The invention includes an apparatus (110) and method (152) for determining a deformation (170) of a three-dimensional, flexible structure in the form of a tubular construct (112) with a minimum of optical waveguides. An optical waveguide (116) is introduced into the tubular construct (112), where the optical waveguide (116) extends as a helical winding (118) within the tubular construct (116) and has a multiplicity of strain measuring means (126). The configuration of the apparatus and method performed reduces the average material load of the strain measuring means and improves resolution and measurement range of the sensor (optical waveguide) while maintaining readout frequency of the strain measurements. The apparatus (110) also includes an evaluation device (130) configured to determine the deformation of the tubular construct (112), in particular in relation to an axis, surface and/or volume of the tubular construct (112), from measurement values (154) from the multiplicity of strain measuring means (126).

A method for detecting and determining a location of an overheat condition includes producing a narrowband optical signal with a laser source and optical pulse generator. The optical signal is sent into the optical fiber. A plurality of reflected optical signals is received. Reflection intensities are detected using a photodetector. The reflection intensities are compared with a triggering threshold. Response times of the reflected optical signals are recorded whenever the reflection intensity of the optical signals is greater than the triggering threshold. The narrowband optical signal is adjusted to another wavelength. An anomaly reflected optical signal is identified using a characteristic of the timings obtained through a range of wavelengths. The location of the overheat condition recorded response times is calculated. The location and existence of the overheat condition is communicated.

A system may include a first sensor of a first type and a second sensor of a second different type and having a detector. A field of view of the second sensor may be formed by a plurality of regions of interest (ROIs) defined by the detector. Control circuitry of the system may be configured to perform operations including obtaining, from the first sensor, first sensor data representing an environment, and determining, based on the first sensor data, information associated with a feature of interest within the environment. The operations may also include determining, based on the information, a particular ROI that corresponds to an expected position of the feature at a later time, obtaining a plurality of ROI sensor data from the particular ROI instead of obtaining full-resolution sensor data, and analyzing the plurality of ROI sensor data to determine one or more attributes of the feature.

A distributed fiber-optic acoustic sensing system and a signal processing method. The distributed fiber-optic acoustic sensing system is based on a high spatial resolution distributed fiber-optic acoustic sensor. The interval between adjacent sensing units is centimeter or millimeter level. Through specific digital signal processing, signal enhancement can be realized, noise in the system and environment are suppressed, at the same time, problems such as interference fading is solved, and the sensor signal-to-noise ratio of subunits can be increased by two to three orders of magnitude. Each subunit can serve as an independent high-sensitivity sensor for sensing. The multiple subunits can form one or more new sensor arrays. The azimuth estimation and spatial orientation of signal sources can be realized by the array signal processing method.

The present invention discloses a real-time normalization apparatus and method of the PGC demodulation in a sinusoidal phase modulation interferometer. An optical setup containing a measuring interferometer and a monitoring interferometer is constructed. An electro-optic phase modulator is placed in the common reference arm of the two interferometers. High-frequency sinusoidal wave modulation and low-frequency triangular wave modulation are applied to the electro-optic phase modulator at the same time. Sinusoidal modulation is used for generating phase carrier, and PGC demodulation is performed to obtain quadrature signals containing the phase information to be measured. Triangular wave modulation makes the quadrature signals change periodically. Ellipse fitting is performed on the Lissajous figure corresponding to the quadrature signals, and real-time normalization of the PGC demodulated quadrature signals is achieved. By calculating the variation of the phase difference between the two interference signals, the measured displacement is obtained, and nanometer scale displacement measurement is achieved.

An optical sensor system with two or more optical sensors; two or more receivers; and an optical de-multiplexing system. Each optical sensor includes a fibre grating with a different wavelength characteristic. Each receiver includes a slope filter and a light detector and is associated with a respective one of the optical sensors. The optical de-multiplexing system is arranged to route light from each of the optical sensors to its associated receiver based on a wavelength of the light.

A method for determining a length of a span of electrically conductive material, comprising a first voltage measurement across the entire span, and a second voltage measurement across a constant-length segment of the span. The dual measurements allow the calculation of the span length in a manner that is robust to many disturbances including ambient temperature, material temperature, and material stress and fatigue.

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.

An improved optical fiber distributed acoustic sensor system uses an optical fiber having reflector portions distributed along its length in at least a first portion. The reflector portions are positioned along the fiber separated by a distance that is equivalent to twice the distance an optical pulse travels along the fiber in a single sampling period of the data acquisition opto-electronics within the sensor system. No oversampling of the reflections of the optical pulses from the reflector portions is undertaken. The sampling points for data acquisition in the sensor system are aligned with the reflections that arrive at the sensor system from along the sensing fiber. Adaptive delay componentry adaptively aligns the reflected optical signals (or their electrical analogues) with the sampling points. Control over the sampling points can re-synchronise the sampling points with the returning reflections. Reflection equalisation componentry may reduce the dynamic range of the returning reflections.

A photoelectric sensor includes a connecting section for light projection to which a light propagation member for light projection optically coupled to a light emitting element is connected, a connecting section for light reception to which a light propagation member for light reception optically coupled to the light receiving element is connected, a signal generating unit configured to compare a light reception signal generated by the light receiving element and a threshold and generate a detection signal indicating a result of the comparison, a first light emitting element for indication optically coupled to the connecting section for light reception, and a mounting substrate on which each of the first light emitting element for indication and the light receiving element is positioned in the connecting section for light reception or one of the first light emitting element for indication and the light receiving element is positioned via the other.