A method including the steps of providing a toothing having teeth with tooth flanks; measuring two or more teeth of the toothing, wherein the following steps are performed for each of the two or more teeth: measuring a segment of at least one tooth flank of the tooth, wherein the measuring is performed optically by an optical measuring device, extrapolating the measured segment to an extrapolated segment; and evaluating deviations of the extrapolated segments of the two or more teeth.

A method including the steps of providing a toothing having teeth with tooth flanks; measuring two or more teeth of the toothing, wherein the following steps are performed for each of the two or more teeth: measuring a segment of at least one tooth flank of the tooth, wherein the measuring is performed optically by an optical measuring device, extrapolating the measured segment to an extrapolated segment; and evaluating deviations of the extrapolated segments of the two or more teeth.

An intravascular or other 2D or 3D imaging apparatus can include a minimally-invasive distal imaging guidewire portion. A plurality of thin optical fibers can be circumferentially distributed about a cylindrical guidewire core, such as in an spiral-wound or otherwise attached optical fiber ribbon. A low refractive index coating, high numerical aperture (NA) fiber, or other technique can be used to overcome challenges of using extremely thin optical fibers. Coating and ribbonizing techniques are described. Also described are non-uniform refractive index peak amplitudes or wavelengths techniques for FBG writing, using a depressed index optical cladding, chirping, a self-aligned connector, optical fiber routing and alignment techniques for a system connector, and an adapter for connecting to standard optical fiber coupling connectors.

Aspects of the present disclosure describe Rayleigh fading mitigation via short pulse coherent distributed acoustic sensing with multi-location beating-term combination. In illustrative configurations, systems, methods, and structures according to the present disclosure employ a two stage modulation arrangement providing short interrogator pulses resulting in a greater number of sensing data points and reduced effective sectional length. The increased number of data points are used to mitigate Rayleigh fading via a spatial combining process, multi-location-beating combining (MLBC) which uses weighted complex-valued DAS beating results from neighboring locations and aligns phase signals of each of the locations, before combining them to produce a final DAS phase measurement. Since Rayleigh scattering is a random statistic, the MLBC process allows capture of different statics from neighboring locations with correlated vibration/acoustic signal. The combined DAS results minimize a total Rayleigh fade, in both dynamic fading and static fading scenarios.

A utility pole degradation detection system according to the present disclosure includes: a sensing optical fiber (10) laid on a plurality of utility poles (30); a receiving unit (201) that receives vibration information detected by the sensing optical fiber (10); an identifying unit (202) that identifies a natural frequency of each of the plurality of utility poles (30) on the basis of the vibration information; and an analyzing unit (203) that analyzes a degradation state of at least one utility pole (30) among the plurality of utility poles (30) on the basis of a natural frequency of each of the plurality of utility poles (30).

A downhole device for installation in a petroleum well, comprising a sensor, a controller and a power source. The device further comprises an acoustic speaker configured to output a sound signal from the downhole device to a fiber optic cable in the well.

An integrated anchoring structure of basalt fiber reinforced plastic (BFRP) bars for a reservoir bank slope includes: a plurality of BFRP anchoring bars, where each of the BFRP anchoring bars includes a plurality of BFRP bars bonded to one another, a lower steel casing pipe, an upper steel casing pipe and a steel strand bonded to an upper portion of the upper steel casing pipe and aligned with the BFRP bars, and a grating array temperature sensing optical cable, a grating array stress sensing optical cable and a grating array vibration sensing optical cable are bonded in each of the BFRP bars; a plurality of shear-resistant bricks distributed on structural planes; a pouring base arranged at a bottom of the anchoring borehole; and an anchoring section arranged at an upper portion of the pouring base.

An accelerometer structure, a method for preparing the accelerometer structure and an acceleration measurement method are provided. The accelerometer structure includes a substrate having a groove structure, a test mass, a plurality of nano-tethers, and a nano-photonic-crystal measurement unit. The test mass, nano-tethers, and the nano-photonic-crystal measurement unit are suspended above the groove structure. A nano-photonic-crystal resonant cavity is formed in the nano-photonic-crystal measurement unit, and an acceleration of the test mass is characterized by a resonant frequency of the nano-photonic-crystal resonant cavity. The present disclosure provides a photoelasticity-based opto-micromechanical accelerometer structure, which uses a cavity resonance tension sensor in a nano-photonic-crystal cavity to measure a tension of the nano-photonic-crystal resonant cavity. The tension is concentrated in the nano-photonic-crystal resonant cavity, which makes the measurement of the tension more accurate and the resolution higher. Photoelastic-optomechanical coupling is also increased due to the nano-photonic-crystal resonant cavity.

An accelerometer structure, a method for preparing the accelerometer structure and an acceleration measurement method are provided. The accelerometer structure includes a substrate having a groove structure, a test mass, a plurality of nano-tethers, and a nano-photonic-crystal measurement unit. The test mass, nano-tethers, and the nano-photonic-crystal measurement unit are suspended above the groove structure. A nano-photonic-crystal resonant cavity is formed in the nano-photonic-crystal measurement unit, and an acceleration of the test mass is characterized by a resonant frequency of the nano-photonic-crystal resonant cavity. The present disclosure provides a photoelasticity-based opto-micromechanical accelerometer structure, which uses a cavity resonance tension sensor in a nano-photonic-crystal cavity to measure a tension of the nano-photonic-crystal resonant cavity. The tension is concentrated in the nano-photonic-crystal resonant cavity, which makes the measurement of the tension more accurate and the resolution higher. Photoelastic-optomechanical coupling is also increased due to the nano-photonic-crystal resonant cavity.

Systems, and methods for automatically identifying an underground optical fiber cable length from DFOS systems in real time and pair it with GPS coordinates that advantageously eliminate the need for in-field inspection/work by service personnel to make such real-time distance/location determinations. As such, inefficient, error-prone and labor-intensive prior art methods are rendered obsolete. Operationally, our method disclosure involves driving vehicles including GPS to generate traffic patterns and automatically mapping traffic trajectory signals from a deployed buried fiber optic cable to locate geographic location(s) of the buried fiber optic cable. Traffic patterns are automatically recognized; slack in the fiber optic cable is accounted for; location of traffic lights and other traffic control devices/structures may be determined; and turns in the fiber optic cable may likewise be determined.