An optical fiber characteristic measurement apparatus (1) includes: a light source (11) configured to output a laser beam of which frequency is modulated; an incident part (12, 13, 14, and 15) configured to make the laser beam output from the light source be incident from one end and another end of an optical fiber (FUT) as continuous light (L1) and pulsed light (L2), respectively; a light detector (16) configured to detect light projected from the optical fiber and output a detection signal (D1); and a detector (17 and 18a) configured to detect, in a first period (T1) in which scattering light based on the continuous light and the pulsed light is projected from the optical fiber and a second period (T2) shorter than the first period, in which the scattering light is not projected from the optical fiber, the scattering light based on integrated values acquired by integrating the detection signal for a predetermined time.

In a measurement requiring a high space resolution using S-BOTDR, a pulse train composed of a plurality of pulses having the interval between the pulses longer than the phonon lifetime is interpulse-code-modulated. A Golay code is used for the interpulse code modulation to eliminate the sidelobes of the correlation in using a technique of correlation. In a technique without using correlation, an Hadamard matrix is used for the interpulse code modulation and the resultant matrix is inverted in the signal processing.

A method and system for determining deformation in a cable 110, wherein a sensing optical fiber arrangement is applied along the cable 110. The method comprises injecting a forward pulse pump signal in the optical fiber in a forward direction of the optical fiber; injecting a reverse probe signal in the optical fiber in a reverse direction of the optical fiber; measuring a stimulated Brillouin backscattering; and based on the Brillouin backscattering measurement, providing information 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, and advantageously, 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. The method and system may be used during deployment of a subsea power cable 110 to a sea bottom 100 from a cable reel 130 positioned on the deck of a cable-laying vessel 120 floating on a sea surface 140.

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, the beat signal 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.

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.

A method of providing in-line Raman amplification in an optical fiber sensing system, including the procedures of generating a probe light having a probe wavelength, transmitting the probe light into an optical fiber, generating at least one Raman pump light at a respective pump wavelength, the pump wavelength being shorter than the probe wavelength, generating at least one Raman seed light at a respective seed wavelength, the seed wavelength being between the pump and probe wavelengths, transmitting the Raman pump light into the optical fiber, transmitting the Raman seed light into the optical fiber and propagating the Raman pump light, the Raman seed light and the probe light along the optical fiber to achieve distributed Raman amplification of signal light produced by the probe light as it propagates along the optical fiber.

Systems, methods, and apparatuses for detecting components of a multiphasic flow are disclosed. A flowmeter may include a plurality of optical fibers disposed across a fluid flow. The optical fibers may generate backscattering of a portion of a laser beam transmitted along the optical fibers. The backscattering may be produced by a grating formed by zinc dicyanoaurate formed in each of the optical fibers. Heterodyne detection may be used to determine a Brillouin frequency shift that is used to determine strain and temperature measurements at different locations along the optical fibers. Artificial Intelligence uses the strain and temperature measurements to determine a flow regime of the fluid flow and flow rates of components forming the fluid flow.

Aspects of the present disclosure describe systems, methods and structures providing detection and localization of disaster-related indoor events via hybrid ethernet/optical fiber cable.

A distributed optical fibre sensor is discussed which is arranged to detect acoustic vibration and at least a first of two or more other measurands, which could be for example two or more of changes in temperature, changes in static pressure, and changes in static strain. At least first and second optical waveguides are arranged to have optical path length response characteristics to at least one of the other measurands which are different from each other, and an analyser is arranged to determine at least said first other measurand using differences between the interference signals from each of the optical waveguides.

The present invention discloses a computational distributed fiber-optic sensing method and system. The method includes: determining a signal source for modulating intensity of incident light, where the signal source is a binary sequence; using an optical pulse sequence obtained after modulation is performed using the signal source, as an incident light signal, and emitting the incident light signal to an optical fiber; acquiring, according to specified sampling frequency, a scattered light signal obtained through optical fiber scattering; determining, according to the incident light signal and the scattered light signal, a time-domain reconstructed image of a to-be-detected light signal by using a time domain-based differential ghost imaging protocol; and determining a sensing signal of the optical fiber according to the time-domain reconstructed image of the to-be-detected light signal. The computational distributed fiber-optic sensing method and system provided in the present invention feature low sampling frequency, low device complexity, and low costs.