An optical fiber characteristics measuring apparatus includes: a light source that outputs frequency-modulated continuous wave of light; a first optical branching unit that branches the continuous light into pump light and reference light; a second optical branching unit that outputs backscattered light generated by making the pump light incident from one end of an optical fiber to be measured, wherein the backscatterd light is Brillouin scattering in the optical fiber; a detector that detects interference light of the backscattered light and the reference light; a measuring unit that measures characteristics of the optical fiber by using a detection signal output from the detector; and a controller that controls the light source to change modulation frequency of the continuous light in units of one period or half a period of a modulation period corresponding to the modulation frequency.

Device for measuring the endogenous deformations of a structure of materials, during the transition of said structure from a liquid phase to a solid phase, comprising: a uniaxial test body suitable for being embedded in the structure; a deformation measurement fiber attached to the interior of the test body; a system connected to the measurement fiber and suitable for detecting signals representative of the deformations of the measurement fiber and for determining the endogenous deformations from these signals and from known mechanical properties of the materials of the test body,

the test body having a rigidity comprised between 2 and 5 gigapascals.

Various embodiments may provide a strain-sensing apparatus configured to be attached to a micrometeoroid and orbital debris (MMOD) shielding layer and data collection equipment in communication with the strain-sensing apparatus configured to detect an occurrence, a time, a location, and/or a severity of a MMOD strike on the MMOD shielding layer. The various embodiments may enable detection and/or location of potentially harmful MMOD strikes on both human occupied and unmanned spacecraft.

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.

A fibre-optic measurement system equipped with a controlled light generation system (1) and a receiving system (2) connected via an optical path which comprises a directional device (4) and which, in addition, has a processing unit (9) for controlling the light generation system (1) and for receiving and processing the signal from the receiving system (2), according to the invention, it is characterized by the fact that it has a selective mode device (5) and is adapted to be connected to a fibre-optic telecommunications network by a selective mode device (5) and the processing unit (9) is adapted to implement the OFDR and/or COTDR measurement technique for measuring changes in the optical distance and processing them into one or more parameters. Moreover, the object of the invention is also the method of adaptation of a telecommunications network into a sensor network and a fibre-optic measurement and communication system.

In some embodiments, a distributed nondestructive inspection method for slickline cable structural defect detection transmits a light pulse along an optical waveguide in the slickline cable. A reflected light signal is 5 received from the optical waveguide in response to the light pulse. Defects can then be determined in the slickline cable based on variations in scattering intensity, phase shift, specific spectral signature, power spectral density, strain amplitude, and/or transmission loss of the reflected light signal as compared to the light pulse.

An apparatus for measuring a length of an optical resonant cavity includes a frequency tunable light source, a beam splitter, a frequency modulator and an optical resonant cavity. The frequency tunable light source emits a beam. The beam splitter is disposed on the optical path of the beam for dividing the beam into a first beam and a second beam. The frequency of the second beam is modulated by the frequency modulator to differ from the frequency of the first beam by a beat frequency. The optical resonant cavity is disposed on the main optical path of the first beam and the main optical path of the modulated second beam. The first beam and the modulated second beam enter the optical resonant cavity for measuring a length of the optical resonant cavity, and a variation in cavity length is calculated from the beat frequency.

A system and method are provided for distributed acoustic sensing in a multicore optical fiber. The system includes a transmitter for simultaneously propagating a sequence of M light pulses through the multicore 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 multicore 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 multicore optical fiber and detecting an environmental perturbation in the multicore optical fiber based on an evaluation of a propagation of the sequence of M light pulses through the multicore optical fiber.

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.

Disclosed embodiments include a distributed nondestructive inspection method and system for slickline cable structural defect and mechanical strength degradation inspection. One method may include transmitting a light pulse along an optical fiber embedded in a slickline cable. A reflected light signal is received from the optical fiber in response to the local strain induced refractive index variation. Defects and mechanical strength degradation may be determined by time-dependent time-domain and frequency-domain data analyses of the dynamic strain signals and power spectral density variation as a function of time and cable location.