At&t Bell Laboratories

At&t Technologies, Inc.

American Telephone & Telegraph Co., At&t Bell Laboratories

Other

Lucent Technologies Inc.

Andrew J Panuska

Parbhubhai D Patel

Manuel R Santana

Charles H Gartside

Michael D Kinard

Krishnaswamy Kathiresan

Mickey R Reynolds

Walter J Paucke

George Harry Webster

Robert B Sprow

Arthur G Vedejs

A family of low optical fiber count cables which contains either optical fiber bundles, buffered fibers, or ribbon fibers housed in a core tube whose inner diameter is optimized for a cable containing two buffered fibers. The unoccupied volume of the core tube is filled with a water blocking material and the exterior surface of the core tube is coated with a hydrophilic material applied directly thereto. The core tube is encased in a dielectric jacket or in a metallic jacket. The cables thus formed can be used in a composite cable which includes an electrically conducting cable, and two abutting cables are incased in an outer sheath or jacket, forming a FIG. 8 configuration.

Low fiber count optical cable

A steam-resistant optical fiber cable (20) includes a core (21) comprising a plurality of optical fiber ribbons (22,22) disposed within a tubular member (30) comprised of a high temperature resistant material. The tubular member is disposed within a hermetic sealing member (40) which comprises a metal of low electrochemical activity having a sealed seam. An outer jacket (50) is disposed about the hermetic sealing member and in a preferred embodiment is characterized by resistance to degradation in high temperature, high humidity environments. The core may be unfilled or filled with a waterblocking material and in a preferred embodiment, a waterblocking member is interposed between the tubular member and the hermetic sealing member.

Steam-resistant cable such as steam-resistant optical fiber cable

An optical fiber cable (20) ideally suited for aerial distribution use, for example, includes in a preferred embodiment at least one bundle (23) of optical fibers (25--25). The at least one bundle is disposed in a tubular member (30) which is made of a plastic material suitable for use in a relatively wide temperature range and which is enclosed by a sheath system (32). A predetermined excess length of fiber is caused to be disposed in the tubular member. The excess length of each fiber is such that it is sufficient to avoid undue strains on the fiber as the cable core is exposed to the elements and to forces imparted during handling such as during installation. On the other hand, the excess fiber length must not be so great as to result in undue curvature of the fiber or excessive interactive engagement of the fiber with an inner wall of the tubular member. As a result of the magnitude of the excess length of the optical fiber, the requirements which must be met by the sheath system are not as demanding as for prior art cables, thereby resulting in a significant reduction in cable diameter and weight.

Lightweight optical fiber cable

A totally dielectric cable includes a core (21) comprising a plurality of optical fiber transmission media (24--24). The core is enclosed by a core tube (34) which is made of a plastic material and water blocking provisions are provided within the core tube for preventing the longitudinal migration of water. A water blocking tape (44) may be provided in engagement with an outer surface of the core tube and a plastic jacket is extruded thereover. Interposed between the outer surface of the jacket and the core tube are two diametrically opposed pluralities (60--60) of strength members each of which may be made of glass fibers. At least one strength member (62) of each plurality is rod-like to provide compressive as well as tensile strength for the cable. The remaining strength members of each plurality are relatively flexible rovings (64--64) which supplement the tensile strength of the rod-like members. The strength members are disposed and have a stiffness modulus which are effective to minimize any tensile strain which is imparted to the rovings.

All-dielectric optical fiber cable having enhanced fiber access

An optical fiber cable (20) includes a core (21) comprising a plurality of optical fibers (24--24) without intended stranding. The plurality of optical fibers are enclosed in a common tube (34) which provides a predetermined packing density and which is substantially parallel to the longitudinal axis of the cable. In one embodiment, a waterblocking material (36) is disposed within the tube to fill the interstices between the optical fibers and between the fibers and the tube. The waterblocking material is such that its critical yield stress does not exceed about 70 Pa at 20.degree. C. and such that it has a shear modulus of less than about 13 KPa at 20.degree. C. The common tube is enclosed with non-metallic or metallic strength members and a plastic inner jacket and by another layer of strength members and by a plastic outer jacket. This arrangement is such that the cable may be manufactured and installed with optical fibers capable of moving within the cable structure to prevent undue stresses being imparted thereto which would cause unwanted microbending losses.

Optical fiber cable

An optical fiber cable core (20) which is sold to a cable manufacturer for oversheathing or for incorporation into electrical power aerial cables, for example, includes in a preferred embodiment at least one bundle (23) of optical fibers (25--25). The at least one bundle is disposed in a tubular member (30) which is made of a plastic material suitable for use in relatively wide temperature range. The core is manufactured to cause a predetermined excess length of fiber to be disposed in the tubular member. The excess length of each fiber is such that it is sufficient to avoid undue strains on the fiber as the cable core is exposed to the elements and to forces imparted during handling such as during installation. On the other hand, the excess fiber length must not be so great as to result in undue curvature of the fiber or excessive interactive engagement of the fiber with an inner wall of the tubular member. Also, the plastic material of the tubular member must be such that it responds linearly to the application of tensile forces up to a strain corresponding to the excess fiber length at a given temperature.

Optical fiber cable core

An optical fiber cable (20) includes a core (21) comprising a units a unit (22). The unit is formed by a plurality of optical fibers (24-24) which are assembled together without intended standing. The unit is enclosed in a tube (34) which provides a predetermined packing density and which is substantially parallel to the longitudinal axis of the cable. In one embodiment, a waterblocking material (36) is disposed within the tube to fill the interstices between the optical fibers and between the unit and the tube. The waterblocking material is such that its critical yield does not exceed about 70 Pa at 20.degree. C. and such that it has a shear modulus of less than about 13 KPa at 20.degree. C. The tube is enclosed with non-metallic or metallic strength members and a plastic inner jacket and by another layer of strength members and by a plastic outer jacket. This arrangement is such that the cable may be manufactured and installed with the optical fibers capable of moving within the cable structure to prevent undue stresses being imparted thereto which would cause unwanted microbending losses.

Optical fiber cable and methods of making

An optical fiber cable (20) includes a core (21) comprising at least one optical fiber (24) which is enclosed in a tubular member (34) and which includes a sheath system (40). The sheath system includes two strength members 42--42 which extend linearly longitudinally along the cable parallel to a longitudinal axis (29) of the cable. The strength members are enclosed in a plastic jacket (46). The strength members have predetermined relative tensile and compressive stiffnesses. The stiffnesses are such that the strength members are capable of withstanding expected compressive as well as tensile loading and are coupled sufficiently to the jacket to provide a composite arrangement which is effective to inhibit contraction and which controls the position of the neutral axis during bending while providing suitable flexibility. The strength members in a preferred embodiment are made of a metallic material such as steel and have tensile and compressive stiffness which are substantially equal to cause the plane of bending to extend through the strength members. In other embodiments, the core is filled with a waterblocking material, the tubular member is enclosed by a water absorbent tape and/or a metallic shield and metallic conductors may extend colinearly with the strength members.

An optical fiber cable (20) includes a core (21) comprising a plurality of units (22--22). Each unit is formed by a plurality of optical fibers (24--24) which are assembled together without intended stranding. The plurality of units are enclosed in a common tube (34) which provides a predetermined packing density and which is substantially parallel to the longitudinal axis of the cable. In one embodiment, a waterblocking material (36) is disposed within the tube to fill the interstices between the optical fibers and between the units. The waterblocking material is such that its critical yield stress does not exceed about 70 Pa at 20.degree. C. and such that it has a shear modulus of less than about 13 KPa at 20.degree. C. The common tube is enclosed with non-metallic or metallic strength members and a plastic inner jacket and by another layer of strength members and by a plastic outer jacket. This arrangement is such that the cable may be manufactured and installed with the optical fibers capable of moving within the cable structure to prevent undue stresses being imparted thereto which would cause unwanted microbending losses.

Optical fiber cable including a plurality of multifiber units within a

In the manufacture of a lightguide fiber cable (21) in which a lightguide fiber core (32) is loosely disposed in a composite sheath 40 it is important to control the ratio of the lengths of the core and sheath. A core which is shorter than the sheath and which follows a shortened path on a reel may be unduly strained when the cable is installed in the field. This problem is overcome by coupling the core to the sheath by a system (25) which includes a constant speed linear capstan (146) and a relatively large variable speed sheave (150) that is positioned between the linear capstan and a takeup reel (154). The coupling of the core to the sheath is accomplished on the sheave after the sheath is elongated between the linear capstan and the sheave. The coupling and the elongation cooperate to compensate for the inherent shortfall in core length which otherwise would occur when the cable is wound on a reel. As a result, when tension forces that have been applied to the sheath are reduced, the sheath, which includes strength members having a relatively high modulus of elasticity, recovers to its original length and the ratio of the length of the core to that of the sheath becomes a predetermined value.

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Buford, GA, United States of America

Andrew J Panuska