A civil engineering structure monitoring system according to the present disclosure is provided with: a cable (20) including communication optical fibers and laid in a civil engineering structure (10); a reception unit (331) configured to receive, from at least one of the communication optical fibers included in the cable (20), an optical signal including a pattern corresponding to a deteriorated state of the civil engineering structure (10); and a detection unit (332) configured to detect the deteriorated state of the civil engineering structure (10) based on the pattern.

A distributed fiber sensing system and method of use. The system may comprise an interrogator configured to receive a Brillouin backscattered light from a first sensing region and a second sensing region, a first fiber optic cable optically connected to the interrogator, a proximal circulator, and a distal circulator, and a second fiber optic cable optically connected to the interrogator, the proximal circulator, and the distal circulator. The system may further comprise a downhole fiber optically connected to the first fiber optic cable and the second fiber optic cable and wherein the first sensing region and the second sensing region are disposed on the downhole fiber. The method may comprise generating and launching a light pulse from an interrogator and through a first fiber optic cable to a downhole fiber and receiving a Brillouin backscattered light from a first sensing region and a second sensing region.

A slight movement of the ground is detected. A cable, which includes an optical fiber, is provided to have friction with the ground in such a way that the optical fiber is expanded and contracted in accordance with the movement of the ground. An optical output unit outputs a monitoring light to the optical fiber. A partial reflection unit is provided on a path of the optical fiber in the cable and partially reflects the monitoring light. An optical reception unit receives a reflection light reflected by the partial reflection unit. A calculation unit measures the length of the optical fiber to the partial reflection unit based on a round-trip propagation time of the reflection light that has been received and monitors its changes over time.

A method for assembling a strain gauge arrangement for an axle counter, includes: a strain sensor element; a carrier, to which the strain sensor element is fastened; and a railroad track structure to be monitored. When the carrier is fastened to the structure at least a part of it is kept in an elastically deformed state. The carrier is embodied with a first carrier piece opposing a second carrier piece. The strain sensor element is fastened to the first carrier piece with a first fixing point, to the second carrier piece with a second fixing point, and to neither the first nor the second carrier piece with a central section between the fixing points. At least the part of the carrier is elastically braced by means of a bracing element for when adhesively bonding to the structure to be monitored. Thereafter the bracing element is removed.

A multibend sensor is able to provide information regarding bending of the sensor data in a manner able to mitigate error propagation. A reference strip and a sliding strip are separated from each other by a spacer. Electrodes are located on the reference strip and the sliding strip. The bending of the multibend sensor will be reflected in the shifting of the sliding strip with respect to the reference strip and the measurements obtained from the electrodes. A finger may be operably connected to the reference strip, wherein the finger extends in the direction of the sliding strip, wherein movement of the reference strip with respect to the sliding strip is translated through the finger.

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.

A generator slot wedge is described. The slot wedge includes a surface and further includes a strain gage. The strain gage is attached to the surface of the slot wedge. A method of determining the strain on the generator slot wedge of the generator via the strain gage is also described.

Provided is a device for measuring at least one dimension of an object. The device includes at least one body configured to be arranged along, or around, the object. The, or each, body carries an elongate stretchable waveguide and is configured to allow stretching the waveguide along its length when arranged along, or around, the object. The, or each, waveguide is associated with a sensor. The, or each, sensor includes a light emitter arranged and operable to emit at least one light pulse through the associated waveguide, and a light detector arranged to receive the at least one light pulse conveyed through the waveguide. The device also includes a communication module communicatively coupled with the, or each, sensor, and configured to communicate measurement data from the, or each, sensor to a processor to allow determining the at least one dimension. Systems and methods for measuring at least one dimension of an object are also disclosed.

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 relates to an optical fiber sensor, comprising an optical fiber having embedded therein at least one fiber core (14, 16, 18, 20) extending along a length of the optical fiber, the at least one fiber core having a plurality of single fiber Bragg gratings (40, 42, 44) arranged in series along the at least one fiber core (14, 16, 18, 20), wherein each fiber Bragg grating (40, 42, 44) has a single reflection spectrum around a single reflection peak wavelength when interrogated with light in an untrained state of the at least one fiber core (14, 16, 18, 20), wherein the reflection peak wavelengths of the single reflection spectra are different from fiber Bragg grating (40, 42, 44) to fiber Bragg grating (40, 42, 44) along the at least one fiber core. Also described is an optical system and a method of interrogating an optical fiber sensor.