Optical fiber communications cable

Abstract

An optical fiber cable includes a first jacket, typically comprising a polyvinyl chloride material, a core member comprising at least one, typically .ltoreq.10, optical fiber(s), and a core wrap loosely surrounding the optical fiber(s). The optical fiber(s) typically is (are) slightly overstuffed. The cable further comprises three non-metallic strength members (or groups of strength members) completely embedded in the first jacket and coupled thereto. In cables containing three strength members, the coupling is typically characterized by a pull-out strength of at least 25, preferably more than 40, lbs/in of strength member. Each strength member comprises a multiplicity of impregnated filaments, preferably borosilicate glass filaments impregnated with a urethane. The preferred cable typically has a circularly symmetric cross section, with the three strength members, each of radius r.sub.s, disposed longitudinally, their axes a distance R from the axis of the first jacket, with R>1.155(r+r.sub.s) where r is the inner radius of the first jacket. In one embodiment of the invention, the voids between the optical fiber(s) and the core wrap is filled with a filling compound, e.g., a fire retardant grease composition. In another embodiment, the cable further comprises a metal member, e.g., a steel tape, that contactingly surrounds the first jacket, and a plastic, e.g., polyvinyl chloride, outer jacket that contactingly surrounds the metal member. The cable can advantageously be used in the local distribution network, including in external plant applications such as distribution or buried service cable, and indoor applications such as riser or plenum cable.