It is an object to enable offline measurement with a high SN ratio of the phase of scattered light of an optical fiber to be measured in an optical receiving system for real-time measurement (direct measurement). The phase measurement method according to the present invention performs coherent detection of scattered light using a 90-degree optical hybrid, obtains an estimated quadrature component value by averaging a measured quadrature component value that is directly measured and a calculated quadrature component value obtained by Hilbert transforming a measured in-phase component value that is directly measured, obtains an estimated in-phase component value by averaging the measured in-phase component value and a calculated in-phase component value obtained by inverse Hilbert transforming the measured quadrature component value, and calculates the phase of scattered light based on the estimated quadrature component value and the estimated in-phase component value.

The present invention provides a method for measuring an optical sensor system comprising an array of intrinsic fiber optic sensors at an interrogator comprising an optical source and an optical detector. The method comprises the steps of emitting an optical signal to an array of intrinsic fiber optic sensors; detecting optical responses to the emitted signal from the sensors; associating each detected optical response with an individual sensor by determining within which region among a plurality of detection regions assigned to the individual sensors the optical response is detected wherein each detection region corresponds to a wavelength range in the bandwidth of the optical sensor system; and performing signal processing on each optical response to measure the value of the physical parameter detected by its associated sensor. A calibration of the detection region assigned to each sensor is performed at predetermined intervals.

A self-heterodyne phase-sensitive optical time domain reflectometry (φ-OTDR) system with a free multi-spatial resolution includes a narrow linewidth laser source, a 1×3 fiber-optic coupler, three acousto-optic modulators (AOMs), a 3×1 fiber-optic coupler, two time-delay fibers, an erbium-doped fiber amplifier (EDFA), a circulator, a photodetector, an electrical amplifier, three filters, a data acquisition card, a pulse signal generator, and a driver module. A plurality of acousto-optic modulators using the same driver are used to couple probe light with different pulse intervals and different frequency shifts and then inject the probe light into a fiber, such that a self-heterodyne detection structure with a multi-spatial resolution is implemented, which suppressed optical background noise such as coherent fading noise, phase noise introduced by a frequency drift of a light source, and pseudo-random noise (PRN).

A utility pole location specifying system according to the present disclosure includes a cable (20) containing a communication optical fiber disposed in a utility pole (10), a receiving unit (331) configured to receive an optical signal containing a characteristic pattern of the utility pole (10) from at least one communication optical fiber contained in the cable (20), and a specifying unit (332) configured to specify a location of the utility pole (10) based on the characteristic pattern.

To facilitate the acquisition of environment information for a distant observation point, this environment information acquisition system is made to comprise a Fiber Bragg Grating (FBG) sensor that is placed on an optical path comprising optical fiber and has a grating pitch that changes according to surrounding environment information, a detection unit for detecting the phase variation of probe light that is transmitted via the optical fiber and reflected by the FBG sensor as return light, and an environment information calculation unit for calculating surrounding environment information for the FBG sensor from the phase variation.

A directional drilling-exploring-monitoring integrated method for guaranteeing safety of an underwater shield tunnel includes: drilling a small-diameter borehole below a water area, and establishing an initial geological model; reaming the small-diameter borehole into a large-diameter borehole, placing a parallel electrical method (PEM) power cable and a monitoring optical fiber cable into the large-diameter borehole, acquiring zero field data, primary field data and secondary field data through carbon rod measurement electrodes before tunnel excavation, and processing the data with an existing inversion method to form an inversion image, thereby obtaining a refined geological model of a stratum; starting the tunnel excavation, and respectively acquiring a disturbance condition of rock and soil and a sedimentation and deformation condition of rock and soil around the tunnel during the excavation, thereby implementing safety excavation of the tunnel; and continuously monitoring the tunnel and the surrounding rock and soil in later use of the tunnel.

A distributed optical detection system comprising: a broadband optical source; and a phase and amplitude receiver for measuring phases and amplitudes of distributed backscattered signals from a sensing medium. Methods of quantitatively sensing optical path length changes along a sensing medium in a distributed manner are also disclosed.

A distributed fiber optic sensing (DFOS)/distributed acoustic sensing (DAS) system and method employing a fiber optic sensor cable that collects vibrational data of individual utility poles suspending the fiber optic sensor cable and stores the vibrational data in a central office (CO). Machine learning (ML) models are developed, trained, and utilized to analyze vibrational features of the utility poles and determine their integrity. Additionally, DFOS/DAS systems and methods according to the present disclosure determine the location(s) of fiber coils that exist along a length of a fiber optic sensor cable.

The disclosure concerns a device (101) for distributed sensing comprising: a pump generator (1) for generating an optical pump signal, a pump splitter (2) configured to split the pump signal in a number N of channels (3), each channel comprising an optical fiber (31) or a connector (32) arranged for connecting an optical fiber, a controller configured to control the pump splitter, an optical receiver (4) for receiving a backscattered signal from the optical fiber or from the connector of each channel. The pump splitter comprises a gating system comprising a gate (21) for each channel among the N channels. Each gate is associated to a given channel and has an open state allowing the pump signal to go from the pump generator to the optical fiber or the connector of the associated channel, and a closed state for which the pump signal cannot go from the pump generator to the optical fiber or the connector of the associated channel.

The present invention provides novel apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre. The present invention can be used for point sensors as well as distributed sensors or the combination of both. In particular this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. The present invention offers unique advantages in a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.