A subsurface impact protection system for protecting an underground asset is provided. The protection system includes a subsurface polymer layer provided above the asset to prevent impact forces from reaching the asset. A sensor network is embedded in the polymer layer. The sensor network comprises optical fibers each including one or more fiber optic sensors. The optical fibers receive an input signal from a source and transmit it through the fiber. At the output end of the fiber is an optical detector that measures light properties of the output optical signal indicative of environmental conditions near the polymer layer. The sensor network transmits a signal including measured light or environmental parameters to a monitoring computing system. In some embodiments, the polymer layer includes a protective mesh made up of a plurality of high density polyethylene strands in a woven pattern. A method of protecting an underground asset is also provided.

An apparatus and methods of inspecting, analyzing, classifying, and/or grading quality of a transparent sheet using a data set of photoelasticity measurements, thickness measurements, segmentation specifications, measurement specifications and quality control specifications of the transparent sheet. A results measurement is calculated on a computing system, quality control specifications are applied to the results measurement allowing writing to the database and creating reports, sending results to an operator interface and machine control.

A multi-core fiber includes multiple optical cores, and for each different core of a set of different cores of the multiple optical cores, a total change in optical length is detected. The total change in optical length represents an accumulation of all changes in optical length for multiple segments of that different core up to a point on the multi-core fiber. A difference is determined between the total changes in optical length for cores of the set of different cores. A twist parameter and/or a bend angle associated with the multi-core fiber at the point on the multi-core fiber is/are determined based on the difference.

Waveguides, such as light guides, made entirely of elastomeric material or with indents on an outer surface are disclosed. These improved waveguides can be used in sensors, soft robotics, or displays. For example, the waveguides can be used in a strain sensor, a curvature sensor, or a force sensor. In an instance, the waveguide can be used in a hand prosthetic. Sensors that use the disclosed waveguides and methods of manufacturing waveguides also are disclosed.

The present invention relates to an optical connection device for optically connecting a first connector (42) of a first optical fiber device (44) with a second connector (46) of a second optical fiber device (48) along an optical axis, which comprises a plug part (40) having an elongated shaft (58) having a longitudinal shaft axis (62) and a lumen (60) extending through the shaft (58) along the shaft axis (62) for receiving the first connector (42), the plug part (40) further having a cap (64) at a first end of the shaft (58) which has an insertion opening (66) for insertion of the first connector (42) into the lumen (60), the opening (66) being aligned and communicating with the lumen (60), the plug part (40) having an optical window (68) having a solid body element (69), wherein the plug part (40) is at least in part deformable; and a clamp part (18), wherein the plug part (40) is configured to be at least partially inserted into the clamp part (18), and the clamp part (18) is configured to, when the plug part (40) is at least partially inserted in the clamp part (18) and when the first connector (42) is inserted into the lumen (60) of the shaft (58) of the plug part (40), exert a force onto the plug part (40) which deforms the plug part (40) upon tightening the clamp part (18) so as to clamp and hold the first connector (42) in position and orientation with respect to the optical axis.

Example embodiments include an optical interrogation system with a sensing fiber having a single core, the single core having multiple light propagating modes. Interferometric apparatus probes the single core multimode sensing fiber over a range of predetermined wavelengths and detects measurement interferometric data associated with the multiple light propagating modes of the single core for each predetermined wavelength in the range. Data processing circuitry processes the measurement interferometric data associated with the multiple light propagating modes of the single core to determine one or more shape-sensing parameters of the sensing fiber from which the shape of the fiber in three dimensions can be determined.

An optical fiber sensor includes an optical fiber. The optical fiber includes a cladding having a cladding refractive index, and a plurality of fiber cores embedded in the cladding and extending along a longitudinal axis of the optical fiber. The plurality of fiber cores include a first subset of at least one first fiber core and a second subset of at least one second fiber core. The at least one first fiber core has a first core refractive index different from the cladding refractive index and a first core radius in a direction transverse to the longitudinal axis. The at least one second fiber core has a second core refractive index different from the cladding refractive index and a second core radius transverse to the longitudinal axis. The second core refractive index and the second core radius differ from the first core refractive index and the first core radius such that a temperature sensitivity of the at least one second fiber core differs from the temperature sensitivity of the first fiber core.

A fiber includes M primary cores and N redundant cores, where M an integer is greater than two and N is an integer greater than one. Interferometric circuitry detects interferometric pattern data associated with the M primary cores and the N redundant cores when the optical fiber is placed into a sensing position. Data processing circuitry calculates a primary core fiber bend value for the M primary cores and a redundant core fiber bend value for the N redundant cores based on a predetermined geometry of the M primary cores and the N redundant cores in the fiber and detected interferometric pattern data associated with the M primary cores and the N redundant cores. The primary core fiber bend value and the redundant core fiber bend value are compared in a comparison. The detected data for the M primary cores is determined reliable or unreliable based on the comparison. A signal is generated in response to an unreliable determination.

An apparatus, and related method, relates generally to a fiber-optic sensing system. In such a system, fiber-optic sensors are in a rosette or rosette-like pattern. An optical circulator is coupled to receive a light signal from a broadband light source, to provide the light signal to the fiber-optic sensors, and to receive a returned optical signal from the fiber-optic sensors. A spectral engine is coupled to the optical circulator to receive the returned optical signal and configured to provide an output signal.

The present disclosure provides a device that accurately measures vibration at a designated position of a sensing fiber without using digital signal processing to compensate for distance fluctuation. Digital signal processing for correcting fluctuation of a measurement distance due to a frequency offset of a beat signal due to vibration, which is a measurement target, is simplified. In the present disclosure, vibration at a designated position of the sensing fiber is accurately measured without using the digital signal processing to compensate for the distance fluctuation. A spectrum analysis length of an electrical field E(τn) of backscattered light is set to be larger than a delay deviation N.sub.d due to frequency modulation caused by dynamic strain. An index of tolerance of vibration distribution measurement to the delay deviation N.sub.d is also clarified.