The present disclosure aims to enable measurement of a long distance exceeding 1 km with a spatial resolution of 100 μm or lower, and diagnosis of health of an optical device installed at a long distance.

An apparatus according to the present disclosure is an optical frequency domain reflectivity measuring apparatus that includes: a local light delay fiber that delays local light; an optical 90-degree hybrid that receives an input of the local light delayed by the local light delay fiber and backscattered light from the measurement target, causes the local light and the backscattered light to interfere with each other, and generates an in-phase component and an orthogonal component of a beat signal generated by the interference; and a balance photodetector that detects the in-phase component and the orthogonal component of the beat signal. In the apparatus, an optical frequency response of the measurement target is measured with respect to a relative distance based on the local light delay fiber.

Computer vision based, wide-area snow/water level estimation methods using disparity maps. In one embodiment our method provides rich depth-information using a stereo camera and image processing. Scene images at normal and snow/rain weather conditions are obtained by a double-lens stereo camera and a disparity map is generated from the scene images at left and right lenses using a self-supervised deep convolutional network. In another embodiment, our method uses a single point snow/water level sensor, a stationary monocular camera to measure snow/water levels covering a wide area.

A distributed fiber optic sensing (DFOS) system including a smart-mat that: 1) identifies indoor locations of moving persons/objects; 2) provides a 2D visual mapping; and 3) covers any blind spots with supplemental technologies including LiDAR, RF radar, etc. The DFOS system with smart-mat may be deployed virtually anywhere indoors and may even be constructed to replace carpeting. When our inventive DFOS system and smart-mat is deployed throughout an entire building, building safety and security is greatly improved by providing up-to-date localization information of building occupants while eliminating blind zones and reducing maintenance costs.

A radio-controlled, two-way acoustic modem for operating with a distributed fiber optic sensing (DFOS) system including circuitry that receives radio signals including configuration information, configures the modem to operate according to the configuration information, and generate acoustic signals that are detected by the DFOS system. The acoustic modem includes one or more sensors that detect environmental information that is encoded in the acoustic signals for further reception by the DFOS system. The received configuration information may change the operating times, sensors or other operating aspects of the modem as desired an such information may be transmitted from a fixed location or a mobile vehicle.

A method for measuring a response from an optical fiber providing distributed back reflections using a system comprising an optical source comprising a laser, an optical receiver and a processing unit is disclosed. The method comprises generating an interrogation signal and an optical local oscillator using the optical source, the interrogation signal being represented by an interrogation phasor and the optical local oscillator being represented by a local oscillator phasor; transmitting the interrogation signal into the optical fiber; and mixing the optical local oscillator with reflected light from the optical fiber and detecting a mixing product with the optical receiver to achieve a receiver output signal. The method further comprises performing a measurement that characterizes fluctuations in the local oscillator phasor; processing the receiver output signal based on the measurement result to provide a corrected receiver output signal such that an effect of fluctuations in the local oscillator phasor on the corrected receiver output signal is reduced; and applying distributed back-reflection processing on the corrected receiver output signal. Finally, the method comprises extracting the response from the optical fiber from the distributed back-reflection processing output. A system for measuring a response from an optical fiber providing distributed back reflections is also disclosed.

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.

A distributed sensing apparatus based on Optical Time Domain Reflectometry, OTDR, including an optical source; an optical splitter in optical communication with the optical source, the optical splitter having first and second outputs; a sensing fibre in optical communication with the first output of the optical splitter; a combining unit arranged to combine a reference signal derived from the second output of the optical splitter with a backscattered signal derived from the sensing fibre, wherein the combining unit comprises one or more 3×3 fused fibre couplers; and a signal processing unit configured for processing information derived from the combining unit so as to provide distributed sensing data. The combining unit includes a polarization diversity arrangement including one or more polarization sensitive elements.

According to examples, a Brillouin and Rayleigh distributed sensor may include a first laser source to emit a first laser beam, and a second laser source to emit a second laser beam. A photodiode may acquire a beat frequency between the two laser beams. The beat frequency may be used to maintain a predetermined offset frequency shift between the two laser beams. A modulator may modulate the first laser beam. The modulated first laser beam is to be injected into a device under test (DUT). A coherent receiver may acquire a backscattered signal from the DUT. The backscattered signal results from the modulated first laser beam injected into the DUT. The coherent receiver may use the second laser beam as a local oscillator to determine Brillouin and Rayleigh traces with respect to the DUT based on the predetermined offset frequency shift.

An integrated system for detecting a red palm weevil (RPW), farm fire, and soil moisture includes an optical fiber configured to be extending to a tree, and a distributed acoustic sensor (DAS) box connected to the optical fiber. The DAS box is configured to process first to third different optical signals reflected from the optical fiber, to determine a presence of the RPW from the first optical signal, a temperature at a location along the optical fiber from the second optical signals, and a moisture at a location around the tree from the third optical signal.

An optical fiber sensing system according to the present disclosure includes an optical fiber (10), a reception unit (21) configured to receive, from the optical fiber (10), an optical signal including an environment pattern indicating a state of an environment in proximity to the optical fiber (10), and a detection unit (22) configured to detect an occurrence of a power outage, based on a change in the environment pattern.