JPH0616128B2 - Optical fiber cable manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method of making a submarine communication cable having optical fibers.

Coaxial submarine communication cables have been manufactured for analog telephone communication. These cables were manufactured to withstand some obvious environmental factors such as low temperature, high compressive force and corrosive water. In addition, submarine cables have been designed to withstand the high tensile and bending stresses encountered during cable laying and repair operations.

Advances in the field of optical fiber communication technology have made some practical optical fiber communication systems feasible. The features of these systems, such as digital format, wideband, and long repeater spacing, have made it possible to have relatively low cost per channel distance.
The potential for low cost makes submarine communication cables, including fiber optics, an attractive alternative to today's analog coaxial communication cables.

Heretofore, submarine cables containing optical fibers have been made from twisted steel wire isolated from a central single fiber by a core in which the fiber is embedded, as described, for example, in US Pat. No. 4,156,104. Was included.

Problems have arisen in manufacturing cables that include optical fibers for use in undersea communication systems. The measured loss of the optical fiber contained in the cable depends on the strain in the cable. Large variations in strain within the cable during cable manufacturing, laying, or operation of the cable system complicate the process of starting, laying, and operating the undersea communication system.

SUMMARY OF THE INVENTION This problem is solved by manufacturing an optical fiber cable by the process described below. The cable core containing the optical fiber is covered with an adhesive. Wrap a layer of steel wire around the adhesive on the cable core. A guide metal tube is formed to wrap around the layer of steel wire. Mold a metal tube onto a layer of steel wire.

DETAILED DESCRIPTION The present invention may be better understood by reading the following detailed description with reference to the accompanying drawings.

FIG. 1 shows a cross section 10 of a submarine communication cable including an optical fiber arranged for optical signal transmission. This cable includes a core 12, a stranded steel wire 13, a cylindrical conductor tube 14,
And an insulation and protective jacket 16.

As shown in FIG. 2, the cable core includes a central elongated reinforcing member or kingwire 18 and an elastomer 22.
It includes an optical fiber 20 embedded therein and a polymer jacket 23 surrounding an elastomer.

As shown in FIG. 2, the central elongated stiffening member or kingwire 18 is used for the core 1 and the core 1 during the cable manufacturing process.
It is a wire rod having a circular cross section that gives strength to No. 2. High strength copper clad steel is usually used. King wire 18 typically has a diameter of 0.8 millimeters. The minimum cross-sectional dimension of the kingwire 18 is determined by the tensile and flexural strength required during the cable manufacturing process. During the manufacturing process of the cable core, the king wire is mainly used as a reinforcing member. The core is manufactured in two operations. During each operation, the king wire is used to pull the completing core through various devices as the material is added in stages. After manufacturing the core, the cable is manufactured in two further operations.

Kingwire 18 is a coaxial cable device used for low frequency signal transmission of monitoring, maintenance, and control information while the fiber optic communication system is laid and operated on the ocean floor after the cable is fully constructed. Acts as the central conductor of. Due to this coaxial center conductor function, the king wire
The conductivity of electrolytic copper wire of the same size is at least 4
It is selected to have a conductivity of 0%.

In another device used in terrestrial communication systems that does not use signaling and operates at ambient temperatures that vary by much greater than the temperature of the ocean, in another device, the central elongated reinforcing member is made of high strength glass, especially epoxy or polyester. Such as a bundle of high strength glass embedded in a polymer such as.

Elastomer 22 is manufactured by EI du Pont
de Nemouro and Company) to HYTREL
Is an optical fiber encapsulant such as extruded cladding thermoplastic polyester that is marketed under the name of and is applied to the king wire 18 during the first core fabrication operation. Hytrel (HYTR
Further information describing the group of EL) polyesters is available at
Rubber Age 104, 3, 1972, pages 35 to 42 (Rubber Age, 104, 3, pages 35-42 (197
2); Proceedings of the in 1975 International Wire and Cable Symposium, pp. 292-299
ternational Wire and Cable Symposium pages 292-299
(1975); and Polymer Industrial Chemistry Vol. 14, No. 12, page 848-.
Page 852, published in December 1974 (Polymer Engineering
and Science, vol 14, No.12 pages 848-852 (December
1974)). The thermoplastic elastomer is
To protect the optical fiber inside the stranded wire near the center of the cable, it completely encloses several spaced optical fibers. In this device the fiber is located near the bending neutral axis of the cable. When the cable is in service, the seabed pressure is applied to the cable substantially symmetrically. The stranded steel wire equipment is designed to withstand seabed pressure with very small deformations. Since the elastomer completely surrounds each fiber in the core, the elastomer forms a buffer for isolating each fiber from any residual local loading caused by seabed pressure. As a result, the fiber microbends and the associated optical losses resulting from these microbends are minimized to seafloor pressure effects.

In the first core manufacturing operation, the king wire 18 is rewound from the pay-out reel at a controllable tension and a controllable speed. The king wire 18 is then straightened, washed with trichloroethane and heated. Two layers of thermoplastic elastomer 22 are applied to a hot king wire.

The first elastomeric layer in the plastic state is extruded directly around the heated kingwire. Some predetermined number, 6-12, of glass fibers are spirally laid over the first elastomer layer. The second elastomer layer is also extruded in an amorphous state. But the second
Of the elastomer layer is extruded directly around the first elastomer layer and the glass fiber. The second elastomer layer merges with the first elastomer layer between the fibers, thus completely enclosing each of the fibers with the elastomer.

The first core fabrication operation is completed by passing the semi-finished core through a water bath for cooling the core before winding the core onto a take-up reel.

In the second core fabrication operation, the outer surface of the elastomer is covered with a protective nylon jacket 23. This type of nylon used for the jacket is Nylon 6/12 Ditel 153 LNC10 (Z
ytel 153 L NC 10), which is supplied by Deupon. This sheath has a relatively high melting point of 213 ° C grade. The partially completed core is unwound from the reel, the nylon for the jacket 23 is heated to a plastic state and extruded directly over the elastomer 22. This jacket 2
3 completes the core, which is again passed through a pre-water tub for winding onto a take-up reel for cooling.

The elastomer 22 completely encloses the fiber 20 and the nylon jacket 23 encloses the elastomer 22 so that the fiber follows the elastomer and the nylon sheath when the cable is stretched.

Two additional steps are required to fabricate this finished core 12 into the cable 10 of FIG. The first of these tasks will be described with reference to Figures 2, 3 and 4. During the first cabling operation performed on the production line of FIG. 4, the core 12 was unwound from the payout reel 40, pulled through the dancer 41 and the guide 42, and named Eastman 148. Such is coated with the hot melt adhesive of FIG.

The adhesive application station 43 of FIG. 4 warms the adhesive 25 and thus coats the nylon jacket and removes some excess adhesive. In this station 43, the adhesive is heated in the range of 220 ° to 240 ° C. This temperature is
The adhesive is raised to flow over the nylon, a temperature high enough to completely cover the nylon but too low to damage the core. The adhesive 2 is applied by means of a die for applying twisting in the station 43.
5 is applied to nylon 23 to a constant thickness, as shown in FIG.

After applying the adhesive to the jacket, apply two layers of stranded steel wire,
Place the adhesive over the cover. The amount of adhesive 25 is the third
It is selected to be sufficient to completely cover the jacket as shown and to be sufficient to almost fill the gap between the jacket and the wire of the first layer of stranded steel wire 13. . Do not completely fill this gap. The adhesive cures in a few hours. By hardening this adhesive, the nylon jacket 23
And a firm bond is formed between the inner layer and the stranded steel wire 13. This bond prevents creep and ensures that the fiber core follows the stranded steel wire during cable laying, cable repair, and service operations. The adhesive is chosen so that this bond will not come off during these operations.

Referring again to FIG. 1, the cylindrical outer conductor of the low frequency signal transmitting coaxial cable arrangement is formed by the stranded steel wire 13 and the cylindrical conductor tube 14, both of which are located outside the core.

The stranded steel wire comprises two layers of stranded wire of circular cross section.

The inner or first layer of steel strands comprises eight wires that directly envelop and contact the outside of the core. These eight wires are in close contact with one another in frictional contact and have approximately the same cross-sectional dimensions. This wire is located up to the first stage of the stranded wire device 45 in FIG. 4 and forms a cylindrically shaped pressure retainer in which the wire twisted along the surface without crushing the cylinder. Continuously pushing each other.

The twisted steel in the cable is also the second
It includes an outer or second layer of 16 steel wires located over the inner strand to the step. These 16 steel wires include those of large diameter and those of small diameter, as shown in FIG. They lie against each other and in continuous frictional contact with the inner stranded wire. These wires in the second layer form an additional cylindrically shaped pressure retainer, which also holds the inner layer of wires in place. The first and second layers of steel twist are, as shown in FIG.
It is mated with the adhesive coated core by means of a closing die 47. The semi-finished cable containing the core, the adhesive and the two layers of steel strands is cleaned in a bath of trichloroethane 48 before being confined to a conductor tube.

The non-breathable cylindrical conductor tube 14 of FIG. 1 is formed directly over the outer layer of steel wire. The air-impermeable cylindrical conductor tube 14 is formed of a soft electrolytic copper welded seam tube. This high conductivity tube has (1) a more direct current path to power electronic repeaters that are spaced along the cable, (2) a moisture barrier for the fiber, and (3) In connection with steel wire, there is provided a cylindrical outer conductor for the aforementioned low frequency transmission system.

During the production of the cable in the production line of FIG. 4, the high conductivity annealed copper tape 50 is washed and slit into a certain width in the longitudinal direction, and is tubularly cut around the steel strand by a chopping device and a tube forming and rolling device 51. Wrapped in shape. The tube is sized to fit loosely over the steel strands so that the ends of the tape contact, leaving a gap between the steel and the wrapped material. After passing through the tube forming and rolling apparatus 51, both ends of the tape are welded together in the cylindrical conductor tube 14 by the continuous seam welding apparatus 53. Immediately, the conductor tube is swept and stretched through the embossing and rolling device 55 onto the outer steel strand, and within the clearance between adjacent wires in the outer steel strand as shown in FIG. Push some copper into. The molding of this copper into the outer clearance of the second layer of steel allows the steel strand package to be used especially during cable handling operations.
It is a guarantee that it will be kept in a cylindrical shape. Molding copper under the steel wire creates a contact area between each wire and the copper, which preserves the cylindrical shape of the strand and ensures that the steel and copper follow during subsequent handling. .

After the copper conductor tube 14 has been molded in place, the extending cable travels through another wash tank 57 for final cleaning with trichlorethylene. During the process, the cable now travels through dancer 58 and is wound onto take-up reel 60.

Then, in an isolated operation, the insulating jacket 16 shown in FIG. 1 is extruded so as to cover the cylindrical conductor tube 14 of copper material. The jacket is made of low density, natural polyethylene. During this polyethylene extrusion process, the cable containing steel strands and the cylindrical conductor tube of copper material are heated to a temperature high enough for the polyethylene to bond with the copper. The polyethylene is heated to a plastic state in the temperature range of 210 ° C to 230 ° C so that the polyethylene easily flows during extrusion. The temperature of the copper conductor tube rises to a minimum of 80 ° C. The bond formed between polyethylene and copper is strong enough to follow polyethylene and copper during cable laying, repair and system operation. This bond and the fit between the cylindrical conductor tube of copper material and the steel strand also follow each other with the polyethylene outer jacket and the steel strand. Since the jacket, steel strands and core all follow each other, the fiber is pulled like the other components of the cable. Since the fibers are proof tested to 2 percent strain, they are able to withstand strain during cable laying and repair operations without breaking. Optical loss in the fiber changes only slightly with changes in tensile strain in the cable. The change in optical loss within the fiber does not change much more than the change in loss caused by conventional cable designs. For suitable optical fibers, see IEEE Proceedings of the IEEE, pages 1280-81 S, September 1974, pp. 1280-81.
eptember 1974); Technical Paper of International Conference on Integrated Optics and Optical Fiber Communication, Digest of April 26, 1981 (Digest of Tech Papers, International Conf)
erence on Integrated Optics and Optical Fiber Comm
unications, page 26, April 1981); Ciel El
E-O 1981 Paper W6 6-1, June 1981 (CLE
O 1981, pager W6 6-1, June 1981); and April 1982, IEEE Journal of Quantum Electron Optics, QE-18, Vol. 4, pp. 504 to 510 (IEEE Journal of Quan
tum Electronics Vol.QE-18, No.4 pages 504-510, April
1982). The optical loss in the fiber changes significantly less with changes in tensile strain in the cable than changes in loss in the fiber made in the conventional way in the cable. FIG. 5 shows how the optical loss in the fiber changes with strain in the cable. Solid line 6
2 represents the change of the optical loss characteristics of the fiber in the cable cable arranged according to the present invention. The optical loss is approximately 0.01 decibel per kilometer at 0.5 percent strain. Dotted line 64 shows the change in fiber optical loss in a known cable arrangement. Line 6
4 shows the change in optical loss of the conventional design, which is approximately 0.10 decibel per kilometer at 0.5% strain. The optical loss due to strain can be reduced by a new design method that allows the cable components to follow each other and suppresses a slight bend caused separately by the strain in the cable.

[Brief description of drawings]

1 is a cross-sectional view of an embodiment of a communication cable including an optical fiber; FIG. 2 is an enlarged cross-sectional view of the core of FIG. 1; FIG. 3 is some reinforcement of the core and the cable of FIG. FIG. 4 is an enlarged cross-sectional view of a part of a member; FIG. 4 is a schematic side view of a manufacturing line for manufacturing a fiber optic fiber cable for communication; and FIG. 5 is an optical loss of a fiber in a cable manufactured according to a conventional process. 3 is a graph showing a comparison of the optical loss of a fiber in another cable made in accordance with the process disclosed herein, as a function of tensile strain in the cable. [Explanation of symbols of main parts] Cable core …… 12 Optical fiber …… 20 Adhesive …… 25 Stranded steel wire …… 13 Conductor tube …… 14 Elastic material …… 22 Outer sheath …… 23

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Robert Franklin Gleason United States 07728 New Jersey Shih Monmouth Freehold Portage Drive 58 (72) Inventor Don・ Aldrichch Hadfield United States 03862 Newhampshire-Rotkingham North Hampton Post Road 71 (72) Inventor Jyon Smith Berri Logan Giunia United States 03820 Newhampsiya -Strafdo-Dower-Berami-Road 38 (72) Inventor Alfrett Joji Richard Richardson United States 07747 New Jersey Monmouth Aberdeen Land- Le Way 610 (56) Reference References JP-A-57-104910 (JP, A) JP-A-56-66806 (JP, A) JP-A-56-164308 (JP, A)

Claims (3)

[Claims] 1. A method of making an optical fiber cable containing reinforced steel wire, the step of coating a cable core containing optical fiber with a curable adhesive; a plurality of reinforcements on the adhesive coating prior to curing of the adhesive. Winding a twisted steel wire layer made of steel wire and filling a gap between the outer surface of the core and the inner surface of the twisted steel wire layer with the adhesive; a conductor tube covering the twisted steel wire layer And a step of forming the conductor tube on the twisted steel wire layer and pressing the inner surface of the conductor tube so as to be in close contact with the outer surface of the twisted steel wire. 2. The manufacturing method according to claim 1, wherein the outer surface of the cable core is a nylon material,
The method of claim 1, wherein the nylon material is coated with a hot melt adhesive, and the adhesive is applied to the cable core in a temperature range of 220 ° C to 240 ° C. 3. The manufacturing method according to claim 1, wherein the adhesive is applied on the cable core with a constant thickness, the thickness of which is the same as that of the steel wire layer and the steel wire layer. A method of making characterized in that it provides an amount sufficient to fill most of the gap with the surface of the cable core.