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.

An optical fiber-based sensing membrane includes at least one optical fiber and a substrate. The at least one optical fiber is integrated in the substrate. The optical fiber-based sensing membrane includes, based on a specified geometric pattern of the at least one optical fiber, an optical fiber-based sensing membrane layout. The substrate includes a thickness and a material property that are specified to ascertain, via the at least one optical fiber and based on the optical fiber-based sensing membrane layout, a thermal property or a mechanical property associated with a device, or a radiation level associated with a device environment.

An optical fiber-based sensing membrane includes at least one optical fiber, and a substrate. The at least one optical fiber is integrated in the substrate. The substrate includes a thickness and a material property that are specified to ascertain, via the at least one optical fiber and for a device that is contiguously engaged with a surface of the substrate, includes the substrate embedded in the device, or includes the surface of the substrate at a predetermined distance from the device, a thermal property or a mechanical property associated with the device, or a radiation level associated with a device environment.

According to examples, an optical fiber-based sensing membrane may include at least one optical fiber, and a substrate. The at least one optical fiber may be integrated in the substrate. The optical fiber-based sensing membrane may include, based on a specified geometric pattern of the at least one optical fiber, an optical fiber-based sensing membrane layout. The substrate may include a thickness and a material property that are specified to ascertain, via the at least one optical fiber and based on the optical fiber-based sensing membrane layout, a thermal and/or a mechanical property associated with a device, or a radiation level associated with a device environment.

An interferometer apparatus for an optical fiber system and method of use is described. The interferometer comprises an optical coupler and optical fibers which define first and second optical paths. Light propagating in the first and second optical paths is reflected back to the optical coupler to generate an interference signal. First, second and third interference signal components are directed towards respective first, second and third photodetectors. The third photodetector is connected to the coupler via a non-reciprocal optical device and is configured to measure the intensity of the third interference signal component directed back towards the input fiber. Methods of use in applications to monitoring acoustic perturbations and a calibration method are described.

Force transducer (10) include two structural members (11, 12) spaced apart to define a gap (101) and being linked to each other. Optical fibers (13) are to the members and are freely suspended in the gap. The optical fibers are configured to provide a change in a detectable optical property responsive to a change in relative position between the two members in one or more predetermined degrees of freedom. Each of the optical fibers (13) is fixed to both structural members and continuous between the members to link the two structural members to each other. The optical fibers are substantially the only structure forming a link between the two structural members (11, 12), such that the arrangement of the optical fibers defines substantially the stiffness of the link between the two structural members in the one or more predetermined degrees of freedom, which stiffness is mainly, such as for at least 95%, determined by the optical fibers.

The invention is directed at an optical sensor device, comprising a sensing element for receiving an input action, an optical fiber comprising an intrinsic fiber optic sensor, and a transmission structure arranged for exerting a sensing action on the optical fiber in response to the input action received by the sensing element, wherein the optical fiber in a first connecting part thereof is connected to a reference body and wherein the optical fiber in a second connecting part thereof is to the transmission structure for receiving the sensing action, the first connecting part and the second connecting part of the optical fiber being located on either side of the intrinsic fiber optic sensor, wherein the transmission structure comprises a bi-stable spring having a first and a second stable deflection position and a negative stiffness range around an unstable equilibrium position between the first and second stable deflection position, and wherein the optical fiber between the transmission structure and the reference body is pre-stressed such as to be tensed, said optical fiber thereby acting as a spring having a first spring constant of positive value, wherein the optical fiber thereby counteracts a spring action of the bi-stable spring such as to operate the bi-stable spring in a deflection position range within the negative stiffness range, the deflection position range not including the unstable equilibrium position of the bi-stable spring.

This application relates to fibre optic cables structures which are particularly suited for use for distributed fibre optic sensing. A fibre optic cable structure (300, 500) is described which includes a cable core (301, 501) and a longitudinal strength member (302, 502). The cable core has at least one optical fibre (301a, 501a) and, optionally, one or more surrounding layers (505) and/or a strain transformer. (504) The cable core and is fixedly coupled to the longitudinal strength member at periodic fixed coupling points (303, 503). At the fixed coupling points the cable core has a substantially fixed position with respect to the longitudinal strength member and between the fixed coupling points the cable core is free to move with respect to the strength member. For an operating range of tensile load and pressure, the length (Lcoup) of the cable core between any two adjacent fixed coupling points is greater than the axial distance (Dcoup) along the fibre optic cable structure between the fixed anchoring points.

Apparatus and methods for fast quantitative measurement of perturbation of optical fields transmitted, reflected and/or scattered along a length of an optical fibre can be used for point sensors as well as distributed sensors or the combination of both. In particular, this technique can be applied to distributed sensors while extending dramatically the speed and sensitivity to allow the detection of acoustic perturbations anywhere along a length of an optical fibre while achieving fine spatial resolution. Advantages of this technique include a broad range of acoustic sensing and imaging applications. Typical uses are for monitoring oil and gas wells such as for distributed flow metering and/or imaging, seismic imaging, monitoring long cables and pipelines, imaging within large vessel as well as for security applications.

A fiber optic transducer is provided. The fiber optic transducer includes a fixed portion configured to be secured to a body of interest, a moveable portion having a range of motion with respect to the fixed portion, a spring positioned between the fixed portion and the moveable portion, and a length of fiber wound between the fixed portion and the moveable portion. The length of fiber spans the spring. The fiber optic transducer also includes a mass engaged with the moveable portion. In one disclosed aspect of the transducer, the mass envelopes the moveable portion.