A data telemetry system and method digitizes acoustic sensor data. Acoustic sensor data is digitized and used to apply strain to a series of Fiber Bragg Gratings (FBGs) in a fiber. Each FBG is assigned a nominal wavelength. A wavelength interrogator launches wavelengths into the fiber and scans the reflected wavelengths from the FBGs. A data telemetry rate of at least 5 kHz may be achieved. Acoustic sensors may be part of undersea acoustic sensing arrays with large element counts having reduced system cabling and improved Size, Weight and Power (SWaP). The system and method realizes low power loss per array element and efficient multiplexing of many data streams in a small form factor.

A method of optical sensing is disclosed. The method comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal; coupling the backscattered signal into a second optical fiber, spatially separated from the first optical fiber; and optically amplifying the backscattered signal in the second optical fiber, thereby generating a sensing signal.

An apparatus (32) includes an electronic circuit (76, 80, 84), an electro-acoustic transducer (60) and a coupler (64). The electronic circuit is configured to receive data to be transmitted over an optical cable (24), and to convert the data into a modulating signal. The electro-acoustic transducer is configured to convert the modulating signal into an acoustic wave. The coupler is mechanically coupled to a section of the optical cable, and is configured to apply to the section a longitudinal strain that varies responsively to the acoustic wave, so as to modulate the data onto an optical carrier traversing the optical cable.

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.

This application relates to a fibre optic cable (104, 300) suitable for use with a distributed fibre optic sensor apparatus (106). The fibre optic cable includes at least one optical fibre (301) and a force transformer (304) mechanically coupled to the at least one optical fibre. The cable may also include at least one cladding later (302) and/or a compliant material (303). The cable may be surrounded by a jacket layer (306). The force transformer (304) is configured to transform transverse forces due to dimension changes of the cable arising from a temperature variation of the cable into longitudinal forces to counteract the longitudinal component of said dimension change over a tuned temperature range. In this way optical path length changes due to a change of temperature can be reduced or eliminated providing a cable which is insensitive to temperature.

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 fiber acoustic emission sensing apparatus and method including a laying device and an acoustic emission source; the laying device comprises base plate, first side plate and second side plate, the top portion of the first side plate connected with the top portion of the second side plate through an arc-shaped fiber-carrying channel, a main cavity formed by the first side plate and the second side plate; top portions of the first and second side plates respectively hinged with first and second arc-shaped covers, the lower end surface of the first arc-shaped cover fixedly connected with a first arc-shaped pressing body, the lower end surface of the second arc-shaped cover fixedly provided with a second arc-shaped pressing body, a first sensing fiber arranged under the first arc-shaped pressing body, and a second sensing fiber arranged under the second arc-shaped pressing body.

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.

A method of optical sensing comprises coupling an excitation optical signal into a first optical fiber to induce Rayleigh backscattering, thereby providing a backscattered signal. The backscattered signal is optically amplified in the first optical fiber, thereby providing an amplified backscattered signal. The amplified backscattered signal is coupled into a second optical fiber and is optically re-amplifying in the second optical fiber.

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.