A fibre optic cable structure (300) suitable for fibre optic sensing with an improved sensitivity to an environmental parameter is described. The structure (300) includes an optical fibre (301) and a bend inducer (304) responsive to the environmental parameter to control bending of the optical fibre. The bend inducer (304) is configured to adopt a first configuration, that induces a first curvature of the optical fibre, at a first value of the environmental parameter and to adopt a second configuration at a second, different, value of the environmental parameter that induces a second, different, curvature of the optical fibre. By action of the bend inducer (304) a change in value of the environmental parameter imparts a bending force on the optical fibre.

A magnetic field sensor in the form of a multi-material optical fiber is described. The magnetic sensing optical fiber of the present disclosure can leverage optics and magnetostriction to sense an external magnetic field adjacent to the fiber. The magnetic sensing optical fiber can be customized to achieve various desired sensing sensitivities for various applications, including measuring while drilling and unconventional oil and gas applications. In one example, an optical fiber can include a cladding that can extend from a first end to a second end of the optical fiber. The optical fiber can further include an optical core within the cladding. The optical core can extend along the optical fiber between the first end and the second end. The optical fiber can also include a magnetostrictive element within the cladding. The magnetostrictive element can extend along the optical fiber between the first end and the second end.

An electric monitoring optical fiber package for an electrical monitoring sensing system is described, the system is used for monitoring and adjusting the electric or magnetic properties of an electric system or cable. The optical fiber package comprises at least one optical fiber, a portion of the optical fiber being coated with a coating material selected from the range of; electrostrictive material, magnetostrictive material, polarisation sensitive material, piezo-electric material; wherein the coating material is a polymeric material. The coated portion of the optical fiber is arranged to provide at least one sensing portion; the sensing portion comprising a sensing portion diameter. The invention aims to provide a low-cost, simpler electrical monitoring sensing system capable of sensing disturbances and anomalies in an adjacent electric system or cable.

An optical magnetometer comprising: an optical resonator having a central void; and a magnetostrictive material located in the central void such that a change in dimension of the magnetostrictive material causes a change in mechanical modes of the optical resonator. Also a method of making the optical magnetometer.

A sensor (1, 2, 3, 4, 5, 6, 7, 8) comprising a first diamond substrate (9) with at least one color center (15), the sensor (1, 2, 3, 4, 5, 6, 7, 8) further comprising a first piezomagnetic (10) or piezoelectric primary element (11), which primary element (10, 11) is arranged to interact with the color center(s) (15) of the first diamond substrate (9).

A fiber optic sensor system for measuring electric currents, such as the associated with geomagnetic disturbances and electromagnetic pulses. A fiber optic sensor system is disclosed including at least one light source, one or more first optical fibers having a first end arranged to receive light from the light source(s) and transmit the light to at least one of the sensor, and one or more second optical fibers arranged to receive reflected light from the fiber optic sensors and transmit the reflected light to a light sensing element. Using the sensors and the system, it is possible to measure currents within a structure of interest, such as upon the grounded neutral of an electric power transformer, take multiple measurements of current at the same piece of equipment or at multiple locations, or measure current and other physical phenomena on separate materials or structures.

This application relates to methods and apparatus for monitoring power cables (100) carrying multiple AC phases to detect deformation of the power cable. A distributed fibre optic interrogator unit (302) is used to interrogate a sensing optical fibre (301) coupled to the power cable to provide a measurement signal from each of a plurality of longitudinal sensing portions of the sensing optical fibre. An analyser (602) is configured to analyse the measurements signals to detect a characteristic of an imbalance in magnetic fields. The characteristic may be a signal component with a characteristic frequency related to the power frequency and number of AC phases, the sensing optical fibre may be sensitised to magnetic fields and the characteristic frequency may be 2n times the power frequency where n is the number of phases, e.g. six times the power frequency for three phase AC.

A method and apparatus for magnetic sensing is described. The apparatus includes a strain-sensing fiber coupled to a conducting strip. The strain-sensing fiber may be, for example, a distributed feedback fiber with Bragg gratings. A current may be induced to flow on the conducting strip by electrically coupling a photodiode to the conducting strip and then activating a laser optically coupled to the photodiode. In the presence of a magnetic field, a Lorentz force will be exerted on the conducting strip, causing a displacement of the conducting strip that will induce strain on the strain-sensing fiber. The strain on the strain-sensing fiber may be measured by laser-pumping the strain-sensing fiber and measuring the reflected waves. The measured strain may be used to calculate the magnitude of the magnetic field. Multiple strain-sensing fibers may be optically coupled in series and deployed into a borehole for distributed magnetic field measurements. The magnetic field measurements may be used to determine the resistivity of formations surrounding the borehole and, for example, to monitor the movement of relatively-low resistivity water fronts.

An optomechanical oscillator for measuring a magnetic field may include a fixed substrate, a moveable mass separated from the fixed substrate by a slot, a photonic crystal comprising an optomechanical cavity formed at the slot, and a current source operably coupled to provide current to the photonic crystal. The moveable mass may be moveable responsive to placement of the optomechanical oscillator in a magnetic field based on interaction of the magnetic field and the current. The magnetic field may be measureable based on displacement of the moveable mass.

A sensor system structured to measure an environmental property. The device includes a housing with shock absorbers disposed within and a laser cavity network. The laser cavity network includes one or more laser cavity arms, each having a gain chip configured to generate a laser beam and a means for locking a wavelength of the laser beam. The laser cavity network further includes a sensing material disposed within the laser cavity network, configured to accept the one or more laser beams of the one or more laser cavity arms and measure the environmental property in response to the plurality of laser beams. The system further includes a supply and control subsystem communicatively connected to the laser cavity network such that the supply and control subsystem is external to the housing, comprising a laser pumping source.