Fibre optic cables

A fibre optic cable structure comprising:

• an optical fibre;
• and
• a bend inducer that is responsive to an environmental parameter to control bending of the optical fibre, wherein the bend inducer comprises:
• a first component with a longitudinal dimension that varies with the environmental parameter;
• and
• a second component with a longitudinal dimension that varies with the environmental parameter;
• wherein the amount of variation in the longitudinal dimension of the first component to a given change in the environmental parameter differs from the amount of variation in the longitudinal dimension of the second component to the given change in the environmental parameter;
• wherein the bend inducer is configured to adopt a first configuration at a first value of the environmental parameter that induces a first curvature of the optical fibre 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 such that a change in value of the environmental parameter imparts a bending force on the optical fibre,
• wherein at least one of the first or second components of the bend inducer comprises a plurality of elements adjacent to one another along a longitudinal direction, with at least some of the plurality of elements being moveable with respect to one another in a transverse direction, and wherein the elements are shaped such that relative transverse movement of an element with respect to its neighbouring elements changes the configuration of the elements and results in a change in a distance between the elements.

A fibre optic cable structure comprising:

• an optical fibre;
• and
• a bend inducer that is responsive to an environmental parameter to control bending of the optical fibre;
• wherein the bend inducer is configured to adopt a first configuration at a first value of the environmental parameter that induces a first curvature of the optical fibre 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 such that a change in value of the environmental parameter imparts a bending force on the optical fibre,
• wherein the bend inducer is configured such that a given change in the environmental parameter results in a positive change in a longitudinal dimension on a first side of the bend inducer components and a negative change in longitudinal dimension on a second, opposite side of the bend inducer, wherein the bend inducer comprises:
• a plurality of first elements fixedly coupled to a first surface at a first end and coupled to one another by resilient arms at a second opposite end;
• and
• a plurality of second elements, each second element being located between two first elements and supported by the resilient arms, such that transverse force applied to the resilient arms causes the second element to move transversely with respect to the first surface;
• wherein the first and second elements are shaped such that relative transverse movement of a second element with respect to its neighbouring first elements results in a change in the distance between the first elements.

A fibre optic cable structure comprising:

• an optical fibre;
• and
• a bend inducer that is responsive to an environmental parameter to control bending of the optical fibre;
• wherein the bend inducer is configured to adopt a first configuration at a first value of the environmental parameter that induces a first curvature of the optical fibre 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 such that a change in value of the environmental parameter imparts a bending force on the optical fibre, and wherein the bend induced is arranged along a helical path within the fibre optic cable structure.

A fibre optic cable structure comprising:

• an optical fibre;
• and
• a bend inducer that is responsive to an environmental parameter to control bending of the optical fibre;
• wherein the bend inducer is configured to adopt a first configuration at a first value of the environmental parameter that induces a first curvature of the optical fibre 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 such that a change in value of the environmental parameter imparts a bending force on the optical fibre, and
• wherein the fiber optic cable structure further comprises a plurality of bend inducers, wherein at least some the bend inducers are configured to induce curvature of the optical fibre in different planes to one another.

A fibre optic sensing system comprising:

• a fibre optic cable structure comprising:
• (i) an optical fibre;
• and (ii) a bend inducer that is responsive to an environmental parameter to control bending of the optical fibre;
• wherein the bend inducer comprises:
• (a) a first component with a longitudinal dimension that varies with the environmental parameter;
• and (b) a second component with a longitudinal dimension that varies with the environmental parameter;
• wherein the amount of variation in the longitudinal dimension of the first component to a given change in the environmental parameter differs from the amount of variation in the longitudinal dimension of the second component to the given change in the environmental parameter, wherein the first component and second component are configured such that a given change in the environmental parameter results in a positive change in the longitudinal dimension for one of the first or second components and a negative change in the longitudinal dimension for the other of the first or second components, and wherein the bend inducer is configured to adopt a first configuration at a first value of the environmental parameter that induces a first curvature of the optical fibre 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 such that a change in value of the environmental parameter imparts a bending force on the optical fibre;
• and
• an interrogator unit for interrogating the optical fibre with electromagnetic radiation to provide fibre optic sensing.