EP0941493A1

EP0941493A1 - Submarine cable joint with branching joint assembly

Info

Publication number: EP0941493A1
Application number: EP97911654A
Authority: EP
Inventors: Mohamad A. Amirkalali; Tat Chiu Lee; Timothy Alan Sochar
Original assignee: Tyco Submarine Systems Ltd
Current assignee: SubCom LLC
Priority date: 1996-10-25
Filing date: 1997-10-08
Publication date: 1999-09-15
Also published as: TW357275B; JP2002500778A; WO1998019190A1; AU4897097A

Abstract

A passive branching joint assembly includes a housing (20) for a fiber storage device (30). The housing (20) is attached at one end to an endplate (80, 120) which accommodates at least one terminal socket (100), and is attached at the other end to an endplate (80, 120) which accommodates at least two terminal sockets (100). Fiber optic cables (190) are attached at the terminating sockets (100) so that loads placed on the terminating sockets (100) are transferred through the endplates and housing (20), rather than to the fiber storage device.

Description

SUBMARINE CABLE JOINT WITH BRANCHING JOINT ASSEMBLY

Field of the Invention The present invention relates to the field of submarine fiber-optic communications systems and, in particular, to a passive branching joint assembly for connecting three or more fiber-optic cables together.

Background of the Invention

In our truly global society, more and more people are becoming interconnected with one another through telecommunications systems.

Although submarine fiber-optic cable communications systems are but one type of telecommunication system, submarine fiber-optic cables are capable of carrying a greater number of data and voice transmissions than traditional submarine cable systems or modern satellite communication systems.

Stretching thousands of miles across the oceans, submarine fiber-optic cables lie on the ocean's floor, thousands of feet below sea level. Because no one cable could be made that extended thousands of miles in length, submarine fiber-optic cable communication systems are comprised of a series of submarine fiber-optic cables that are spliced together at cable joints. In this manner, many individual cables can be connected to form a single cable of the required length.

If one were to cut open a standard "non-armored" fiber-optic cable, he would see that each cable is comprised of a series of optic fibers clustered around a steel "king" wire. Together, these wires form the fiber-optic "core" of the cable. The fiber-optic core itself is surrounded by steel strength members and two watertight, insulating jackets (an inner copper jacket and an outer polyethylene jacket) encase the entire assembly. The function of the optic fibers is to carry the data and voice transmissions sent over the fiber-optic cable; the steel wires in conjunction with the insulating jackets, carry any loads placed upon the cable and give the cable its rigidity.

A cable joint is used to connect two or more cables together. Traditionally, two-cable joints were formed by "terminating" the two cables in separate terminating sockets and connecting the two terminating sockets with a load-bearing fiber storage tray or cylinder. The individual optic fibers of the cables were then spliced together and secured in the storage tray and the entire subassembly was then covered with a steel jacket and "insulated" to keep it waterproof.

Cable terminating technology is well-known in the prior art. The idea behind cable terminating is to secure the load-bearing steel members of the fiber optic cable, including both the steel strength members and the steel king wire, to a terminating socket so that any load placed upon the steel members would be transferred to the terminating socket. The fragile optic fibers of the cable, however, would completely pass through the terminating socket.

In one method of terminating cables, the steel strength members are terminated by stripping off the cable's protective insulation, separating the strength members from the fiber-optic core, and slipping the steel members and the core through the center of the terminating socket. A copper jacket and a steel plug are then placed over the fiber-optic core and the steel plug is firmly wedged into the terminating socket. In this way, the steel strength members are secured against the interior surface of the terminating socket, while the fiber-optic core passes freely through the socket. To terminate the steel king wire, the individual optic fibers are separated from the king wire and the king wire is attached to a king wire clamp. Because the king wire clamp is also connected to the terminating socket, or is connected to a load-bearing fiber storage tray that is attached to the terminating socket, the end result of these two processes is that all load-bearing steel members of the fiber-optic cable are secured to the terminating socket.

At times, however, it is desirable to interconnect three or more cables using a branch joint assembly. Such an arrangement will have at least one trunk cable and at least two branch cables. Typically, branch cable joints are assembled using a modified branching repeater body. Branch repeater bodies are designed for used in powered systems, but the associated electronics are unnecessary in unpowered systems. Thus, branching repeater bodies are typically modified for use in unpowered systems by removing the internal electronics. This practice is expensive and time- consuming. Thus, there exists a need for a branch assembly specifically designed for use with branching fiber optic cable joints.

Summary of the Invention

The present invention is a passive joint assembly which includes a cylindrical housing attached at each end to an end plate. Each end plate has at least one opening to accommodate one or more terminating sockets. Disposed within the housing is a fiber storage device which may either be attached to the housing or "floating" within the housing (i.e., non-load- bearing). A fiber optic cable extends through and is attached to a corresponding terminating socket. At each terminating socket, a fiber optic cable is terminated; the cable passes through the end plate, enters the terminating socket, and the steel strength wires of the fiber optic cable are secured to the terminating socket. The king wire of each cable is attached to a corresponding king wire clamp attached to each terminating socket or to the fiber storage device. The individual optic fibers of the cables are then spliced together and secured in the fiber storage device. Thus, all loads placed on the individual cables are carried through the end plates and the cylindrical housing rather than through the fiber storage device.

Brief Description of the Drawings

FIG. 1 is a cross section of a passive joint assembly according to the preferred embodiment of the invention. FIG. 2 is a cross section of the passive joint assembly illustrated in

FIG. 1.

FIG. 3 is a radial cross section of the passive joint assembly of FIG. 1.

Detailed Description of the Invention

The present invention is a passive joint assembly for use with fiber- optic cables. Although the present invention may be used with both armored and unarmored cables, the preferred embodiment of the invention is for use with unarmored submarine fiber-optic cables.

As seen in Figs. 1 and 2, the passive joint assembly 10 includes a cylindrical housing 20 which accommodates a fiber storage device 30 within the housing. The housing 20 has a branch end 40 and a trunk end 50. The trunk end 50 of the housing 20 has a radially inward extending flange 60. The housing 20 is designed to withstand external hydrostatic pressures when the joint assembly 10 is placed on the ocean floor. In addition, the housing 20 is designed to withstand tensile and torsional loading when the cables are being deployed. The fiber storage device 30 can be a cylinder or a tray and has at least three king wire clamps 70 attached to corresponding terminating sockets 100. A branch end endplate 80 having two openings 90 to accommodate two terminating sockets 100 is securely attached with pins 137 to the branch end of the housing 40, as shown in FIG. 3. The branch end endplate 80 has a shoulder 110 which rests on the branch end of the housing 40. A trunk end endplate 120 having a single opening 90 to accommodate a terminating socket 100 is attached to the trunk end of the housing 50. The trunk end endplate 120 is threaded on its outer edge 125 and has a shoulder 130 that rests against the inner surface of the flange 60 of the trunk end of the housing. A threaded ring 135 is threaded over the trunk end endplate 120 and tightened to secure the trunk end endplate 120 against the flange 60 of the housing 20.

The fiber storage device 30 is attached to the endlates 80, 120 in an axially slidable manner by set screws (not shown). An o-ring 127 is disposed between the trunk end endplate 120 and the fiber storage device 30 to limit and cushion the motion of the fiber storage device 30 and to compensate for axial tolerance build-up. Each endplate 80, 120 is covered by a cover plate 140 which acts to make a more uniform surface for the joint assembly 10 to facilitate application of an insulating jacket 150. The insulating jacket 150 is applied to make the joint water-tight and to electrically isolate the joint from the surrounding water.

Each terminating socket 100 has a radially outward flange 160 at one end which prevents the socket 100 from being pulled out of the housing 20 through the end plates 80, 120. The terminating sockets 100 have a cylindrical passageway 170 that extends longitudinally through the socket 100 to a flared region 180. A fiber optic cable 190 is inserted through cylindrical passageway 170 of the terminating socket 100 and is attached to the terminating socket 100 by splaying the steel wires 200 surrounding the fiber optic core (not shown) and inserting a tapered copper jacket 220 and steel plug 230 over the core. The copper jacket 220 and steel plug 230 are then pushed into the flared region 180 of the terminating socket 100 so the steel wires 200 of the cable are secured between the surfaces of the flared region 180 of the terminating socket 100 and the jacket/plug 220/230. The king wire of the fiber optic cable 240 is then connected to a corresponding king wire clamp 70 which is attached to a terminating socket 100 and extends into the fiber storage device 30. Then the individual optic fibers of each cable (not shown) are connected in the desired manner. The spliced optic fibers are then stored in a fiber storage device 30.

As shown in FIGs. 1 and 2, once assembled, the passive joint assembly 10 is encased in a premolded, heat shrinkable insulating jacket 150 made of a material such as a polyolefin. The insulating jacket includes a branch end portion 252 and a trunk end portion 254. Each portion 252, 254 is premolded to generally complement a corresponding outer configuration of the passive joint assembly 10 and a portion of the attached cables 190. When each portion 252, 254 is placed over the passive joint assembly 10, the portions 252, 254 form an overlapped area 255 which is adhesively bonded together. In addition, the inner surfaces of the sections of the jacket portions 252, 254 which extend over a length of the cables 190 have a layer of adhesive (not shown) to bond the insulating jackets portions 252, 254 around the cables 190. In order to keep the insulating jacket portions 252, 254 in place during the heat shrink process, the inner surface of each jacket portion 252, 254 may have a radial lip 260 which fits into a corresponding radial groove 262, 264 on the outer surface of the endplate 80 and threaded ring 135, respectively. In addition, the radial grooves 262, 264 and radial lip 260 can be positioned such that the radial grooves 262, 264 are located along the outer surface of the endplates 80, 120, housing 20 or threaded ring 135.

In actual use, the passive joint assembly 10 may additionally include an external cylinder 270 surrounding the joint assembly 10, to which are attached a pair of bend limiting boots 280, 282, wherein the bend limiting boot 280 at the branch end is configured to accommodate at least two cables 190.

In the preferred embodiment of the invention, the terminating sockets, the pins, and the casing are all made out of high-strength steel. However, any suitable high strength material may be used.

Previously, strength terminations were attached directly to the fiber storage device, and this allowed easy splicing and storage of fibers. However, it was also required that the fiber storage device be load bearing. In the passive joint assembly of the present invention, however, it is not necessary that the fiber storage device be load bearing. Thus, the fiber storage device can be constructed from inexpensive, lower strength materials such as aluminum or plastic. When a heat-shrinkable insulating jacket will be applied, it is also important that the fiber storage device be made of a material which can withstand the processing temperatures for application of the insulating jacket.

The present invention permits various interconnections between the three or more cables. For example, a trunk cable can be joined to the branch end cables, or the branch end cables can be interconnected. Thus, connections can be made between any two or more cables.

In addition, although the configurations of the housing and endplates have been described relative to a specified branch or trunk end of the joint, it should be understood that these configurations may be reversed and used at the opposite ends of the joint, with appropriate modification of the endplates to accomodate the appropriate number of cables. Also, although the present invention has been described in connection with the use of a terminating socket, it is understood that various other strength terminations may be used such as crimped ferrules, epoxy terminations or other socket designs well known in the art.

Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the above-recited detailed description, wherein only the preferred embodiment of the invention has been shown and described. The description of the preferred embodiment is simply by way of illustration of the best mode contemplated for carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various respects, all without departing from the invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive.

Claims

What is claimed is:

1. A passive branching joint assembly for connecting ends of three or more fiber optic cables, comprising: a fiber storage device; a housing containing the fiber storage device, the housing having a first end and a second end, wherein the second end of the housing has a flange extending radially inward; a first endplate attached to the first end of the housing, the first endplate having a first shoulder which rests against the first end of the housing, and including two through holes, each through hole being sized to accept a terminating socket, wherein each terminating socket is connected to a king wire clamp that extends into the housing; a second endplate having a through hole sized to accept a terminating socket, and having external threads and a second shoulder extending radially outward, the second endplate being disposed against the flange of the housing so the outer surface of the second shoulder rests against the inner surface of the flange, wherein each terminating socket is connected to a king wire clamp that extends into the housing; a ring having internal threads, the ring being tightened on the second endplate to secure the second endplate against the housing.

2. A passive branching joint assembly for three or more fiber optic cables connected to a fiber storage tray through terminating sockets, the passive joint assembly comprising: an elongated cylindrical housing having a first open end and a second open end, the second open end having an inward radial flange with an interior surface; a first endplate, the first endplate being circular and having at least one hole capable of accepting a corresponding terminating socket, wherein one end of the first endplate has an outward radial ledge with a lower surface which rests on the first open end of the housing when the first endplate is disposed in the first open end of the housing; and a second endplate, the second endplate being circular and having at least one hole capable of accepting a corresponding terminating socket, wherein one end of the second endplate has an outward radial ledge with an upper surface which rests on the interior surface of the flange when the second endplate is disposed in the second open end of the housing, wherein the housing, first endplate and second endplate are in load transferring contact.

AMENDED CLAIMS

[received by the International Bureau on 23 February 1998 (23.02.98); original claim 2 amended; new claims 3-25 added; remaining claim unchanged (5 pages)]

2. A passive branching joint assembly for three or more fiber optic cables connected to a fiber storage tray through terminating sockets, the passive joint assembly comprising: a housing having a first open end, a second open end, and an elongated cylindrical body extending between the first open end and the second open end, the second open end having an inward radial flange with an interior surface; a first endplate, the first endplate being circular and having at least one hole capable of accepting a corresponding terminating socket, wherein

AMENDED SΗEET (ARTICLE 19) one end of the first endplate has a first endplate outward radial ledge with a lower surface which rests on the first open end of the housing when a portion of the first endplate is disposed in the first open end of the housing, such that a portion of the first endplate outward radial ledge is in longitudinal alignment with a substantial portion of the elongated cylindrical body of the housing; and a second endplate, the second endplate being circular and having at least one hole capable of accepting a corresponding terminating socket, wherein one end of the second endplate has a second endplate outward radial ledge with an upper surface which rests on the interior surface of the inward radial flange when a portion of the second endplate is disposed in the second open end of the housing, wherein the housing, first endplate, and second endplate are in load transferring contact.

3. The device as recited in claim 2, wherein the portion of the first endplate outward radial ledge is disposed outside the housing.

4. The device as recited in claim 2, wherein the upper surface of the second endplate outward radial ledge is in longitudinal alignment with, and is disposed between, the first endplate and the interior surface of the inward radial flange.

5. The device as recited in claim 2, further comprising: a threaded ring for securing the second endplate to the second open end of the housing.

6. The device as recited in claim 2, further comprising: a fastener for securing the first endplate to the housing, the fastener passing through the housing and engaging the first endplate.

7. The device as recited in claim 6, wherein the first endplate has a main body and a first endplate flange, and the fastener comprises a pin that engages the first endplate at the first endplate flange.

8. The device as recited in claim 7, wherein the first endplate flange extends from the main body of the first endplate at an approximately 90 degree angle from the main body of the first endplate.

9. The device as recited in claim 8, wherein a portion of the elongated cylindrical body proximal the first open end of the housing extends longitudinally along the first endplate flange.

10. A passive branching joint assembly for connecting the optic fibers of two or more fiber-optic cables, comprising: a housing having a first end, a second end, an inward radial flange proximal said second end, and a body extending between said first and said second ends; a first endplate secured to said housing at said first end of said housing, said first endplate being capable of receiving a first terminating socket; a second endplate having a shoulder that abuts said inward radial flange, said second endplate being capable of receiving a second terminating socket; a fiber storage device contained within said housing; and a threaded ring for securing said second endplate to said housing.

11. The device as recited in claim 10, wherein said shoulder is in longitudinal alignment with, and is disposed between, said first endplate and said inward radial flange.

12. The device as recited in claim 11 , wherein said inward radial flange extends from said body of said housing at an approximately 90 degree angle.

13. The device as recited in claim 10, wherein said first endplate is secured to said housing by a fastener.

14. The device as recited in claim 13, wherein said fastener engages said first endplate at a first endplate flange.

15. The device as recited in claim 13, wherein said fastener comprises a pin that passes through said first end of said housing and engages said first endplate.

16. The device as recited in claim 15, further comprising a watertight cover over said housing, said first endplate, and said second endplate.

17. The device as recited in claim 16, wherein said first endplate is capable of receiving exactly two terminating sockets.

18. A passive branching joint assembly for connecting the optic fibers of two or more fiber-optic cables, comprising: a first endplate having a shoulder, said first endplate being capable of receiving a first terminating socket; a housing having a first end and a second end, wherein said first end abuts said shoulder of said first endplate; a second endplate secured to said housing at said second end, said second endplate being capable of receiving a second terminating socket; a fiber storage device contained within said housing; and a fastener for attaching said first end of said housing to said first endplate, said fastener passing through said housing and engaging said first endplate.

19. The device as recited in claim 18, wherein said first endplate has a flange and said fastener engages said first endplate at said flange.

20. The device as recited in claim 19, wherein said flange and said shoulder form an approximately 90 degree angle.

21. The device as recited in claim 20, further comprising a watertight cover over said housing, said first endplate, and said second endplate.

22. The device as recited in claim 21 , wherein said fastener comprises a pin.

23. The device as recited in claim 22, wherein said housing has a body, and said shoulder is in longitudinal alignment with a substantial portion of said body.

24. The device as recited in claim 23, wherein said first endplate is capable of receiving exactly two terminating sockets.

25. The device as recited in claim 24, wherein said second endplate has external threads for engaging a threaded ring, said threaded ring for securing said second endplate against said second end of said housing.