Fiber optic ribbon interconnect cable

#The present invention relates to a fiber optic cable for use in a cable assembly comprising fiber optic connectors connectorized to a ribbon in the cable.

#Electrical and fiber optic components are used to transmit data signals in telecommunication, computer, and closed circuit television systems. Conventional components, for example, opto-electrical and electro-optical transducers, are used in such systems to interface between electrical and fiber optic modes of signal transmission. Electrical systems, however, may experience crosstalk between the signal wires thereof. This type of electrical crosstalk occurs due to electromagnetic fields surrounding the transmitting wires. The electromagnetic fields due to one given circuit induce currents and electromotive forces in other circuits spaced close enough to the disturbing electrical circuit to be affected. For example, electrical crosstalk affecting a telephone line may result in the undesired mixing of caller conversations over the affected line. Spacing the electrical wires of different circuits apart tends to reduce electrical crosstalk. On the other hand, because optical-based systems use confined light as the information carrying medium rather than electricity, optical-based systems are not as susceptible to crosstalk and therefore do not require a significant crosstalk type spacing between the optical fibers.

#Opto-electrical and electro-optical transducers generally require electrical wires to be spaced apart sufficiently enough to avoid crosstalk. For convenience, respective ends of optical fibers in single fiber cables are connected to such transducers by placing them in housings comprising spaced fiber receiving apertures. Another method is to use a two-fiber optical ribbon with a 250 .mu.m spacing between the fibers whereby the fibers are separated, stripped, and individually connectorized. Both of the foregoing conventional methods are relatively expensive in respect of installation and material costs because two fibers must be individually connectorized.

#FIG. 1 shows a fiber optic cable assembly including a fiber optic cable according to the present invention.

#FIG. 2 shows a cross section of a fiber optic ribbon of the fiber optic cable of FIG. 1.

#FIG. 3 shows a cross section of the fiber optic cable of FIG. 1 taken across line 3--3.

#Referring to FIGS. 1-3, an optical cable 50 according to the present invention, for use in a fiber optic cable assembly 10, will be described. Fiber optic cable assembly 10 comprises conventional single fiber connectors 80 and 82, a conventional dual fiber connector 84, and a fan-out housing 86. Single fiber connectors 80 and 82 may be of the FC Ultra PC type made by the SIECOR.TM. Corporation of Hickory, N.C. Dual fiber connector 84 is of the type used to interface with, for example, an opto-electrical or electro-optical transducer (not shown). Dual fiber connector 84 is a conventional connector, for example, as disclosed in U.S. Pat. No. 5,214,730, which is hereby incorporated by reference herein in its entirety. Fiber optic cable 50 comprises a fiber optic ribbon 20. Ribbon 20 includes optical fibers 24, a variable spacing section 23, and a transition section 27 inside connector housing 86. Optical fibers 24 are spaced at a nominal fiber-to-fiber distance, herein defined as spacing S. Variable spacing section 23 comprises sub-carrier sections 22a and 22b comprising plastic tubes, e.g. furcation tubing, the spacing of which is variable.

#Each carrier section 22 includes an optical fiber 24 with a core and a cladding layer 26 therearound. Cladding layer 26 is surrounded by a protective coating 25. Protective coating 25 is surrounded by an identification ink layer 27. A separation layer 28 is strategically disposed between ink layer 25 and a peelable ribbon matrix layer 29. Separation layer 28 comprises a suitable material, for example, a TBII.TM. or silicone based material. Matrix layer 29 comprises, for example, a UV curable acrylate material or any suitable thermoplastic material, e.g. a PVC material.

#Matrix layer 29 constrains fibers 24 to spacing S. The nominal fiber-to-fiber distance defined by spacing S advantageously comprises an integer multiple of the nominal outside diameter (OD) of the fiber, for example, spacing S would nominally be 500 .mu.m, 750 .mu.m, 1000 .mu.m, or etc. The 750 .mu.m spacing would permit ribbon 20 to be connectorized to a conventional four fiber connector (not shown).