Gas Blocked Cables - A New Approach.

Cables which are capable of preventing gases passing through them in an axial direction have many applications in both industrial and nuclear environments. Typically, a cable includes a strength member, several optical elements and a single or double sheath gas permeation being prevented by a stable filling compounds, often elastomers, incorporated into the interstices. A new type of gas block construction is described whose simplicity allows it to be made in a single operation. Three basic elements are incorporated, a glass-reinforced plastic strength member, a multiplicity of fibre waveguides and a combined thermoplastic sheath and gas block. Since all elements are extruded directly into the sheath, the need for filling compounds is eliminated. A loose tube version for use where time of flight constraints apply is also described. Author