A monitoring system according to the present disclosure includes an optical fiber (10) laid on a ground or a seabed, an optical fiber sensing unit (21) configured to receive an optical signal from the optical fiber (10) and detect a vibration produced in the ground or the seabed based on the optical signal, and an analyzing unit (22) configured to identify a natural phenomenon that has caused the detected vibration based on a unique pattern of the detected vibration.

According to one example embodiment, an optical fiber sensor includes an optical fiber cable and a device body configured to cause an optical pulse signal to be incident on the optical fiber cable and identify, from intensity change of backscattered light of the incident optical pulse signal and an arrival time of the backscattered light, a prescribed environmental change having occurred in a vicinity of the optical fiber cable and an occurrence location of the environmental change, in which the device body performs correction of a sensing location on the optical fiber cable, based on environmental change information including the identified occurrence location and installation location information of the optical fiber cable.

In some implementations, a device may obtain responsivity data for segments of a fiber optic cable. The device may receive, from a sensor device, vibration data associated with the fiber optic cable, the vibration data being produced by a vibration source in or on soil associated with the fiber optic cable. The device may normalize, based on the responsivity data, the vibration data. The device may determine, based on the normalized vibration data, a distance of the vibration source from the fiber optic cable. The device may perform one or more actions based on the distance satisfying a distance threshold.

It is intended to provide a phase measurement method and a signal processing device that are capable of reducing influence of noise of a measuring device without increasing the peak intensity of an incident light pulse when measuring the phase of scattered light in DAS-P.

A phase measurement method according to the present invention causes wavelength-multiplexed pulse light to be incident on a measurement target optical fiber, produces a scattered light vector obtained by plotting scattered light from the measurement target optical fiber for each wavelength onto a two-dimensional plane having the in-phase component thereof on the horizontal axis and the orthogonal component thereof on the vertical axis, rotates the produced scattered light vector for each wavelength at each place in the measurement target optical fiber to align the directions of the vectors, generates a new vector by calculating the arithmetic average of the vectors having the aligned directions, and calculates the phase by using the values of the in-phase and orthogonal components of the generated new vector.

A method and system for determining deformation in a cable, where a sensing optical fiber arrangement is applied along the cable. The method includes injecting a forward pulse pump signal in the optical fiber in a forward direction of the optical fiber and injecting a reverse probe signal in the optical fiber in a reverse direction of the optical fiber. A stimulated Brillouin backscattering is measured and, based on the Brillouin backscattering measurement, information is provided about a deformation of the cable. The forward pulse pump signal is provided as a sum of a stationary signal component and an interrogation pulse component, the stationary signal component has an energy below a Brillouin activation level and the interrogation pulse signal component has an energy which results in that the sum of the stationary signal component and the interrogation pulse signal component exceeds the Brillouin activation level.

A spatial averaging method for a coherent distributed acoustic sensing (DAS) system that employs differential beating and polarization combining of signals for two locations along a length of optical sensing fiber to determine phase change in-between every location along the length of the optical sensing fiber and a moving average using polarization combining output to reduce any Rayleigh fading before phase determination.

Distributed fiber optic sensing (DFOS)/distributed acoustic sensing (DAS) techniques coupled with frequency domain decomposition (FDD) are employed to determine the presence of 120 HZ operating power frequency to determine when street lights are energized and on thereby providing continuous status monitoring of the operational status of street lights and locating affected street lights at a particular utility pole location.

One embodiment described herein provides a system for distributed fiber sensing. The system can include a plurality of network elements (NEs) in an optical transport network (OTN) and a control-and-management module coupled to the NEs. A respective network element (NE) can include a first wavelength coupler configured to separate an optical supervisory channel (OSC) signal from a data-carrying signal received from a fiber span, a polarization-measurement unit configured to perform a polarization measurement on the OSC signal, and a transmitter configured to transmit an outcome of the polarization measurement to the control-and-management module, thereby facilitating distributed fiber sensing based on the outcome of the polarization measurement.

An optical fiber sensing system according to the present disclosure includes a sensing optical fiber (20), a medium (10) with which the sensing optical fiber (20) is integrated, and which is arranged in a monitoring target (50), an optical fiber detection unit (30) which is connected to the sensing optical fiber (20) integrated with the medium (10), the optical fiber detection unit (30) is configured to receive an optical signal from the sensing optical fiber (20), and detect a pattern according to a state of the monitoring target (50), contained in the optical signal, and a state detection unit (40) configured to detect a state of the monitoring target (50), based on the pattern contained in the optical signal.

Disclosed is a method for reconstructing an electromagnetic vector wave backscattered in all or part of an optical fiber. According to an embodiment of the method a light signal of a frequency v.sub.0 or v.sub.0+v.sub.A is injected into the optical fiber. A step of polarization-resolved heterodyne optical detection includes the generation of at least two orthogonally polarized backscattered light signals, producing a beat preferably of a frequency v.sub.A. At least one photodetector converts the orthogonally polarized backscattered light signals into initial analog signals. Electrical homodyne detection is performed by an IQ demodulator so as to generate I and Q demodulated analog signals. A processing module reconstructs the electromagnetic vector wave backscattered in all or part of the optical fiber.