Optical fiber cable having an improved filling material within its core

• Main Author: SHEU; JIM JENQTSONG
• Format: Patent
• Language: English
• Published: 18.05.1999
• Edition: 6
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

A cable 20 of this invention includes at least one core 22 comprising a plurality of coated optical fibers 25 and a filling material 26 which is disposed about the fibers 25. Typically, the fibers 25 and the filling material 26 are disposed within a tubular member 28 which is disposed within a sheath system 27. The sheath system 27 may include longitudinally extending strength members 30 in addition to a plastic jacket 32. The filling material made in accordance with the preferred embodiment of the present invention is one which comprises at least two different hydrocarbons as an oil constituent and/or two different fumed silicas as part of a thickening agent. The hydrocarbon(s) may be a synthetic oil such as polyalphaolefin, for example, or a mineral oil, or a combination of synthetic oils and/or mineral oils. The combination of oils is used to help low temperatures properties as well as better incorporate a gelling system which may include a copolymer. A copolymer is used mainly to reduce oil separation. Additionally, a combination of gelling agents such as mixtures of two different fumed silicas is used to build a more stable and desirable network structure in the filling material. The novel combination of oils and fumed silicas produces a filling material capable of passing EIA/TIA Standard FOTP-81, Compound Flow (Drip) Test for Filled Optical Cable, Section 8 up to 80 DEG C. and has a critical-yield stress of less than about 0.002 psi.