Fiber optic plenum cable

Claim 1

A fiber optic cable comprising a plurality of optical fibers, a buffer layer of elastomeric material surrounding and in intimate contact with each of said optical fibers to protect the fiber from radial stresses over a predetermined temperature range, a serving of nonburning material around each of said buffer layers, a jacket of relatively rigid polymeric material which has low smoke-producing, low flame-spreading properties surrounding said serving, a plurality of strength members of rigid, nonburning material for increasing the strength and rigidity of the cable and formed of material having a coefficient of thermal expansion of between about 0.2×10 -6 and about 15×10 -6 cm/cm/°C., said strength members controlling the thermal expansion characteristics of said cable, each strength member being surrounded by a jacket of relatively rigid polymeric material which has low smoke-producing, low flame-spreading properties, and an outer tube of low smoke-producing, low flame-spreading material bundling said jacketed optical fibers and said jacketed strength members, compressing the same against each other so that each jacketed optical fiber engages at least two jacketed strength members, whereby said strength members act to thermally stabilize said optical fibers, said cable having a flame-spread of 1.52 meters or less, a maximum optical density of 0.5 or less and an average optical density of 0.15 or less as measured in the UL 910 Steiner Tunnel smoke and flame test.