An improved technique for acoustic sensing involves, in one embodiment, launching into a medium, a plurality of groups of pulse-modulated electromagnetic-waves. The frequency of electromagnetic waves in a pulse within a group differs from the frequency of the electromagnetic waves in another pulse within the group. The energy scattered by the medium is detected and, in one embodiment, may be used to determine a characteristic of the environment of the medium. For example, if the medium is a buried optical fiber into which light pulses have been launched in accordance with the invention, the presence of acoustic waves within the region of the buried fiber can be detected.

A road monitoring system according to the present disclosure includes: a cable (20) including a communication optical fiber, being laid on a road (10); a reception unit (331) configured to receive an optical signal from at least one communication optical fiber included in the cable (20); and a detection unit (332) configured to detect a pattern according to a state of the road (10), based on the optical signal, and detect an abnormal state of the road (10), based on the detected pattern according to the state of the road (10).

An advance in the art is made according to aspects of the present disclosure directed to the detection and localization of a substantially static weight situated on aerial telecommunications fiber optic cable through the effect of phase-distributed acoustic sensing (ϕ-DAS) and signal analysis of ambient data. In sharp contrast to the prior art, our inventive method does not require a special optical fiber arrangement or type of fiber nor is it susceptible to range limitations that plague the prior art.

A fully distributed magnetic adsorption multi-parameter sensing cable, which is configured to be installed on the wall of a metal pipeline, includes an outer sheath, a sensing component arranged in the outer sheath, and a fully distributed magnetic adsorption reinforcement (FDMAR) arranged in the outer sheath and on a peripheral side of the sensing component. The outer sheath is attached to the wall of the metal pipeline by the FDMAR. A magnetic adsorption force between the FDMAR and the wall of the metal pipeline is able to be adjusted by changing the size of the FDMAR and the distance between the FDMAR reinforcement and the wall of the metal pipeline. The fully distributed magnetic adsorption multi-parameter sensing cable has the advantages of good adsorption effect and high sensitivity.

Interferometric measurement signals are detected by a single optical interferometric interrogator for a length of a sensing light guide and an interferometric measurement data set corresponding to the interferometric measurement signals is generated. The interferometric measurement data set is transformed into a spectral domain to produce a transformed interferometric measurement data set. The transformed interferometric measurement data set is compared to a baseline interferometric data set to identify a time-varying signal corresponding to a time-varying disturbance. The baseline interferometric data set is representative of the sensing light guide not being subjected to the time-varying disturbance. A compensating signal is determined from the time-varying signal and used to compensate at least a portion of the interferometric measurement data set for the time-varying disturbance as part of producing a measurement of the parameter.

A triggering device includes an optical fiber (126) configured for optical shape sensing. A supporting element (104) is configured to support a portion of the optical fiber. An interface element (106) is configured to interact with the optical fiber associated with the supporting element to cause a change in a property of the fiber. A sensing module (115) is configured to interpret an optical signal to determine changes in the property of the fiber and accordingly generate a corresponding trigger signal.

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 computer-implemented event statistic generation for intrusion detection comprises processing a plurality of return signals from a coherent optical time-domain reflectometer into time-domain signals for each of a plurality of sensor bins, the plurality of return signals corresponding to a plurality of stimulation pulses injected into an optical sensor fiber during a time period. For each sensor bin, transforming the respective time-domain signal into a corresponding frequency-domain signal, calculating, from the respective frequency-domain signal, a first signal power area of a first frequency band expected to contain system noise and a second signal power area of a second frequency band expected to contain any energy related to at least a first event; and generating an event statistic proportional to the ratio of the second signal power area to the first signal power area at least in part by dividing the second signal power area by the first signal power area.

Aspects of the present disclosure describe systems, methods and structures for coherent distributed sensing that employs a moving average method among locations along a sensing fiber employing a user configured number of taps that involves location grouping and a group's internal phase alignment followed by an inter-group phase alignment and combining. Our method employs two steps of rotation to achieve the alignment: intra-group rotation and inter-group rotation to align the phase of all participating sensing fiber locations.

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.