A gauge apparatus includes a body member, one or more gauge arms biased outwardly from the body member for engagement with a wall of the elongated space, and one or more deformable regions. The gauge apparatus is configured so that a variation in an outward extension of each gauge arm from the body member induces a change in strain in a corresponding one of the one or more deformable regions. A gauge system includes the gauge apparatus and an optical fiber attached to the gauge apparatus so that a strain in each deformable region of the gauge apparatus is transferred to a corresponding sensor portion of the optical fiber. The gauge system may be used for making real-time measurements of a geometry of an elongated space such as a wellbore of an oil and gas well.

An embodiment of a system includes a light source, an optical assembly, and an electronic circuit. The light source (e.g., a laser) is configured to generate a source optical signal. The optical assembly is configured to direct the source optical signal into an end of an optical-fiber assembly that includes an optical fiber having a section wrapped multiple turns around a mandrel and including mandrel zones, and to receive, from the end of the optical-fiber assembly, a return optical signal. The electronic circuit is configured to select at least one mandrel zone in response to a component of the return optical signal from the at least one mandrel zone, and to detect an acoustic signal incident on the mandrel in response to the component of the return optical signal.

One example coherent optical time domain reflectometer device includes a coherent light source that produces coherent probe light pulses at an optical wavelength; an optical coupling unit coupled to f a fiber link under test to direct the coherent probe light pulses into the fiber link and to receive reflected probe light pulses from the fiber link; an optical detection unit to receive the reflected probe light pulses and structured to include an optical interferometer to process the reflected probe light pulses along two different optical paths to generate different optical output signals from the reflected probe light pulses along different optical paths, and optical detectors to receive the optical output signals from the optical interferometer; and a device controller coupled to the optical detection unit to extract information on spatial distribution of acoustic—or vibration—or strain-dependent characteristics as a function of distance along the fiber link under test.

The apparatus for non-contact damping vibration of a vibrating optical fiber moving over an optical fiber path includes an air bearing and an air supply. The air bearing includes a body having an aperture defined by an inner surface and a central axis that passes through the center of the aperture and along which lies the optical fiber path. A plurality of nozzles is distributed around the inner surface and directed toward the central axis. An air conduit within the body is in pneumatic communication with the plurality of nozzles. The air supply is pneumatically connected to the air conduit and is configured to supply pressurized air to the air bearing. The pressurized air is directed through the nozzles to the vibrating optical fiber and impinges on the optical fiber to damp the vibration of the vibrating optical fiber.

A sensor includes at least one optical waveguide having a mode-field diameter greater than 11 μm and an optical reflector optically coupled to the at least one optical waveguide. The optical reflector includes a first substrate portion configured to reflect a first portion of a light beam back to the at least one optical waveguide and a diaphragm configured to reflect a second portion of the light beam back to the at least one optical waveguide. The diaphragm is responsive to a perturbation by moving relative to the first substrate portion. The light beam is centered on a region between the first substrate portion and the diaphragm.

A method of acousto-optic imaging may include receiving a first signal from a first sub-aperture of a sensor array. The first sub-aperture may comprise one or more array elements of a first type. The method may further include receiving a second signal from a second sub-aperture of the sensor array. The second sub-aperture may comprise one or more array elements of a second type different from the first type. In some variations, the first type of array element may be an acoustic transducer (e.g., piezoelectric transducer) and/or the second type of array element may be an optical sensor (e.g., optical resonator such as a whispering gallery mode (WGM) resonator). The method may further include combining the first signal and the second signal to form a synthesized aperture for the sensor array.

An acoustic sensor includes at least one optical waveguide configured to emit an optical beam, a substantially planar first substrate optically coupled to the at least one optical waveguide, and a substantially planar second substrate substantially parallel to the first substrate, affixed to the first substrate, and affixed to the at least one optical waveguide. The first substrate is configured to be illuminated by the optical beam and to reflect at least a portion of the optical beam to the at least one optical waveguide. The first substrate includes a first substrate portion configured to reflect a first portion of the optical beam back to the at least one optical waveguide and a diaphragm configured to reflect a second portion of the optical beam back to the at least one optical waveguide. The diaphragm is responsive to a perturbation by moving relative to the first substrate portion. The optical beam is centered on a region between the first substrate portion and the diaphragm.

A method for determining tree infestation includes placing an optical fiber around a trunk of a tree; recording with a distributed acoustic sensor (DAS) box a Rayleigh signal reflected from the tree, along the optical fiber; processing the Rayleigh signal to obtain a processed signal; calculating a signal-to-noise ratio (SNR) of the processed signal for the tree; and comparing the SNR to a threshold value and counting an alarm if the SNR is larger than the threshold value. The SNR is defined as a ratio between (1) a maximum value of a processed signal and (2) a minimum value of the processed signal.

An optical fiber sensing system is acquired by adding an optical fiber sensing function to an optical communication cable system, and the optical fiber sensing is performed by an interrogator by sending probe light to an optical fiber, detecting backscattered light of the probe light, and performing sensing on environmental information around the optical fiber. A first sensing device installed at a remote place different from a terminal station of the optical communication cable system includes the interrogator, a power source unit configured to receive power via the optical communication cable system and supply power into the device, and a communication unit configured to communicate with a second sensing device. The interrogator generates sensing data at each point on the optical fiber by performing sensing on environmental information around the optical fiber being connected to the first sensing device.

A sensor includes at least one optical waveguide and an optical reflector optically coupled to the at least one optical waveguide. The optical reflector includes a first substrate portion configured to reflect a first portion of a light beam back to the at least one optical waveguide and a diaphragm configured to reflect a second portion of the light beam back to the at least one optical waveguide. The diaphragm is responsive to a perturbation by moving relative to the first substrate portion. The light beam is centered on a region between the first substrate portion and the diaphragm.