Cables

Cables can be electrical, fiber optic, or a combination of the two. Underwater electrical cables date back to the advent of the telegraph the mid 1840’s. Hemp, tar, and jute was used around conductors. The advent of plastics and other synthetic materials brought about a variety of new cable designs. The components of a typical underwater electrical cable are:

Conductors - the metallic component of cables through which electrical power or electrical signals are transmitted.

Insulation - material applied around a conductor to provide electrical isolation.

Strength member - bears tensile load, ensuring that it does not transfer to the conductors. Internal strength members are made from various polymers. External strength members, referred to as armoring, are usually made from steel wire.

Jacket - outer polymer layer protecting the parts inside.

There are two basic types of fiber used: SingleMode (SM) and MultiMode (MM). SingleMode fiber is generally used where the distances to be covered are greater. There are generally five elements that make up the construction of a fiber-optic strand: the optic core, optic cladding, a buffer material, a strength material and the outer jacket. Underwater optic cables have a heavy outer jacket and/or armoring. Many designs protect the fibers by running through a flexible steel tube that is filled with a gel compound which cushions the fiber and impedes or blocks water penetration.

The optic core is the light carrying element at the center of the optical fiber. It is commonly made from a combination of silica and germania. Surrounding the core is the optic cladding made of pure silica . It is this combination that makes the principle of total internal reflection possible. The difference in materials used in the making of the core and the cladding creates an extremely reflective surface at the point in which they interface. Light pulses entering the fiber core reflect off the core/cladding interface and thus remain within the core as they move down the line.

For information on commercially available underwater cables click here.

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