A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.

Optical polarization control devices that include two pairs of squeezing plates oriented in mutually perpendicular directions are described. Compressive forces exerted by the two pairs of plates onto an optical fiber can be configured for low polarization mode dispersion. Various methods and systems in which the polarization control devices can be employed are also described.

A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.

A thrust bearing for a vehicle includes an upper case that abuts against a vehicle body-side attaching portion and a lower case on which the upper case is provided so that the lower case is rotatable with respect to the upper case about an axial center AX of a piston rod used in a shock absorber of a suspension of the vehicle, characterized in that the thrust bearing further includes a load sensor for measuring a load vertically acting on the suspension.

An extended length of optical fiber having an offset core with an inscribed Bragg grating is used a distributed sensor in combination with an optical frequency domain reflectometer (OFDR) to enable measurement small-scale (e.g., sub-millimeter) contortions and forces as applied to the fiber. The offset core may be disposed in a spiral configuration around the central axis of the optical fiber to improve the spatial resolution of the measurement. A reference surface exhibit a predetermined texture (in the form of a series of corrugations, for example, that may be periodic or aperiodic, as long as known a priori) is disposed adjacent to a longitudinal portion of the sensor fiber. The application of a force to the combination of the plate and the fiber creates a local strain in the grating formed along the offset core of the fiber that results in a shift in the Bragg wavelength of the grating. Using ODFR measurement techniques, an analysis of the Bragg wavelength shift allows for a high resolution force measurement to be obtained.

An example method injects a source light into a sensor cavity body, configured with an optical path including first and second reflecting surfaces, and structured to change the optical path distance between the first and second surface in response to subject condition. Sensor reflection optical signals are received from the senor cavity body, with first reflection signals from the first reflecting surface and se second reflection signals from the second reflecting surface and routed to an interferometer with a first optical path to a first reflector and a second optical path to a second reflector. Interferometer reflector signals, including reflections of the sensor reflection signals from the first reflector and the second reflector are received and phase shift coupled into separate channel signals, including first channel signals, second channel signals, and third channel signals, mutually spaced with respect to phase. A computerized dynamic obtains dynamic measurement of the subject condition, through detecting changes in the optical path distance based on the first, second, and third channel signals.

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.

Disclosed is a force sensor, including: at least one measurement cell, each measurement cell being filled with a filling material in which at least one inclusion of a substance is embedded; for each cell, at least one light source arranged in order to illuminate the inclusion embedded in this cell; for each cell, a measurement system including at least one optical measurement point arranged in order to capture light originating from the inclusion embedded in this cell; for each cell, a unit arranged in order to convert optical signals originating from the measurement system of this cell to a signal representative of a force exerted on this cell, this signal being dependent on a movement of the inclusion embedded within the filling material of this cell.

An optical fiber sensor system includes a light source, a modulation unit, an optical coupler, a polarization separator, a first polarization controller optically coupled to the polarization separator, and a first detection unit that includes a first optical detector that receives the first component, converts the first component into a first electrical signal, and detects stress. The first polarization controller controls a polarization state of light input to the polarization separator so that the first electrical signal exhibits a first-order response to the stress.

A fiber optic cable assembly includes an elongate housing, a signal fiber placed inside the housing and extending longitudinally, and a plurality of sensing fibers placed inside the housing and extending longitudinally. The plurality of sensing fibers is placed around the signal fiber. Each of the plurality of sensing fibers carries a respective laser signal of a distinct frequency. The signal fiber carries one or more evanescent coupling signals responsive to the laser signals in the plurality of sensing fibers.