A microstructured optical fiber comprises a doped core region embedded in a cladding layer, and a plurality of longitudinal tubes, wherein a radial cross-section of the optical fiber comprises a central hexagonal portion comprising a plurality of holes arranged according to a hexagonal grid surrounding a core section. Each hole corresponds to a respective tube, within a hexagonal boundary of the grid, and the plurality of holes comprises holes of first and second types arranged in a biaxial mirror-symmetric configuration. The holes of the first type are arranged in two side holey structures comprising distinct sub-grids of the hexagonal grid, defined by respective outer boundaries corresponding to portions of the hexagonal boundary of the grid and respective inner boundaries. Outer tangential lines to the respective inner boundaries cross each other at the opposed side of the core with respect to the side of the respective side holey structure.

A fiber optic sensor may be provided comprising an optical waveguide having at least one first core and a cladding surrounding the first core, wherein the first core extends substantially over the entire length of the optical waveguide and at least one Bragg grating is introduced into the first core, wherein the Bragg grating has an elongated cross section, wherein the short semi-axis is smaller than the diameter of the first core and the center of gravity of the cross section of the at least one Bragg grating lies on the axis of symmetry of the optical waveguide. A method may be provided for determining torsion with such a sensor. A method for the production of such a sensor may be provided.

An optical fiber includes multiple optical cores configured in the fiber including a set of primary cores and an auxiliary core. An interferometric measurement system uses measurements from the multiple primary cores to predict a response from the auxiliary core. The predicted auxiliary core response is compared with the actual auxiliary core response to determine if they differ by more than a predetermined amount, in which case the measurements from the multiple primary cores may be deemed unreliable.

A measurement system may be enabled to detect properties within an enclosure based on information detected using optical fiber sensors. The measurement system may include an enclosure having at least one wall with an inside surface and an outside surface; at least one silica-based optical fiber comprising at least one functional optical fiber core and at least one cladding layer; at least one optical fiber interrogation member; at least one transducer arranged to output energy; a controller; and a processing element configured to communicate with the optical fiber interrogator and the controller. The silica-based optical fiber is associated with a wall of the enclosure. The controller is configured to control the optical fiber interrogator and the transducer. The processing element is configured to process information from the optical fiber interrogation member.

A fiber sensor includes an optical fiber configured for operation at a wavelength from about 800 nm to about 1600 nm. The optical fiber includes a cladding that is defined by a fiber outer diameter and a core that is surrounded by the cladding. The core of the optical fiber has a Rayleigh scattering coefficient, .sub.s, that is controlled by controlling a concentration of one or more dopants in the core. The Rayleigh scattering coefficient is tuned to be within a predetermined range of an optimum Rayleigh scattering coefficient for a given total length, L, of the optical fiber. The predetermined range is from about 70% of the optimum .sub.s to about 130% of the optimum .sub.s.

The present invention discloses an optical sensor device, comprising: an optical fiber; a transducer; and an intrinsic fiber optic sensor embedded in the optical fiber; wherein the transducer is arranged as to receive an input action and converting such input action into a proportional strain on the intrinsic fiber optic sensor being at least the transducer and the intrinsic fiber optic sensor enclosed by a housing being the housing filled either with a thermally-responsive substance or a pressure-responsive substance being such device characterized in that the substance is a substance whose viscosity is reduced by at least 70% upon the change from ambient conditions to working conditions.

A novel system and method for detecting a quench of a superconducting conductor and detecting abnormal behavior of a superconducting conductor using acoustic sensor technology in the coolant of a superconducting cable and/or magnet is disclosed. This system and method is not only limited to use for superconductors, but also may be used for any device disposed in liquid and gas. Acoustic sensors are installed along a coolant space of a superconducting conductor and monitor coolant conditions. By monitoring acoustic changes, temperature changes or coolant flow disruption can be detected very quickly by an acoustic sensor array. By disposition of the acoustic sensor array in a coolant flow channel, the acoustic sensor system can quickly detect a local condition, such as the thermal status (temperature) of a superconducting cable and magnet with precise spatial resolution.

Distributed acoustic sensing (DAS) system for quasi-coherent detection of at least one multi-frequency signal over an optical fiber, including a multi-frequency pulse generator, a circulator, a coherent detector and a processor, the pulse generator for generating at least one multi-frequency pulse train including at least two pulses each having a different frequency, the pulse train including a plurality of carriers, the coherent detector for receiving at least one backscattered signal from the optical fiber and the processor for quasi-coherent aggregation of the carriers in the backscattered signal, wherein the processor channelizes the backscattered signal into at least one complex signal for each frequency in the carriers and wherein for each complex signal, the processor respectively extracts at least one of an amplitude change and a phase change for each one of the carriers and selectively aggregates at least one of the changes for the carriers for determining if an event has occurred over the optical fiber.

It is disclosed a cable for an overhead power transmission line, the cable comprising: a first optical unit comprising a first metal tube housing at least one an optical fiber suitable for sensing strain, the at least one optical fiber in the first metal tube being a tight buffered optical fiber fixed to an inner surface of the first metal tube; a second optical unit comprising a second metal tube comprising one or more loose optical fibers suitable for sensing temperature; and an armor comprising one or more layers of metal wires. The first optical unit is surrounded by at least one layer of semi-conductive or conductive material electrically contacting the outer surface of the first metal tube.

A sensor assembly has a flexible body, and a plurality of fiber Bragg gratings (FBG) sensor inserted into the body, the FBG sensor includes an optical fiber extending in a length direction of the body and a plurality of lattices disposed in the optical fiber, a variation of a wavelength spectrum of light, caused by a variation of an interval of the plurality of lattices, is detected, and at least one of force information applied to the body and temperature information of the body is extracted together with refraction information of the body.