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.

A distributed Brillouin sensor system comprising a pump laser, a Brillouin sensor fiber, and a detector system is described. The pump laser is arranged so as to send a pump signal into a first end of the Brillouin sensor fiber, and the detector system is arranged to detect Brillouin backscattering from the Brillouin sensor fiber. The Brillouin sensor fiber is characterized by having a negative dispersion, and further by an effective area of the sensor fiber being less than or equal to 50 m.sup.2.

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.

The present disclosure is a shape measurement system including: a multi-core optical fiber in which four or more cores are disposed in a part other than the center of a cross section; a strain distribution measurement device configured to measure a strain distribution of each of the cores in a longitudinal direction of the multi-core optical fiber; and an analysis device configured to calculate a shape of the multi-core optical fiber by using the strain distribution of the multi-core optical fiber.

The present invention relates to a method of re-connecting a first optical fiber (12) with a second optical fiber (34), the first fiber (12) and the second fiber (34) each having a plurality of outer cores, comprising: (a) positioning a first end section of the first fiber (12) and a second end section of the second fiber (34) in proximity so as to be aligned with one another along a longitudinal axis of the first and second end sections in a current connection position including a current connection orientation, in which a current relative rotational angle between the first and second end sections about the longitudinal axis is not known with respect to a relative rotational angle between the first and second end sections in a registered connection orientation determined with respect to a coordinate system during a previous connection of the first fiber (12) with the second fiber (34); (b) optically interrogating the outer cores of the first and second fibers (12, 34) through the current connection position to receive optical signals from the outer cores; (c) modifying, from the optical interrogation of the outer cores, the registered connection orientation such that the first and second fibers in the current connection orientation including the current relative rotational angle between the first and second end sections about the longitudinal axis are correctly registered with respect to the coordinate system.

The invention relates to a fiber-optic sensor 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, wherein the sensor has at least one second core which is at least partly surrounded by the cladding, wherein the longitudinal extent of the second core is less than the total length of the optical waveguide and at least one Bragg grating is introduced into the second core. Furthermore, the invention relates to a use of the fiber-optic sensor.

The present invention relates to an optical fiber for an SPR sensor, characterized in that the optical fiber is comprised of a core layer and a cladding layer surrounding the core layer, and the cladding layer is doped with metal nanoparticles.

A sensor system includes a radiation source, an optical fiber, and a detection device. The radiation source is arranged to emit pulses of radiation. The optical fiber comprises a first end and a core. The first end is arranged to receive pulses of radiation output from the radiation source such that, in use, the pulses of radiation are coupled into the fiber. The core is arranged to support propagation of the pulses of radiation along the fiber. The core includes a plurality of reflectors each comprising a portion of the core having a refractive index which is different to the refractive index of adjacent regions of the core. Reflections of a pulse of radiation from adjacent reflectors output at the first end of the fiber are resolvable from each other in the time domain. The detection device is arranged to measure radiation output from the first end of the fiber and resolve radiation reflected at different locations in the core of the fiber.

The invention relates to a device for optical applications, which has an optical waveguide (10), to which a light source (11) can be connected. The optical waveguide (10) is designed in such a way that light emitted by the connectable light source (11) propagates along a light propagation axis (12). A wavelength-sensitive grating structure (13) in the optical waveguide (10) has detectors (20), which are arranged in such a way that the detectors absorb partial amounts of the light of the light source (11) that is scattered by the wavelength-sensitive grating structure (13). The grating structure (13) in the optical waveguide (10) is constructed of periodically arranged ellipsoid structural elements (14). The ellipsoid structural elements (14) have a different index of refraction than the material of the optical waveguide (10) surrounding the ellipsoid structural elements. The ellipsoid structural elements (14) have a longitudinal axis and a short axis, which are substantially perpendicular to the light propagation axis (12). Depending on the wavelength, partial amounts of the light scattered by the grating structure (13) are coupled out of the optical waveguide (10). The light hits the detectors (20). An absorbing or partially reflecting filter (30) is arranged between at least one of the detectors (20) and the optical waveguide (10). The detectors (20) have measuring elements for the intensity of the partial amount of the light that hits the detector (20) in question. An evaluation element is provided, which determines a wavelength from the intensity ratio of the plurality of detectors (20). The detectors (20) are arranged in such a way that the detectors either are arranged opposite each other on different sides of the long axes of the

Methods and systems using one or more distributed feedback (DFB) lasers for capturing changes in the lasing environment are disclosed. Specifically, a sensor for measuring a measurand, such as pressure or temperature, or changes in a measurand, includes a fiber with at least one core, at least one fiber laser cavity formed by a single fiber grating in the core, wherein the laser operates on at least two modes along at least part of its length. The DFB laser includes a section that is bent into a non-linear shape and at least one pump laser connected to the fiber laser cavity. When the DFB laser experiences a perturbation or measurand change that changes the spacing of the modes, a change in an RF beat note is generated. This beat note can then be measured and related to the measurand change.