An optical inspection system includes an optical fiber sensor, an optical filter, a signal processor, and a corrector. The optical fiber sensor outputs a first optical signal having a temporal change in a wavelength corresponding to a temporal change in an amplitude of a vibration propagating in an inspection target object or a temporal change in a displacement of the inspection target object. The optical filter converts the first optical signal into a second optical signal having a temporal change in an intensity. The signal processor acquires inspection information on the inspection target object on the basis of the second optical signal. The corrector corrects a correspondence relationship between the temporal change in the wavelength and the temporal change in the intensity by changing a wavelength characteristic of the optical filter. The correspondence relationship is directed to converting the first optical signal into the second optical signal.

The optical fiber sensing method of the present invention includes steps of: joining heat shrinkable tubes to two ends of a sensing segment of an optical fiber; coupling a fixing element on the heat shrinkable tube below the sensing segment; detachably connecting at least one floating element to the fixing element; placing the floating element into a fluid; and providing an input signal to the sensing segment and generating an output signal after the input signal is processed by the sensing segment, wherein the tensile force applied to the sensing segment would change with variation of the buoyant force upon the floating element, resulting in change of the output signal. Accordingly, the optical fiber sensing method has numerous advantages, including rapid on-site construction, recyclability of components and changeability of design parameters.

An apparatus for locating a measurand anomaly, such as a hot-spot, along an optical waveguide is provided having: an optical waveguide, a light source configured to transmit light along the waveguide and a plurality of sensors provided along the waveguide. Each sensor is configured to reflect a portion of light propagating along the waveguide at a respective sensor wavelength corresponding to a measurand. The plurality of sensors is configured into one or more sets according to their sensor wavelengths, each set comprising a plurality of sensors with respective sensor wavelengths, wherein the sensors are configured such that the sensor wavelength for each sensor in a respective set is substantially equal when the measurand experienced by each of the sensors in that set is equal. The apparatus further includes a detector configured to monitor the light reflected by the sensors, and a control system.

A device for testing overall anchorage performance of a basalt fiber reinforced plastic (BFRP) anchor cable includes an anchor cable anchoring system and a data acquisition system. The anchor cable anchoring system includes a test bed, BFRP arranged over the test bed, and a distributed optical fiber bonded to a surface of the BFRP, the test bed being provided with an anchoring section at one end and an outer anchoring section at the other end, the anchoring section anchors one end of the BFRP, and the outer anchoring section anchors the other end of the BFRP. The data acquisition system includes a modem and a grating connected to two ends of the distributed optical fiber in series, and a center hole jack and a dynamometer arranged between the outer anchoring section and an end of the test bed, and the BFRP penetrates the center hole jack and the dynamometer.

A system and method are provided for distributed acoustic sensing in a multimode optical fiber. The system includes a transmitter for simultaneously propagating a sequence of M light pulses through the multimode optical fiber using a spatial mode selected from a set of N spatial modes provided by a spatial mode selector for the transmitter that is coupled to an input to the multimode optical fiber, with M and N being respective integers greater than one. The system further includes a receiver for receiving the sequence of M light pulses at an output of the multimode optical fiber and detecting an environmental perturbation in the multimode optical fiber based on an evaluation of a propagation of the sequence of M light pulses through the multimode optical fiber.

A measuring system and method that computes and analyzes sensor data fused with multiple mechanical and thermally induced strain measurements is provided. Further, the measuring system and method realizes physics-based relations between sensor readings due to mechanical and thermal sources by optimally de-coupling a total strain into its mechanical and thermal components. The measuring system and method also auto-tunes coefficients involved in the optimal de-coupling equations using sensor specification data and previous system test results for initialization.

A method for monitoring the structural health of a structure that supports guided propagation modes of elastic waves, includes the following steps: a) acquiring an ambient noise propagating through the structure by means of at least one pair of non-collocated elastic-wave sensors; b) estimating a function representative of an impulse response of the structure for elastic propagation between the constituent sensors of said pair; c) extracting at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of this function representative of an impulse response; and d) estimating at least one parameter indicative of a mechanical property of a constituent material of the structure from the dispersion curve obtained in step c). A system for implementing such a method is also provided.

A deformation sensing apparatus comprises a propagation channel, a transmitter coupled to a first end of the propagation channel, a receiver coupled to a second end of the propagation channel, and a controller. The propagation channel is deformable and the controller instructs the transmitter to transmit a signal, instructs the receiver to capture one or more measurements of the transmitted signal, and determines a bend in the propagation channel based on the one or more measurements. In one embodiment, the transmitter is a light source, the propagation channel is an optical fiber, and the receiver is a photodiode. The propagation channel is made of a material that has a variation in a refractive index responsive to applied mechanical stress. The deformation sensing apparatus may also include a polarizer positioned between the transmitter and the propagation channel and a wave plate positioned between the propagation channel and the receiver.

A diagnosis apparatus includes a fiber optic sensor, a collection processor, and a self-diagnosis processor. The fiber optic sensor is configured to be disposed over a target. The collection processor is configured to perform a collection process that collects measurement data related to the target obtained by the fiber optic sensor. The self-diagnosis processor is configured to perform a self-diagnosis process before the collection processor starts the collection process. The self-diagnosis process obtains an output value related to calibration of the fiber optic sensor, causes the collection processor to start the collection process when the output value falls within a proper range, and outputs an error when the output value falls outside the proper range.

A fiber-optic sensor system includes a structure having a fiber-optic cable operatively connected thereto. The system includes a network controller with an interrogator operatively connected to the fiber-optic cable to receive optical energy indicative of a characteristic of the structure therefrom and convert optical energy to electrical energy and electrical energy to optical energy for data communication. A sensor and/or a data source are operatively connected to the fiber-optic cable through the network controller to transmit data through the fiber-optic cable and receive data therefrom.