tool can comprise packers, perforating guns, flow control valves, such as sleeve valves and ball valves, samplers, sensors, pumps, screens (such as to expand), chemical cutters, plugs, detonators, or nipples.

Abstract: A distributed vibration sensor is positioned in a wellbore to measure fluid flow. The output of the sensor is monitored to acquire a distribution of vibration along a region of interest in the wellbore. An indication of the effectiveness of a well treatment to stimulate fluid flow in the wellbore may be provided based on the acquired vibration distribution. In some embodiments, the well treatment may be adjusted based on the indication of effectiveness.

Abstract: A method for measuring Brillouin backscattering comprises obtaining a signal representative of backscattered Brillouin light received from a deployed optical fibre, and dividing the signal into a plurality of signal components each having a different frequency hand. Each signal component is delivered to one of a plurality of parallel detection channels, in which the components are detected, and the signal generated by the detection is sampled using an analog-to-digital converter. The samples are then processed to determine one or more properties of the Brillouin spectral line. Detection may be optical, where the backscattered light is dispersed into a plurality of optical frequency components, or electrical, where the backscattered light is first frequency mixed to downconvert the frequency to the microwave regime.

Abstract: An intrusion detection system for monitoring a premises includes at least one optical cable that houses at least one optical fiber and extends about the premises. Optical time domain reflectometry (OTDR) means is operably coupled to opposite first and second ends of the at least one optical fiber. The OTDR means includes first signal processing circuitry that analyzes the backscatter signal received via the first end of the at least one optical fiber in order to detect an intrusion of the premises, and second signal processing circuitry that analyzes the backscatter signal received via the second end of the at least one optical fiber in order to detect an intrusion of the premises. The redundancy of intrusions decisions made by the first and second signal processing circuitry can be verified.

Abstract: A distributed acoustic wave detection system and method is provided. The system may include a fiber optic cable deployed in a well and configured to react to pressure changes resulting from a propagating acoustic wave and an optical source configured to launch interrogating pulses into the fiber optic cable. In addition, the system may include a receiver configured to detect coherent Rayleigh noise produced in response to the interrogating pulses. The CRN signal may be use to track the propagation of the acoustic wave in the well.

Abstract: To provide a polarization-diverse, heterodyne optical receiving system, a light signal is transmitted into an optical fiber having a plurality of optical sensors that are distinguishable using a multiplexing arrangement. A return light signal from the optical fiber is mixed with an optical local oscillator light signal, where the mixing outputs plural output signal portions having different polarizations. A birefringence of a particular optical sensor is determined based on the plural signal portions.

Abstract: An optical sensor array includes a plurality of interferometric sensors that are disposed at a plurality of locations in a region of interest. To determine a physical parameter at the plurality of locations, the array is interrogated with a plurality of optical pulses covering a range of optical wavelengths. The signals returned in response to the interrogating pulses are analyzed to determine an optical path imbalance associated with each sensor, where the optical path imbalance bears a relationship to the physical parameter of interest. Each sensor's contribution to the returned signals is determined by measuring the transit time between the launching of the interrogating pulses and the detection of the returned signals. By determining each sensor's contribution, the physical parameter may be determined at each of the plurality of locations.

Abstract: An optical time domain reflectometry (OTDR) system is configured to detect Rayleigh backscatter reflected from a multimode sensing optical fiber. The system includes a single spatial mode filtering system to select a single speckle of the Rayleigh backscatter produced in response to an optical pulse launched into the multimode fiber. The detected single speckle may be used for distributed disturbance (vibration) detection.