CA1212828A - Method and apparatus for assembling an optical fiber communication cable - Google Patents
Method and apparatus for assembling an optical fiber communication cableInfo
- Publication number
- CA1212828A CA1212828A CA000477200A CA477200A CA1212828A CA 1212828 A CA1212828 A CA 1212828A CA 000477200 A CA000477200 A CA 000477200A CA 477200 A CA477200 A CA 477200A CA 1212828 A CA1212828 A CA 1212828A
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- tubular member
- solder
- optical fiber
- seam
- strip
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Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for assembling an optical fiber communication cable. The apparatus includes means for forming a tubular member having a generally downwardly facing longitudinally extending seam.
The apparatus also includes a source of molten solder and a means for contacting the downwardly facing seam with the solder.
An apparatus for assembling an optical fiber communication cable. The apparatus includes means for forming a tubular member having a generally downwardly facing longitudinally extending seam.
The apparatus also includes a source of molten solder and a means for contacting the downwardly facing seam with the solder.
Description
13 ~ 3 4 -~B
METHOD AND APPARATUS ~OR ASSEMBLING AN OPTICAL
FIBER CC~IUNICATION CABLE
The invention disclosed herein relates to a method and apparatus for assembllng an optical fiber communication cable. The cable produced by the instant in~ention has utility in underground, undersea, and other communication applications.
The advent of optical fibers for use in communication applications has permitted construction of relatively small diameter cables. Generally, optical fiber communication cables are designed to provide all of the required electrical, optical, and physical functions within the smallest possible diameter. Additionally, it is desirable that the cable be constructed to have a relatively long uninterrupted length and good flexibility character-istics. ~urthermore, in undersea applications~ the cable has to withstand stresses induced by hydrostatic pressure, temperature, and sea action.
An optical fiber communication cable generally consists of several layers of appropriate plastic materials such as polyethylene, polyimide, polyamide, plastic filaments in an epoxy matrix, or other similar plastics encapsulating a strengthening layer within which a dielectric layer is used to protect ~n inner tube or cable core. This inner tube or cable core is frequently made of materials which allow it to be used as a tubular conductor. When used in undersea applications, the core often contains an appropriate polyethylene or other long chain plastic gel material to help position one or more glass optical fibers. Typical optical cable constructions are those shown and discussed in U.S. Patent Nos.
3,955,878 to Nowak, - =
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. ~2~ 13~4-;~
4,118g5~4 to Arnaud~ 4,146,302 to Jachimowicz, 4,201,607 to Rautenberg et al., 4,212,097 to Portinari et al., 4,239,336 to Parfree et al., 4,232~935 to Rohner et al., 4,257,675 to Nakagome et al., 4,275,294 5 to DaYidson, 4,278,835 to Jackson, 4,279,470 to Portinari et al., and 4,288,144 to Nakai et al., in German Offenlegungsschrift 2,507,649 to Tscharntke, in "Guidelines to the Design of Optical Cables'~ by Wilkins, presented at the Winter Annual Meeting, December 2-7, 10 1979 of the .4merican Society of Mechanical Engineers, in "An Electro-Optical Array Support Cable'7 by Wilkins, presented at the Winter Annual Meeting, November 16-20, 1~80 of the American Society of Mechanical Engineers, in "Recent Experience with Small, Undersea Optical Cables" by Wilkins, IEEE-EASCON, October, 1979, Washington, D.C., in ~1How Small Can an Electro-Optical Cable Be?" by Wilkins, International Telemetry Society Conference, San Diego, California, October 13-15, 1981 and in "Design and Performance of an Undersea, Single-Fiber, Multi-Repeater, Full Duplexg Electro-Optical Da~a Link", by-Wilkins et al., International Telemetry Conference, San Diego, California, October 13-15, 1981.
Various approaches for assembling these optical cables are known in the art. One approach places 25 optical ~ibers within a split aluminum tube. A copper C tube made from copper tape is then formed over the aluminum tube and fibers so as to provide a hermetic seal. Therea~ter, the copper tube ma~ be surrounded by a dielectric layer, a strength member layer, and a sheath. An alternatiYe to this approach surrounds the aluminum tube and optical fibers ~ith a copper tape layer, a dielectric layer, and a sheath. U.S. Patent No. 4, 239,336 to Parfree et al. is illustrative of these approaches.
In a second approach, a metal tube is manu~actured such as by extrusion or roll~ng o~er a metal strip.
The tube is slit open and one or more optical fibers are inserted into the t~be. If deslred, a void fillin~
gel may be inserted along with the fiber or fibers.
The tube is then squeezed shut and the slit permanently closed as by welding. The tube is finally surrounded by a dielectrlc layer, a loadbearing section, and an outer ~acket. IllustratiYe of this approach is "An Electro-Optical Array Support Cablel' by Wilkins and U.S. Patent No. ~,275,2~4 to Davidson. A similar approach is shown in U.S. Patent Nos. 4,212,097 and 4,279,470, both to Portinari et al.
Yet ano~her approach known in the art rolls an electrical conductor tube from à flat-tape stock of copper material. Prior to tube closure, the optical ( ~ 15 fiber or fibers and/or a ~oid filler or pressure buffer layer are inserted into the tube channel. The tube is then forced shut and permanently welded or soldered. Additional layers consisting of synthetic materials and containing high tensile strength materials may be used to cover the conductor tube. Illustrative of t~is type of approach are U.S. Patent Nos, 4,146,302 to Jachimowicz3 4,232,935 to Rohner et al. and 4,257,675 to Nakagome et al.
The fabrication of optical communication cables by these approaches has been hampered by an inability to ( get extremely long uninterrupted lengths of assembled cable. Furthermore, the tube has to be threaded ~ith one or more glass conductor rods or fibers whose diameter is approximately 1~2 mm. Frequently, kinking or breaking of one or more of ~he fibers occurs during threadingg resulting in non-usable cable. In addition, damage to the fibers may occur during the tube sealing operation. If. the fiber threading operation is successful, the problem of filling the tube with-the appropriate filler while maintaining the fibers in reasonable separation st~ll rem2ins.
-4- 13084-~B
It has been discoYered that when the cushioning material i9 present in the tubular conductor during the sealing operation, it sometimes flows in~o the seam being closed. This seepage of cushioning material into the seam can adversely affect the seal formed by soldering or welding. As a result, the tubular conductor does not ha~e the desired degree of hermeticity.
In accordance with the instant invention, there 10 -is provided an improYed method and apparatus for assembling an optical fiber communication cable. The method of assembly according to the instant invention comprises forming a tubular member from a strip of metal or metal alloy, sealing the tubular member, and t - 15 releasing into the sealed tubular member one or more optical fibers. By releasing the one or more optical fibers into the tubular member after the sealing operation has been completed, the likelihood of damaging the fiber or fibers is minimized.
More particularly, the method of assembly in accordance with the instant in~ention comprises pulling a strip of metal or metal alloy through a flu~ applying ! /
., ~
/
station and then through a die to ~orm a tubular member having a substant~ally square and tight seam.
After the forming operation, the tubular member is passed through a station for sealing the s~am. During the seam sealin~ operation, one or more optical fibers and~or a cushioning material are housed within a protective sheath located internally of the tubular m~er. me protective sheath substantially prevents the trans-~ission of heat from the sealing operation to the one or ~ore optical fibers and/or the cushioning material, prevents any cushioning material from adversely affecting the seam sealing operation, and in general, protects the optical fiber or fibers. After the - sealing of the se~m has been completed, the fiber or fi~ers and/or the cushioning material are released into the tubular member. In a first embodiment, the optical fiber or fibers are released into the tubular member downstream of the location where the cushioning material is released into the sealed tubular member.
In a second embodiment~ the optical fiber or fibPrs are released into the sealed tubular member simultaneousl~ with the cushioning material. ln a third embodiment, the optical fiber or fibers are released into the sealed tubular member without any ( 25 cushioning material.
If desired, the tubular member forming the core may be used as an electr~cal conductor for transmitting power. Alternativel~, the t~bular member may be used solely as a strength member.
After the core has been fabricated, it may be surrounded ~y one or more additional layers. The additional layer or layers ma~ comprise a dielectric layer, a loadbearing layer, and/or an outer covering.
The apparatus ~or assembling an optical fiber c~mmunication cable in accordance with the instant invention includes a capillary means or protective -6- 130~4-i~3 sheath for releasing the one or more optical fibers into the tubular member after the sealing operation has been completed. In a first embodiment, the capillary means comprises concentric chambers or passageways for inserting both a cushionlng material and the one or more optical fibers into the sealed tubular member. Preferabl~, one o~ the concentric chambers or passageways e~tends into the tubular member farther than the other. In a preferred embodiment, the capillar~ means inserts the one or more optical fibers ~nto the tubular member downstream of the location where the cushioning material is in~ected into the sealed tubular member. In a second embod~ment, the capillary means comprises a single ~-- 15 passageway or chamber for substantially simultaneously `-- inserting the cushioning material and the one or more optical libers into the tubular member. In a third embodiment, the capillary ~eans comprises a-single passageway or chamber for inserting one or more optical fibers into the sealed tubular member without any cushioning material.
- To substantially prevent the transmission of heat f~m the seam sea~k~ operation to the one or more fibers and~or the cushioning material, the capillary means or protective sheath is preferably formed from a material haYing a ' relatively low thermal conductivity. In addition, the capillary means or protective sheath should be formed from a material that will not be bonded to the tubular member by the means ~or sealing the seam and that can withstand the temperatures associated with the seam sealing. Suitable materials for forming the capillary means include high stainless steels, refractory alloys, ceramics and insulating materia-s. Alter-nati~ely, the capillar~ means may be formed from composite materials. The composite may comprise an -7- 13084-~B
outer material having a low thermal conducti~rit~ and an inner material havln~ a higher thermal conductivit~.
If desired, the'capillarg means ma~ be Joined to an external cooling system. By doing this, heat withln the capillary means may be readily withdra-~m.
The cable produced by the metAod and apparatus of the instant invention should ha~e a relatively small diameter and good flexibility characteristics. This cable should also be capahle of resisting sea action and of withstanding the pressures and temperatures associated with undersea applications. In addition, the ca~le produced by the method and apparatus of the instant invention is capable of being level ~ound on a storage reel, of being stored on a reel with a minimum ('; 15 total volume and of having relatively long uni~ter-rupted lengths.
It is an ob~ect of the present invention to provide a method and apparatus for assembling an optical fiber communication cable having a relatively small diameter.
-It is a further object of the present invention to provide a method and apparatus as above ~or assembling an optical fibe~ communication cable having a relatively relatively long uninterrupted length.
It is a further ob~ect o~ the present invention ( to provide a method and apparatus as above for assembling an optical ~iber communication cable ~a~ing a sealed tubular''core with a relatively high degree of hermeticity.
It is a further object of the present in~ention to provide a method and apparatus as abo~e for inserting one or more optical fibers into the tubular core after the sealing operation has been completed so that the risk of damage to the fiber or fibers are min~mized.
It is a further object o, the present invention to pro~Jide a method and apparatus as above for insertin~ a cushioning material about the fiber or fibers, if de-sired, without adversely affecting the sealing of the tubular core.
In accordance with a particular embodiment of the invention there is provided an apparatus for assembling an optical fiber communication cable.
The apparatus includes means for forming a tubular member by progressively deforming an advancing metal strip member, said means for forming having a generally downwardly facing longitudinally extending seam. The apparatus also includes a source of molten solder and a means for contacting the downwardly facing seam with the solder.
These and other objects will become more apparent from the following description and drawings.
Embodiments of the method and apparatus for assembling the optical fiber communication cable and the cable produced by the instant invention are shown in the drawings wherein like numerals depict like parts.
Figure 1 is a schematic representation in partial cross section of a side view of an apparatus used to assemble a first type of optical fiber communi-cation cable core having one or more optical fibers and a cushioning material.
Figure 2 is a schematic representation in partial cross section of a bottom view of a portion of the apparatus of Figure 1.
Figure 3 is a schematic representation in partial cross section of the apparatus used to fabri-cate the outer layers of an optical fiber communica-tion cable.
Figure 4 is a schematic representation in cross section of a first cable embodiment produced in accordance with the instant invention.
Figure 5 is a schematic representation in partial cross section of a side view of a second embodiment of an apparatus used to assemble an optical fiber communication cable core having one ,~
,, ,, ~
:~L~ 3 - 8a -or more optical fibers and a cushioning material.
Figure 6 is a schematic representation in partial cross section of an alternative embodiment of an apparatus for assembling an optical fiber communication cable core without any cushioning material.
Figure 7 is a schematic representation in cross section of an optical fiber communication cable core formed by the apparatus of Figure 6.
B~
-9- 13084-~B
In accordance with this ~n~ention, a method and apparatus for assembling an optlcal ~iber c~mmunication cable are provided. T~e instant method of assembly makes use of a tube form~ng technique to permit assembly of a cable having a core comprising a metal or metal alloy tubular me~er having a relatively small diameter and a relatively long uninterrupted length.
The cable produced by the instant method and apparatus should satisfy all electrical, physical, and operational constraints for underground, undersea, and other uses.
Furthermore, the instant method and apparatus permit production of a relatively small diameter cable ha~ing a core exhibiting excellent strength and ~lexibility characteristics~ The cable produced by the instant method and apparatus may ha~e a diameter substantially about one-quarter that of a conventional cable and a transportation Yolume substantially about one-tenth that of a conventional cable.
The method of assembling the optical fiher communication cable of the in~ant inventlon i5 relatively lnexpensi~e and simple to perform. The instant method readily solves the problem of forming, filling, and sealing a tubular member with ne~ligible risk to the fiber or fibers within the member. It also produces a tubular member that is substantially free of internal and external rough spots, both substantially circular and concentric, substantially clean on both the internal and external sur~aces before~ during, and after tube fabrication, and capable of being used as an elec~rical conductor.
Referr~ng now to Figures 1-3, an apparatus 10 is shown for assem~ling a first type of cable core ll that is particularly use~ul in undersea applications. The apparatus 10 takes a strip 12 of metal or metal alloy and forms it into a tubula~ member 14 by pulling the --10- 13084-~
strip through a forming die 16l The use of a die to form a tube from strip material is well known in the art. Manufacturing Proc-esses, Sixth Edition, by Myron L. 3egeman et al., John Wiley and Sons, Inc.-, 1957, pp. 283-285, discloses Yarlous dies for form~ng a tube out of strip ~aterial. Any suitable die arrangement may be utilized. Ho~ever, prior to passlng through die 16, strip 12 is passed through a fluxing statlon 15. Fluxing station 15 applies a flux to the edges of the strip 12. Fluxing station 15 may comprise any conventional means ~or appl~in~ any con~entional flu~ known in the art. Preferably, the tubular member 14 is formed ~ith a longitudinal seam 38 having square and tight edges 40. While the seam 38 may be formed on ~~ 15 any side, preferably seam 38 faces downwardl~. An~
sultable means such as a t~ke-up reel not shown may be used to pull strip 12 through flu-~ing station 15 and die 16.
After the tubular member 14 has been ~ormed by the die 16, it is passed to a station 42 for sealing the seam 38. .Statton 42 ma~ comprise any suitable sealing mechanism, i.e. soldering means;, welding means, brazing means, etc. known in the art. In a preferred arrangement, station 42 comprlses means for soldering the seam 38.
( A supply of solder is provided in a sump or bath 44. The solder is fed in a conventional manner, such as by a pump not shown, to a soldering head 46 having an orifice 47. The solder is preferably fed through the soldering head 46 and orifice 47 at a pressure suffic~ent to create a spout of solder. The tubul~r member 14 and the se~ 38 are passed over the spout o~ solder. The movement of the tubular member over t~e spout of solder and surface tension drive the solder into the seam interface formed by the edges 40.
The sold~r capillaries up into and substartially fills P~2~,~
~ 13084 I~
the seam 38. After the solder solidlfies; tne tu~ular member 14 is completely sealed~ B~ seallng the tubular member in this fashlon, the tubular member ~a~
be provided with a relatively high degree of hermeticity. Any suitable solder including silver solders, high-temperature solders, low-temperature solders such as lead-tin solder, lead-antimony solder, tin-antimony solder, etc., may be used to seal se~m 38 and tubular member 14.
10After passing over the soldering head 46, tubular member 14 passes over a wiping device 48 for removing any excess solder. Wiping device 48 may c~mprise a spring ~ipe or an~ o~her suitable wiping mechanism.
During the tubular member forming and sealing operations, at least one optical fiber 18 and a C~ cushioning material 30 are located within a protecti~Je sheath or capillary means 17. The tube ~orming operation preferably takes place about the protective sheath or capillary means 17. The capillary means 17 is intended to prevent damage to the at least one fiber 18 and cushioning material 30 from the sealing operation and to preYent the cushloning ma~erial from seeping into the seam and adversely affecting the sealing operation. A~ter the solder has soliaified and the tubular member 14 has been sealed, at least (one optical fiber 18 and a cushioning material 30 are inserted lnto the tubular member~ As used herein, the term inserted means released from the capillary ~eans-and deposited into the sealed tubular member.
3Q In a preferred embodiment of the instant inventlon, the cushioning material 30 is inserted into the tubular member 14 ~ust upstream of the insertion o~ at least one optical fiber 18 ~nto the tubular member The capillary ~eans or protective sheath 17 ~or insertlng the at least one optical fiber 18 and the cushioning material 30 into the tubular member 14 ~-12 130~4~
comprises a first chamber or passageway 20,through which the optical fiber'or ~ibers 18 pass and a concentric sec'ond chamber or passageway 32 for insertlng the cus~ioning materlal 30. Chamber or passageway 20 has a pressure seal 22 with an inlet opening 24 at a first end. The optical fiber or fibers 18 enter the ~assageway 20 through the opening 24. At the opposite end o~ passage~ay 20 is an outlet opening 26. Passageway 20 and outle~ 26 guide the optical fi~er or fibers 18 and deposit or release the fiber or fibers 18 into the tubular member 14 preferably after ~the solder has solidified and the tubular member has been sealed. One ad~antage to releasing the fiber or fibers 18 into the tubular ~ember after the sealing ~-- 15 operation has been completed is that the risk o~ damage `'' to the fiber or fibers as a,result of the sealing operation is minimized. In a preferred method of assembling th s type of optical fiber communication cable, the fiber or fibers 18 are inserted into the tubular member 14 downstream of the locatlon where the cushioning ma,terial 30 has been injected or inserted into the tubular member 14. Although any suitable ~echnique may-be used, fiber or fibers 18 are preferably deposited lnto tubular member 14 by pulling the fiber or fibers from one end by an~ suitable means not shown in any suitable manner.
In a preferred embodiment, the chamber or passagew-ay 32 for inserting cushioning material 30 into the't~bular me~ber concentrically surrounds the passageway 20. ~he cushloning material 30 enters the passageway 32 through an inlet opening 34, preferably whi-le under pressure. The passageway 32 has an outlet ,opening or e~it nozzle 36 through which the cushioning material 30 flows into the tubular ~ember. Passageway 32 e~tends a distance sufficient to insure that the cushioning material 30 does not ~lo~ into the tubular -13- 13~84-.~3 member until after.the solder has so~d~ied. By~,ralt ~
until after the solder has solldlfied and the tubular member 14 has been sealed to in~ect cushionlng material 30 into the tubular member 14, any risk of the cushioning material adversely affecting the sealing operation or vice-~ersa is minimlzed and an impro~ed seal may be effected. If cushioning mate~ial 30 were inserted before the sealing operation had been completed or before solder solidification, the cushioning material 30 could flow into the seam and ad~ersely affect the sealin~ operation by preventing the solder ~rom capillarying up into the seam interface.
The cushioning material 30 is preferably intro-- 15 duced into passageway 32 under pressure so that as the cushioning material 30 flows into tubular member 14, it substantially fills the tubular member 14 and substantially surrounds the optical fiber or fibers 18.
Cushioning mater~al 30 helps position the fiber or 20 fibers 18 wi.thin tubular ~ember 14. Any suitable mechanism not shown can be used to supply the cushioning material 30 under pressure to passageway 32.
The cushioning material 30 is in part caused to flow through opening 36 by the motion of tubular memoer 14 ,.- 25 and fiber or fibers 18. The mo~ement of t~bular member - 14 and fiber or f}bers 18 in the direction of arrow~A
creates a suction force on the cushioning material 30.
This suction force helps draw the cushioning material 30 through opening 36 and.into tubular member 14.
Although the cushioning material 30 may be introduced into passageway 32 in substantially any fo-rm and at substantially any desired temperature, it has-been found to be desirable to insert the cushioning material 30 into the passageway 3~ in a heated condition. This heated condition impro~es the flow-ability of the cushioning materlal 30 by making the . ~ .
-~4- 13084~
cus~ionlng material ~ore fluid. As a result of th~s lmpr~ved flo~ability, it is belieYed that the cushioning material can be drawn out of the nozzle 36 and into the tubular member at a lower suction force than that ordinar~ly required. Any suitable conventional heating device not shown ma~ be used to heat the cushioning material 30 either before or after it enters the passage~a~ 32.
In a preferred embod~ment of the capillary means 17, passagewa~s 20 and 32 are not coextensive.
Preferably, the outlets 26 and 36 are arranged so that the cushioning materlal 30 enters the tubul~ member 14 upstream of the location where the release of the optical fiber or fibers 18 into the tubular member (- 15 takes place.
If necessary, tubular member 14 may be passed through a die 50 for sizing the tubular member 14 to its exact desired dimension. Sizing die 50 preferably ~ comprises a sinking die. If a sizing die is utilized, the optical fiber or fibers 18 are preferahly inserted ~nto the tubular member just prior to or simultaneous with the tubular member 14 passing through the sizing die 50.
By inserting the cushioning material 30 and the f~ber or fibers 18 in the manner previously described, ~- it is believed that the magnitude of the forces required to lnsert t~e cushioning material 30 and the flber or flbers 18 into tubular member 14 may be reduced. ~y reducing these forces, the likelihood of damag~ng or klnking the optical fiber or fibers 18 during lnsertion is minimized.
In Figure 5, an alternative embodiment of an apparatus 80-for assembling the cable core 11 is shown.
As tn the embodment of Figures 1-3, a strip 12 of metal or ~etal alloy is pulled through a fluxing station 15 for applying a flux to the strip edges 40 --15- 1~084~
and then throu~h a die ].6 for ~ormlng the tubular member 14. The tubular member 14 is then passed o~r a station 42 for seallng the seam 38.
A~ter the tubular member has been sealed and the sealing material, i.e. solder, has solidified, the cushioning material 30 and the fiber or fibers 18 are inserted substantially si~ultaneously b~ the capill2r~
means or protective sheath 81. The capillary means 81 preferably comprises a single passageway 86 having a pressure seal-82 with an inlet opening 84 at a first end. The optical fiber or fibers 18 enter the passageway 86 through the opening 84. On a sidewall of the passageway 86, preferably adjacent the seal 82, an inlet opening 87 is pro~ided for supplying cushioning material 30 into the passageway 86. In a preferred arrangement, the pressure seal 82 and the inlet opening 87 are at a substantially right angle to each other. At the end of the passageway 86 opposed from pressure seal 82, an outlet opening 88 is proYided.
The passageway 86 extends a sufficient distance into the tubular member that the fiber or fibers 18 and the cush~oning material 30 are released into the tubular member 14 after the solder has solidified and the t1lbular member 14 has been completely sealed. As before, by waiting until after the solder has solidified and the tubular member 14 has been completely sealed to release the cushioning material 30 into the tubular member 14, any risk of damaging the cushioning material 30 or ad~ersely affecting the sealing operation by cushioning material 30 seeping into the seam 38 is minimized.
Wh~le any suitable technique may be used~ fiber or - fibers 18 are preferably deposited into tubular m~mber 14 by pulling the fiber or fibers 18 from one end by any suitable means no~ shown in any suitable manner.
~3 -16- 13084~
The cushion~ng material 30 is preferably inserted lnto passageway 86 while under pressure so that it substantially fllls the tubular member 14 and substantially surrounds the optical fiber or fibers 18.
The cushioning material 30 is also pre~erably inserted into passageway 86 in a heated condition so that ~he flo~ability of the cus-hioning material 30 is impro~ed.
It is desirable that the flowability of the cushioning material 30 be improved because while the fiber or fibers 18 mo~e at substantially the sane speed as the tubular member 14, the cushioning ~aterial 30 needs to flow at a greater speed since ~t has to fill the tubular member. It is also believed that this increased flowability also reduces the magnitude of the force needed to be exerted on the cushioning C mater~al to get it to flow into tubular member 14.
The cushioning material 30 is in part caused to flow - through the opening 86 by a suction force created by - the motion o~ tubular member 14 and fiber or fibers 18.
If a sizing die 50 need be used, outlet opening 88 is preferably located substantially near the location of the sizing die. Again, sizing die 50 preferably comprises a sinking die. By positioning the outlet opening 88 at this locationg it is believed that the magnitude cf the forces required to insert the ,- cushioning material 30 and the fiber or fibers 18 into tubular member 14 may be reduced.
For certain applications, it is not necessary to ha~e a cushioning material surround the optical fiber or fibers ~ithin the cable core. Figure 6 shows an alternative appara~us 100 for ~orming such a cable core 11'. The apparatus 100 is readily adaptable for inserting one or more optical fibers in an unconstrained condition into a closely surrounding tubular member.
-17- 130~4~
As ln the previous ~mbodiments, a strip 12 o~ the metal or metal alloy is pulled through a fluxi~g station 15 ~or applying a ~lu~ to the strip edges 40 and then through a die 16 for forming the tubular member 14. The tubular member 14 is then passed o~Jer a station 42 for sealing the sea~ 38.
After the tubular member has been sealed and the sealing material, i.e. solder, has solidified, the fi`oer or fibers 13 are inserted or released ~nto the tubular member by capillary means or protective sheath 102. The caplllary means 102 comprises a single passageway 108 having a seal 104 with an inlet opening 106 at a first end. The optical ~iber or fibers 18 enter the passageway 108 through the opening 106. At the end of the passageway 108 opposed to the seal 104 is outlet opening 110. The passageway 108 extends a -sufficient distance into the tubular ~ember that as the fiber or fibers 18 emerge from the opening 110, the fiber or fibers are released into the member 14 after t~e solder has solidified and the tubular member 14 has been com~letely sealed. The capillary means or protective sheath 102 minimizes the possibility of the sealing operation damaging the optical fiber or fibers.
While any suitable technique may be utilized, the fiber or fibers 18 are preferably deposited into tubular member 14 by pulling the fiber or fibers 18 from one end ~y any suitable means not shown in any suitable ~anner. If needed, apparatus 100 may be proYided with a sizing die not shown for providing 30. cable core 11~ with a.particular outer dimension.
It is desirable that the capillary means or protectiYe sheath 17, 81, and 102.be made from a - material having certain properties. First, the material should not be bondable to the metal or metal alloy forming member 14. If the material were bondabIe, the sealing operation could bond the 18- 13~84-~13 capillary means to the member 14. Second, the material should be able to withstand the temperatures associated wlth the sealing operation and, therefore, should have good high tem~erature properties. Finally, the material should have high strength characteristics and - should have a relatively low thermal conductivity. B~J
providing a material having a relatively low thermal conductivity~ tle or substantially none of the heat-created-during the sealing operation will be transmitted to the optical fi~er or fibers and/or any filler material. Suitable materials out of which the capillary means or protective-sheath may be ~abricated include refractory alloys such as high-nickel alloys, ceramic materials, high stainless steels, sapphire, insulating ~ype materials and composites comprising an ( - outer material having a relatively low thermal conductlvity and an inner material having a higher thermal conductivity than the outer material. It should be recognized that the aforementioned materials are exemplary and should not be limi~ing in an~ way.
O~her suitab~e materials ~ay be used.
In certain high temperature situations, it may be desirable to provide the capillary means or protective sheath with a cooling arrangement. In this way, each optical fiber and/or any cushioning material may be additionally protected from heat generated dur~ng the sealing operation. Cooling could be provided in any suitable con~entional manner. For example, the capillary means or protectiYe sheath could be connected to an external cooling apparatus 112. Cooling apparatus 112 may c~mprise any suitable conventional cooling apparatus known in the art. Cooling could be pro~ided to any or each passage~ay of the capillary means or protecti~e sheath. In situations where it is desirable to provide cooling, it ~ould be advantageous to form-the capillary means or protective sheath out of -]9- 13084-i~B
a composite material as discussed aboYe. The higher thermally conductive inner material could be connected to the cooling apparatus while the outer material performs its protective functionO
The cable core 11 or 11' may conta:in any desired number of optical fibers 18. In a preferred embodiment, one to six optical fibers are located within the cable core. Preferably, each optical fiber 18 comprises a photo-conductor glass rod; ho~ever, any suitable optical fiber may be used in the cable.
While any suitable technique may be used to deposit the fiber or fibers into the tubular ~ember 14, it is preferred to deposit the fiber or fibers by pulling from one end without applying any significant back tension. Since each fiber 1~ remains substan-tially unconstrained during the tubular member forming - operation, each fiber is under substantially zero tension at the same time that the tubular member 14, as a result of the core ~ormation process, is near maximum elastic tension. By doing this, it is possible to put each fiber in static compression after unloading so that an increment of plastic strain in the sheathing equal to the net static compression could be imposed without kinking the fiber or f~bers 18.
~lternati~ely, if desireda the optical fiber or fibers 18 may be helically wound within the cable core 11 or 11 r, Cushioning material 30 may comprise any suitable non-setting vo~d filler. The temperature to which the cushioning material is heated depends upon the selected filler and its ~iscosity characteristics. In a preferred embodlment, cushioning material 30 comprises a gel which is initially introduced into its passageway at a temperature in the range of about 35C to about 150C, preferably at about 100C.
3~
The use of cushioning material 30 is highly desirable in a cable which may be subjected to high bending or hydrostatic stresses. Cushioning material 30 has two primary functions. First, it lubricates the fiber or fibers 18 to prevent stiction and micro-bending. Second, it provides the fiber or fibers 18 with a hydrostatic, ambient pressure environment.
Strip 12 which is used to form tubular member 14 preferably has an initial width greater than the outside circumference of the tube formed by forming die arrangement 16. The initial width is about 5% to about 15%, preferably about 10%, greater than the tube outside circumference. By starting with such an initial strip, the seam 38 created dur-ing tube forming will be put into significant com-pression, thereby remaining substantially closed even if spring back occurs. If it is desired to form a mechanical interlock joint, the edges 40 of strip 12 may be shaped in any suitable manner so that a mech-anical seal is formed along seam 38 during tubeforming. -By using a strip 12 having such an initialwidth and pulling the strip through a forming die 16, the formed tube will be a drawn tube having a gener-ally longitudinally extending seam 38 defined byopposing substantially non-linear deformed edges whose length from the outside of said tube to the inside of said tube exceeds the thickness of the strip. These deformed edges are the inherent result of Applicants' forming technique. It should also be noted that the transverse cross-sectional area of the initial strip exceeds the transverse cross-sectional area of the formed strip tube.
- 20a -The extra volume of metal also inherently assists in the formation of a tube 14 having a rela-tively tight seam 38 without a notch or well at the outer periphery of the seam. Further, the edges defin-ing the seam 38 are inherently deformed by the tube forming technique described above to provide substan-tially non-linear and intermeshing edges not shown.
This results in an increase in surface area of the seam edges to which the sealing material can adhere as compared to the original strip 12 edges thereby improving the resultant strength of the seal. This - also results in better hermeticity than prior cable core assemblies.
The deformed intermeshing edges are the in-herent result of the processing in accordance with the above-described techniques and do not correspond to the shape of the original strip edges. The de-formed edges result from the drawing of the tube by the process of this invention.
In contrast, a tube formed by folding even with the use of a die forming technique would not have such deformed edges since in a folding operation the starting strip would not include the excess--material which the process of this invention uses to form the :
deformed edges. A deficiency of the folding technique is that a well or depression occurs at the outer sur-face along the seam. In accordance with this inven-tion, the presence of excess material from the metal i; strip causes the outer surface to form against the - 30 die so as to eliminate such well or depression along the seam. This is highly significant since it reduces the amount of solder or brazing material which would be required to provide a circular outer periphery to the resultant tube 14.
Z~
- 20b -The material comprising strip 12 and tubular member 14 should possess certain conductivity, strength, and thickness-to-diameter ratio characteristics. The material should possess a high electrical conductivity since member 14 preferably acts as a conductor in the final cable. In the cable system, tubular member 14 may be used to carry current between repeaters not shown which may be spaced about 25 km. apart.
Since member 14 is preferably the only metal component in the cable, the material should possess high strength properties. The material preferably possesses significant yield strength and a relatively high yield strain. The member should be formed from a material that has a yieId strength sufficient to keep the tubular member in a substantially elastic state for any degree of cable bendin~. By havlng a member that is maintained in a substantially elastic state and substantially never in a plastic state, the risk of breaking the glass fiber or ~ibers due to placing the glass fiber or fibers in tension is minimized.
A material having a relatively high yield strain is important since it reduces the overall cable diameter. The yield strain of the material forming the tubular member also dete~mines how much of the ultimate strength of an outer loadaearing layer can be used without permanently straining the tubular mem~er and breaking the optical fiber or fibers.
T~e material used to produce tubular member 14 should also be capable of sustaining certain coiling forces during fabrication and installation. Therefore, a thickness~-to-diameter ratio K which indicates good formabil~ty characteristics is required. If the material does not possess good formability character-istics, the tubular member ~all ma~ be crinkled or buckled during tube formation. I~ this occurs on the inner surface of the member, optical fiber or fibers 18 may suffer microbending against angular surfaces and large inc~eases in atten~ation may result.
A preferred strip material has a conductivity in the range of about 25 to 102~o IACS, a yield strength in the range of about 30 to about 90 ksi, preferably in the range of about 50 ksi to about 60 ksi, a yield strain in the range o~ about 0.0017 to 0.0095 and a thickness-to-diameter ratio of about 0~ 02 to 0.50. .
number of metals and alloys possess the required combination of strength, conductivity, and thickness-to-diameter ratio and may, there~ore, be utilized. -In a preferred embodiment, the material forming strip 12 and tubular member 14 comprises a copper/zirconium alloy, -22- 13084-;~
de~ignated CDA 15100, manufactured by Olin Corporation.
Copper alloy C15100 has a conductiYity o~ about 95~
IACS, a yield strength of about ~2 ksi, a yield strain OL about 0~0034 and a thickness-to-diameter ratio of about 0.15.
Since the strip is being pulled through a fluxing station, a forming die and/or a sizing die, a slightly harder material is desirable in order to avoid strip breakage. The material selected should haYe a hardness of at least about 1/4 hard. Copper alloy C15100 can be hardened to meet this requirement. In a preferred embodiment, copper alloy C15100 has a hardness in the range of about at least 1/4 hard to about spring. It has been found that a tubular member formed from copper alloy C15100 in this hardness range is particularly suitable for situations where an outer layer or layers is to be ~abricated about the cable core using high temperature fabrication techniques.
After cable core 11 or 11' has been assembled utilizing either apparatus 10, apparatus 80, or apparatus lOOj the cable core may be surrounded by one or more additional laye~. For examDle, dielectric layer 56 may ~e fabricated about the member 14. A typical cable will ha~e such a dielectric layer if the tubular member 14 is to be used as an electrical conductor.
Dielectric layer 56 may be fabricated in any suitable conventional manner using any suitable conventional apparatus. ~or e~ample, dielectric layer 56 may be extruded about the cable core by any suitable extruding arrangement 72 in a conventional manner. ~he dielectric layer 56 preferably comprises a high density polyethylene, although any suitable ~aterial -may be used. The dielectric layer preferably takes no part in system telemetry and acts only as an insulator.
However, ~f desired, it ma~ be designed to take part in the system telem2try. ~ tubular member 1~ is not -23- 130~4-~
used as an electrical conductor, the d~electric la~;er 56 may be omitted.
As shown in Figure 4, the cable may be pro~ided with a loadbearing layer 58. I~ a dielectric layer 56 is provided, the loadbearing layer is preferably fabr~cated about it. The loadbearing layer serves as the primary tensile.element in the cable, although some fraction of the total load is carried by tubular member 14. This layer also acts as an abrasion-resistant layer which completely coYers and protectscable core 11. Any suitable material such as polyethylene, polyamides, polyimides, epoxies, and other similar plast.ic materials may be used for the layer 58. In a preferred embodiment, this la~er comprises a contrahelix o~ plastic filaments contained in a matrix of thermosetting epoxy. The fabrication of this layer ~ay be.done in a known manne~ by any suitable fabrication device 741 i~e.
f.~ricating an annulus utilizing a die arrangement.
The cable is generally provided ~ith an outer co~ering 60. The outer coverlng 60 serYes as a barrier to water intrusion and defocuses e~ternal cutting or abrading forces. The outer covering 60 may be formed from any suitable material such as an elastometric material. The outer covering 60 may be fabricated in any well known manner by any conventional apparatus known in the art. For example, outer coverlng 60 may be extruded in a conventional.manner by a conventional 30. extrusion apparatus 76. In a preferred embodiment, - coYering 60 comprises a layer of black polyurethane.
Figure 4 shows an embodtment of a finally assembled cable 70.
While any suitable solder ma~ be used to seal tubular conductor 14, it has been found that when a Labrication techniaue.for forming one or more of the -24- 13084~
-additional layers about cable core ll uses high temperatures, it is desirable to use a hlgh temperat~re solder such as a silver solder.
The optical flber communication cable generated by the instant inyention theoretically can have a substantially infinite length. Ca~le lengths of about 25 km. between repeaters can be fabricated by the instant method and apparatusO
The optical fiber communication cable assembled by the instant invention may have any desired di~eter;
however, the instant in~ention is particularly suited for assembling a cable having a relatively s~all diameter. The tubular member 14 may have any desired inner and outer diameters. For example, it may have an inner diameter in the range of about 0.17 cm to about 0.25 c~ and an outer diameter of about 0.24 cm to about 0.35 cm. In a preferred embodiment, where the tubular member is made from copper alloy C15100, the inner diameter of member 14 is about 0.1823 cm and the outer diameter of member 14 is about 0.2604 cm.
The overall diameter of the cable produced by the instant invention may be in the range of about 0.821 cm , . ..
to about 0.977 cm. In the preferred embodiment having a tubular member of copper alloy C15100, the overall cable diameter is about 0.9267 cm.
Strip 12 used to produce tubular member 14 may have an~ suitable con~iguration. For e~ample, strip 12 ,'7 . could have a trapezoidal shape.
Assembling ~n optical fiber communication cable in . .
accordance with the method of the instant in~ention has several adYantages. ~irst, the optIcal fiber or fibers and/or the cushioning material ~ay be inserted into the tubular member at reduced pressure thereby reducing the likelihood of breaking, kinking, or damaging the optical fiber or fibers. Second, the tubular member can be formed with an effectiYe seal providing a high degree o~ hermet.icity. Thirdg the tubular member can be formed so that it has a reIatively small diameter, thereby reducing the o~erall cable di~meter.
The cable produced by the instant invention can be used in ~oth underground, aboYeground, and undersea communication applications. For example, it could be used to supply data support and power to a deep sea sensor. It could~also be used for underground, above-ground, and undersea telephone applicationsO
While the tubular member has been described in a preferred embodiment as being formed from copper alloy Cl5100, i~ may be formed ~rom any metal or metal alloy exhibiting the desired conductivity, strength, and formability characteristicsO
While the mechanism for seal~ng the tubular -. member has been described ~n terms of a particular soldering operation, any suitable soldering, brazing or welding technique may be used. For example, the seallng operation may be performed.using a high intensity welding or laser apparatus.
. While t~e first embodiment of the capillary means for releasing..the cushioning material-and the fiber.or fibers into the tubular member has been shown as having concentric passageways with dif~erent lengths, the capillary means may be modified so that the concentric passageway-s have substantially the same length and substantially simultaneously release the cushioning material and the fiber or fibers into the ~ubular member. In.addition, the capillary means 17 may be ~odified if desired so that the passageways are non-concentric. ~urthe~more, the passageway or passageways of the Yarious capillary ~eans or protective sheath ~bodi~ents may have any desired cross-sectional shape and any desired longitudinal configuration and e~tent.
While the optical fiber communication cable is shown as haYing a dieIectr.ic layer, a loadbearing layer -26- 133~4-M3 and an outer co~ering, any number of protective layers may ~e fabric~ted about the core.
It is apparent that there has been provided with this invention a nove] ~ethod of assembling an optical fiber communication cable which fully satisfies the objects, means, and advantages set forth hereinbe~ore.
While the invention has been described in c bination with specific embod~ments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall ~ithin the spirit and broad scope of the appended claims.
This application is a divlsion of application Serial No. 416,075, filed November 22, 1982.
.. . .
METHOD AND APPARATUS ~OR ASSEMBLING AN OPTICAL
FIBER CC~IUNICATION CABLE
The invention disclosed herein relates to a method and apparatus for assembllng an optical fiber communication cable. The cable produced by the instant in~ention has utility in underground, undersea, and other communication applications.
The advent of optical fibers for use in communication applications has permitted construction of relatively small diameter cables. Generally, optical fiber communication cables are designed to provide all of the required electrical, optical, and physical functions within the smallest possible diameter. Additionally, it is desirable that the cable be constructed to have a relatively long uninterrupted length and good flexibility character-istics. ~urthermore, in undersea applications~ the cable has to withstand stresses induced by hydrostatic pressure, temperature, and sea action.
An optical fiber communication cable generally consists of several layers of appropriate plastic materials such as polyethylene, polyimide, polyamide, plastic filaments in an epoxy matrix, or other similar plastics encapsulating a strengthening layer within which a dielectric layer is used to protect ~n inner tube or cable core. This inner tube or cable core is frequently made of materials which allow it to be used as a tubular conductor. When used in undersea applications, the core often contains an appropriate polyethylene or other long chain plastic gel material to help position one or more glass optical fibers. Typical optical cable constructions are those shown and discussed in U.S. Patent Nos.
3,955,878 to Nowak, - =
~ _ . ..
.~
. ~2~ 13~4-;~
4,118g5~4 to Arnaud~ 4,146,302 to Jachimowicz, 4,201,607 to Rautenberg et al., 4,212,097 to Portinari et al., 4,239,336 to Parfree et al., 4,232~935 to Rohner et al., 4,257,675 to Nakagome et al., 4,275,294 5 to DaYidson, 4,278,835 to Jackson, 4,279,470 to Portinari et al., and 4,288,144 to Nakai et al., in German Offenlegungsschrift 2,507,649 to Tscharntke, in "Guidelines to the Design of Optical Cables'~ by Wilkins, presented at the Winter Annual Meeting, December 2-7, 10 1979 of the .4merican Society of Mechanical Engineers, in "An Electro-Optical Array Support Cable'7 by Wilkins, presented at the Winter Annual Meeting, November 16-20, 1~80 of the American Society of Mechanical Engineers, in "Recent Experience with Small, Undersea Optical Cables" by Wilkins, IEEE-EASCON, October, 1979, Washington, D.C., in ~1How Small Can an Electro-Optical Cable Be?" by Wilkins, International Telemetry Society Conference, San Diego, California, October 13-15, 1981 and in "Design and Performance of an Undersea, Single-Fiber, Multi-Repeater, Full Duplexg Electro-Optical Da~a Link", by-Wilkins et al., International Telemetry Conference, San Diego, California, October 13-15, 1981.
Various approaches for assembling these optical cables are known in the art. One approach places 25 optical ~ibers within a split aluminum tube. A copper C tube made from copper tape is then formed over the aluminum tube and fibers so as to provide a hermetic seal. Therea~ter, the copper tube ma~ be surrounded by a dielectric layer, a strength member layer, and a sheath. An alternatiYe to this approach surrounds the aluminum tube and optical fibers ~ith a copper tape layer, a dielectric layer, and a sheath. U.S. Patent No. 4, 239,336 to Parfree et al. is illustrative of these approaches.
In a second approach, a metal tube is manu~actured such as by extrusion or roll~ng o~er a metal strip.
The tube is slit open and one or more optical fibers are inserted into the t~be. If deslred, a void fillin~
gel may be inserted along with the fiber or fibers.
The tube is then squeezed shut and the slit permanently closed as by welding. The tube is finally surrounded by a dielectrlc layer, a loadbearing section, and an outer ~acket. IllustratiYe of this approach is "An Electro-Optical Array Support Cablel' by Wilkins and U.S. Patent No. ~,275,2~4 to Davidson. A similar approach is shown in U.S. Patent Nos. 4,212,097 and 4,279,470, both to Portinari et al.
Yet ano~her approach known in the art rolls an electrical conductor tube from à flat-tape stock of copper material. Prior to tube closure, the optical ( ~ 15 fiber or fibers and/or a ~oid filler or pressure buffer layer are inserted into the tube channel. The tube is then forced shut and permanently welded or soldered. Additional layers consisting of synthetic materials and containing high tensile strength materials may be used to cover the conductor tube. Illustrative of t~is type of approach are U.S. Patent Nos, 4,146,302 to Jachimowicz3 4,232,935 to Rohner et al. and 4,257,675 to Nakagome et al.
The fabrication of optical communication cables by these approaches has been hampered by an inability to ( get extremely long uninterrupted lengths of assembled cable. Furthermore, the tube has to be threaded ~ith one or more glass conductor rods or fibers whose diameter is approximately 1~2 mm. Frequently, kinking or breaking of one or more of ~he fibers occurs during threadingg resulting in non-usable cable. In addition, damage to the fibers may occur during the tube sealing operation. If. the fiber threading operation is successful, the problem of filling the tube with-the appropriate filler while maintaining the fibers in reasonable separation st~ll rem2ins.
-4- 13084-~B
It has been discoYered that when the cushioning material i9 present in the tubular conductor during the sealing operation, it sometimes flows in~o the seam being closed. This seepage of cushioning material into the seam can adversely affect the seal formed by soldering or welding. As a result, the tubular conductor does not ha~e the desired degree of hermeticity.
In accordance with the instant invention, there 10 -is provided an improYed method and apparatus for assembling an optical fiber communication cable. The method of assembly according to the instant invention comprises forming a tubular member from a strip of metal or metal alloy, sealing the tubular member, and t - 15 releasing into the sealed tubular member one or more optical fibers. By releasing the one or more optical fibers into the tubular member after the sealing operation has been completed, the likelihood of damaging the fiber or fibers is minimized.
More particularly, the method of assembly in accordance with the instant in~ention comprises pulling a strip of metal or metal alloy through a flu~ applying ! /
., ~
/
station and then through a die to ~orm a tubular member having a substant~ally square and tight seam.
After the forming operation, the tubular member is passed through a station for sealing the s~am. During the seam sealin~ operation, one or more optical fibers and~or a cushioning material are housed within a protective sheath located internally of the tubular m~er. me protective sheath substantially prevents the trans-~ission of heat from the sealing operation to the one or ~ore optical fibers and/or the cushioning material, prevents any cushioning material from adversely affecting the seam sealing operation, and in general, protects the optical fiber or fibers. After the - sealing of the se~m has been completed, the fiber or fi~ers and/or the cushioning material are released into the tubular member. In a first embodiment, the optical fiber or fibers are released into the tubular member downstream of the location where the cushioning material is released into the sealed tubular member.
In a second embodiment~ the optical fiber or fibPrs are released into the sealed tubular member simultaneousl~ with the cushioning material. ln a third embodiment, the optical fiber or fibers are released into the sealed tubular member without any ( 25 cushioning material.
If desired, the tubular member forming the core may be used as an electr~cal conductor for transmitting power. Alternativel~, the t~bular member may be used solely as a strength member.
After the core has been fabricated, it may be surrounded ~y one or more additional layers. The additional layer or layers ma~ comprise a dielectric layer, a loadbearing layer, and/or an outer covering.
The apparatus ~or assembling an optical fiber c~mmunication cable in accordance with the instant invention includes a capillary means or protective -6- 130~4-i~3 sheath for releasing the one or more optical fibers into the tubular member after the sealing operation has been completed. In a first embodiment, the capillary means comprises concentric chambers or passageways for inserting both a cushionlng material and the one or more optical fibers into the sealed tubular member. Preferabl~, one o~ the concentric chambers or passageways e~tends into the tubular member farther than the other. In a preferred embodiment, the capillar~ means inserts the one or more optical fibers ~nto the tubular member downstream of the location where the cushioning material is in~ected into the sealed tubular member. In a second embod~ment, the capillary means comprises a single ~-- 15 passageway or chamber for substantially simultaneously `-- inserting the cushioning material and the one or more optical libers into the tubular member. In a third embodiment, the capillary ~eans comprises a-single passageway or chamber for inserting one or more optical fibers into the sealed tubular member without any cushioning material.
- To substantially prevent the transmission of heat f~m the seam sea~k~ operation to the one or more fibers and~or the cushioning material, the capillary means or protective sheath is preferably formed from a material haYing a ' relatively low thermal conductivity. In addition, the capillary means or protective sheath should be formed from a material that will not be bonded to the tubular member by the means ~or sealing the seam and that can withstand the temperatures associated with the seam sealing. Suitable materials for forming the capillary means include high stainless steels, refractory alloys, ceramics and insulating materia-s. Alter-nati~ely, the capillar~ means may be formed from composite materials. The composite may comprise an -7- 13084-~B
outer material having a low thermal conducti~rit~ and an inner material havln~ a higher thermal conductivit~.
If desired, the'capillarg means ma~ be Joined to an external cooling system. By doing this, heat withln the capillary means may be readily withdra-~m.
The cable produced by the metAod and apparatus of the instant invention should ha~e a relatively small diameter and good flexibility characteristics. This cable should also be capahle of resisting sea action and of withstanding the pressures and temperatures associated with undersea applications. In addition, the ca~le produced by the method and apparatus of the instant invention is capable of being level ~ound on a storage reel, of being stored on a reel with a minimum ('; 15 total volume and of having relatively long uni~ter-rupted lengths.
It is an ob~ect of the present invention to provide a method and apparatus for assembling an optical fiber communication cable having a relatively small diameter.
-It is a further object of the present invention to provide a method and apparatus as above ~or assembling an optical fibe~ communication cable having a relatively relatively long uninterrupted length.
It is a further ob~ect o~ the present invention ( to provide a method and apparatus as above for assembling an optical ~iber communication cable ~a~ing a sealed tubular''core with a relatively high degree of hermeticity.
It is a further object of the present in~ention to provide a method and apparatus as abo~e for inserting one or more optical fibers into the tubular core after the sealing operation has been completed so that the risk of damage to the fiber or fibers are min~mized.
It is a further object o, the present invention to pro~Jide a method and apparatus as above for insertin~ a cushioning material about the fiber or fibers, if de-sired, without adversely affecting the sealing of the tubular core.
In accordance with a particular embodiment of the invention there is provided an apparatus for assembling an optical fiber communication cable.
The apparatus includes means for forming a tubular member by progressively deforming an advancing metal strip member, said means for forming having a generally downwardly facing longitudinally extending seam. The apparatus also includes a source of molten solder and a means for contacting the downwardly facing seam with the solder.
These and other objects will become more apparent from the following description and drawings.
Embodiments of the method and apparatus for assembling the optical fiber communication cable and the cable produced by the instant invention are shown in the drawings wherein like numerals depict like parts.
Figure 1 is a schematic representation in partial cross section of a side view of an apparatus used to assemble a first type of optical fiber communi-cation cable core having one or more optical fibers and a cushioning material.
Figure 2 is a schematic representation in partial cross section of a bottom view of a portion of the apparatus of Figure 1.
Figure 3 is a schematic representation in partial cross section of the apparatus used to fabri-cate the outer layers of an optical fiber communica-tion cable.
Figure 4 is a schematic representation in cross section of a first cable embodiment produced in accordance with the instant invention.
Figure 5 is a schematic representation in partial cross section of a side view of a second embodiment of an apparatus used to assemble an optical fiber communication cable core having one ,~
,, ,, ~
:~L~ 3 - 8a -or more optical fibers and a cushioning material.
Figure 6 is a schematic representation in partial cross section of an alternative embodiment of an apparatus for assembling an optical fiber communication cable core without any cushioning material.
Figure 7 is a schematic representation in cross section of an optical fiber communication cable core formed by the apparatus of Figure 6.
B~
-9- 13084-~B
In accordance with this ~n~ention, a method and apparatus for assembling an optlcal ~iber c~mmunication cable are provided. T~e instant method of assembly makes use of a tube form~ng technique to permit assembly of a cable having a core comprising a metal or metal alloy tubular me~er having a relatively small diameter and a relatively long uninterrupted length.
The cable produced by the instant method and apparatus should satisfy all electrical, physical, and operational constraints for underground, undersea, and other uses.
Furthermore, the instant method and apparatus permit production of a relatively small diameter cable ha~ing a core exhibiting excellent strength and ~lexibility characteristics~ The cable produced by the instant method and apparatus may ha~e a diameter substantially about one-quarter that of a conventional cable and a transportation Yolume substantially about one-tenth that of a conventional cable.
The method of assembling the optical fiher communication cable of the in~ant inventlon i5 relatively lnexpensi~e and simple to perform. The instant method readily solves the problem of forming, filling, and sealing a tubular member with ne~ligible risk to the fiber or fibers within the member. It also produces a tubular member that is substantially free of internal and external rough spots, both substantially circular and concentric, substantially clean on both the internal and external sur~aces before~ during, and after tube fabrication, and capable of being used as an elec~rical conductor.
Referr~ng now to Figures 1-3, an apparatus 10 is shown for assem~ling a first type of cable core ll that is particularly use~ul in undersea applications. The apparatus 10 takes a strip 12 of metal or metal alloy and forms it into a tubula~ member 14 by pulling the --10- 13084-~
strip through a forming die 16l The use of a die to form a tube from strip material is well known in the art. Manufacturing Proc-esses, Sixth Edition, by Myron L. 3egeman et al., John Wiley and Sons, Inc.-, 1957, pp. 283-285, discloses Yarlous dies for form~ng a tube out of strip ~aterial. Any suitable die arrangement may be utilized. Ho~ever, prior to passlng through die 16, strip 12 is passed through a fluxing statlon 15. Fluxing station 15 applies a flux to the edges of the strip 12. Fluxing station 15 may comprise any conventional means ~or appl~in~ any con~entional flu~ known in the art. Preferably, the tubular member 14 is formed ~ith a longitudinal seam 38 having square and tight edges 40. While the seam 38 may be formed on ~~ 15 any side, preferably seam 38 faces downwardl~. An~
sultable means such as a t~ke-up reel not shown may be used to pull strip 12 through flu-~ing station 15 and die 16.
After the tubular member 14 has been ~ormed by the die 16, it is passed to a station 42 for sealing the seam 38. .Statton 42 ma~ comprise any suitable sealing mechanism, i.e. soldering means;, welding means, brazing means, etc. known in the art. In a preferred arrangement, station 42 comprlses means for soldering the seam 38.
( A supply of solder is provided in a sump or bath 44. The solder is fed in a conventional manner, such as by a pump not shown, to a soldering head 46 having an orifice 47. The solder is preferably fed through the soldering head 46 and orifice 47 at a pressure suffic~ent to create a spout of solder. The tubul~r member 14 and the se~ 38 are passed over the spout o~ solder. The movement of the tubular member over t~e spout of solder and surface tension drive the solder into the seam interface formed by the edges 40.
The sold~r capillaries up into and substartially fills P~2~,~
~ 13084 I~
the seam 38. After the solder solidlfies; tne tu~ular member 14 is completely sealed~ B~ seallng the tubular member in this fashlon, the tubular member ~a~
be provided with a relatively high degree of hermeticity. Any suitable solder including silver solders, high-temperature solders, low-temperature solders such as lead-tin solder, lead-antimony solder, tin-antimony solder, etc., may be used to seal se~m 38 and tubular member 14.
10After passing over the soldering head 46, tubular member 14 passes over a wiping device 48 for removing any excess solder. Wiping device 48 may c~mprise a spring ~ipe or an~ o~her suitable wiping mechanism.
During the tubular member forming and sealing operations, at least one optical fiber 18 and a C~ cushioning material 30 are located within a protecti~Je sheath or capillary means 17. The tube ~orming operation preferably takes place about the protective sheath or capillary means 17. The capillary means 17 is intended to prevent damage to the at least one fiber 18 and cushioning material 30 from the sealing operation and to preYent the cushloning ma~erial from seeping into the seam and adversely affecting the sealing operation. A~ter the solder has soliaified and the tubular member 14 has been sealed, at least (one optical fiber 18 and a cushioning material 30 are inserted lnto the tubular member~ As used herein, the term inserted means released from the capillary ~eans-and deposited into the sealed tubular member.
3Q In a preferred embodiment of the instant inventlon, the cushioning material 30 is inserted into the tubular member 14 ~ust upstream of the insertion o~ at least one optical fiber 18 ~nto the tubular member The capillary ~eans or protective sheath 17 ~or insertlng the at least one optical fiber 18 and the cushioning material 30 into the tubular member 14 ~-12 130~4~
comprises a first chamber or passageway 20,through which the optical fiber'or ~ibers 18 pass and a concentric sec'ond chamber or passageway 32 for insertlng the cus~ioning materlal 30. Chamber or passageway 20 has a pressure seal 22 with an inlet opening 24 at a first end. The optical fiber or fibers 18 enter the ~assageway 20 through the opening 24. At the opposite end o~ passage~ay 20 is an outlet opening 26. Passageway 20 and outle~ 26 guide the optical fi~er or fibers 18 and deposit or release the fiber or fibers 18 into the tubular member 14 preferably after ~the solder has solidified and the tubular member has been sealed. One ad~antage to releasing the fiber or fibers 18 into the tubular ~ember after the sealing ~-- 15 operation has been completed is that the risk o~ damage `'' to the fiber or fibers as a,result of the sealing operation is minimized. In a preferred method of assembling th s type of optical fiber communication cable, the fiber or fibers 18 are inserted into the tubular member 14 downstream of the locatlon where the cushioning ma,terial 30 has been injected or inserted into the tubular member 14. Although any suitable ~echnique may-be used, fiber or fibers 18 are preferably deposited lnto tubular member 14 by pulling the fiber or fibers from one end by an~ suitable means not shown in any suitable manner.
In a preferred embodiment, the chamber or passagew-ay 32 for inserting cushioning material 30 into the't~bular me~ber concentrically surrounds the passageway 20. ~he cushloning material 30 enters the passageway 32 through an inlet opening 34, preferably whi-le under pressure. The passageway 32 has an outlet ,opening or e~it nozzle 36 through which the cushioning material 30 flows into the tubular ~ember. Passageway 32 e~tends a distance sufficient to insure that the cushioning material 30 does not ~lo~ into the tubular -13- 13~84-.~3 member until after.the solder has so~d~ied. By~,ralt ~
until after the solder has solldlfied and the tubular member 14 has been sealed to in~ect cushionlng material 30 into the tubular member 14, any risk of the cushioning material adversely affecting the sealing operation or vice-~ersa is minimlzed and an impro~ed seal may be effected. If cushioning mate~ial 30 were inserted before the sealing operation had been completed or before solder solidification, the cushioning material 30 could flow into the seam and ad~ersely affect the sealin~ operation by preventing the solder ~rom capillarying up into the seam interface.
The cushioning material 30 is preferably intro-- 15 duced into passageway 32 under pressure so that as the cushioning material 30 flows into tubular member 14, it substantially fills the tubular member 14 and substantially surrounds the optical fiber or fibers 18.
Cushioning mater~al 30 helps position the fiber or 20 fibers 18 wi.thin tubular ~ember 14. Any suitable mechanism not shown can be used to supply the cushioning material 30 under pressure to passageway 32.
The cushioning material 30 is in part caused to flow through opening 36 by the motion of tubular memoer 14 ,.- 25 and fiber or fibers 18. The mo~ement of t~bular member - 14 and fiber or f}bers 18 in the direction of arrow~A
creates a suction force on the cushioning material 30.
This suction force helps draw the cushioning material 30 through opening 36 and.into tubular member 14.
Although the cushioning material 30 may be introduced into passageway 32 in substantially any fo-rm and at substantially any desired temperature, it has-been found to be desirable to insert the cushioning material 30 into the passageway 3~ in a heated condition. This heated condition impro~es the flow-ability of the cushioning materlal 30 by making the . ~ .
-~4- 13084~
cus~ionlng material ~ore fluid. As a result of th~s lmpr~ved flo~ability, it is belieYed that the cushioning material can be drawn out of the nozzle 36 and into the tubular member at a lower suction force than that ordinar~ly required. Any suitable conventional heating device not shown ma~ be used to heat the cushioning material 30 either before or after it enters the passage~a~ 32.
In a preferred embod~ment of the capillary means 17, passagewa~s 20 and 32 are not coextensive.
Preferably, the outlets 26 and 36 are arranged so that the cushioning materlal 30 enters the tubul~ member 14 upstream of the location where the release of the optical fiber or fibers 18 into the tubular member (- 15 takes place.
If necessary, tubular member 14 may be passed through a die 50 for sizing the tubular member 14 to its exact desired dimension. Sizing die 50 preferably ~ comprises a sinking die. If a sizing die is utilized, the optical fiber or fibers 18 are preferahly inserted ~nto the tubular member just prior to or simultaneous with the tubular member 14 passing through the sizing die 50.
By inserting the cushioning material 30 and the f~ber or fibers 18 in the manner previously described, ~- it is believed that the magnitude of the forces required to lnsert t~e cushioning material 30 and the flber or flbers 18 into tubular member 14 may be reduced. ~y reducing these forces, the likelihood of damag~ng or klnking the optical fiber or fibers 18 during lnsertion is minimized.
In Figure 5, an alternative embodiment of an apparatus 80-for assembling the cable core 11 is shown.
As tn the embodment of Figures 1-3, a strip 12 of metal or ~etal alloy is pulled through a fluxing station 15 for applying a flux to the strip edges 40 --15- 1~084~
and then throu~h a die ].6 for ~ormlng the tubular member 14. The tubular member 14 is then passed o~r a station 42 for seallng the seam 38.
A~ter the tubular member has been sealed and the sealing material, i.e. solder, has solidified, the cushioning material 30 and the fiber or fibers 18 are inserted substantially si~ultaneously b~ the capill2r~
means or protective sheath 81. The capillary means 81 preferably comprises a single passageway 86 having a pressure seal-82 with an inlet opening 84 at a first end. The optical fiber or fibers 18 enter the passageway 86 through the opening 84. On a sidewall of the passageway 86, preferably adjacent the seal 82, an inlet opening 87 is pro~ided for supplying cushioning material 30 into the passageway 86. In a preferred arrangement, the pressure seal 82 and the inlet opening 87 are at a substantially right angle to each other. At the end of the passageway 86 opposed from pressure seal 82, an outlet opening 88 is proYided.
The passageway 86 extends a sufficient distance into the tubular member that the fiber or fibers 18 and the cush~oning material 30 are released into the tubular member 14 after the solder has solidified and the t1lbular member 14 has been completely sealed. As before, by waiting until after the solder has solidified and the tubular member 14 has been completely sealed to release the cushioning material 30 into the tubular member 14, any risk of damaging the cushioning material 30 or ad~ersely affecting the sealing operation by cushioning material 30 seeping into the seam 38 is minimized.
Wh~le any suitable technique may be used~ fiber or - fibers 18 are preferably deposited into tubular m~mber 14 by pulling the fiber or fibers 18 from one end by any suitable means no~ shown in any suitable manner.
~3 -16- 13084~
The cushion~ng material 30 is preferably inserted lnto passageway 86 while under pressure so that it substantially fllls the tubular member 14 and substantially surrounds the optical fiber or fibers 18.
The cushioning material 30 is also pre~erably inserted into passageway 86 in a heated condition so that ~he flo~ability of the cus-hioning material 30 is impro~ed.
It is desirable that the flowability of the cushioning material 30 be improved because while the fiber or fibers 18 mo~e at substantially the sane speed as the tubular member 14, the cushioning ~aterial 30 needs to flow at a greater speed since ~t has to fill the tubular member. It is also believed that this increased flowability also reduces the magnitude of the force needed to be exerted on the cushioning C mater~al to get it to flow into tubular member 14.
The cushioning material 30 is in part caused to flow - through the opening 86 by a suction force created by - the motion o~ tubular member 14 and fiber or fibers 18.
If a sizing die 50 need be used, outlet opening 88 is preferably located substantially near the location of the sizing die. Again, sizing die 50 preferably comprises a sinking die. By positioning the outlet opening 88 at this locationg it is believed that the magnitude cf the forces required to insert the ,- cushioning material 30 and the fiber or fibers 18 into tubular member 14 may be reduced.
For certain applications, it is not necessary to ha~e a cushioning material surround the optical fiber or fibers ~ithin the cable core. Figure 6 shows an alternative appara~us 100 for ~orming such a cable core 11'. The apparatus 100 is readily adaptable for inserting one or more optical fibers in an unconstrained condition into a closely surrounding tubular member.
-17- 130~4~
As ln the previous ~mbodiments, a strip 12 o~ the metal or metal alloy is pulled through a fluxi~g station 15 ~or applying a ~lu~ to the strip edges 40 and then through a die 16 for forming the tubular member 14. The tubular member 14 is then passed o~Jer a station 42 for sealing the sea~ 38.
After the tubular member has been sealed and the sealing material, i.e. solder, has solidified, the fi`oer or fibers 13 are inserted or released ~nto the tubular member by capillary means or protective sheath 102. The caplllary means 102 comprises a single passageway 108 having a seal 104 with an inlet opening 106 at a first end. The optical ~iber or fibers 18 enter the passageway 108 through the opening 106. At the end of the passageway 108 opposed to the seal 104 is outlet opening 110. The passageway 108 extends a -sufficient distance into the tubular ~ember that as the fiber or fibers 18 emerge from the opening 110, the fiber or fibers are released into the member 14 after t~e solder has solidified and the tubular member 14 has been com~letely sealed. The capillary means or protective sheath 102 minimizes the possibility of the sealing operation damaging the optical fiber or fibers.
While any suitable technique may be utilized, the fiber or fibers 18 are preferably deposited into tubular member 14 by pulling the fiber or fibers 18 from one end ~y any suitable means not shown in any suitable ~anner. If needed, apparatus 100 may be proYided with a sizing die not shown for providing 30. cable core 11~ with a.particular outer dimension.
It is desirable that the capillary means or protectiYe sheath 17, 81, and 102.be made from a - material having certain properties. First, the material should not be bondable to the metal or metal alloy forming member 14. If the material were bondabIe, the sealing operation could bond the 18- 13~84-~13 capillary means to the member 14. Second, the material should be able to withstand the temperatures associated wlth the sealing operation and, therefore, should have good high tem~erature properties. Finally, the material should have high strength characteristics and - should have a relatively low thermal conductivity. B~J
providing a material having a relatively low thermal conductivity~ tle or substantially none of the heat-created-during the sealing operation will be transmitted to the optical fi~er or fibers and/or any filler material. Suitable materials out of which the capillary means or protective-sheath may be ~abricated include refractory alloys such as high-nickel alloys, ceramic materials, high stainless steels, sapphire, insulating ~ype materials and composites comprising an ( - outer material having a relatively low thermal conductlvity and an inner material having a higher thermal conductivity than the outer material. It should be recognized that the aforementioned materials are exemplary and should not be limi~ing in an~ way.
O~her suitab~e materials ~ay be used.
In certain high temperature situations, it may be desirable to provide the capillary means or protective sheath with a cooling arrangement. In this way, each optical fiber and/or any cushioning material may be additionally protected from heat generated dur~ng the sealing operation. Cooling could be provided in any suitable con~entional manner. For example, the capillary means or protectiYe sheath could be connected to an external cooling apparatus 112. Cooling apparatus 112 may c~mprise any suitable conventional cooling apparatus known in the art. Cooling could be pro~ided to any or each passage~ay of the capillary means or protecti~e sheath. In situations where it is desirable to provide cooling, it ~ould be advantageous to form-the capillary means or protective sheath out of -]9- 13084-i~B
a composite material as discussed aboYe. The higher thermally conductive inner material could be connected to the cooling apparatus while the outer material performs its protective functionO
The cable core 11 or 11' may conta:in any desired number of optical fibers 18. In a preferred embodiment, one to six optical fibers are located within the cable core. Preferably, each optical fiber 18 comprises a photo-conductor glass rod; ho~ever, any suitable optical fiber may be used in the cable.
While any suitable technique may be used to deposit the fiber or fibers into the tubular ~ember 14, it is preferred to deposit the fiber or fibers by pulling from one end without applying any significant back tension. Since each fiber 1~ remains substan-tially unconstrained during the tubular member forming - operation, each fiber is under substantially zero tension at the same time that the tubular member 14, as a result of the core ~ormation process, is near maximum elastic tension. By doing this, it is possible to put each fiber in static compression after unloading so that an increment of plastic strain in the sheathing equal to the net static compression could be imposed without kinking the fiber or f~bers 18.
~lternati~ely, if desireda the optical fiber or fibers 18 may be helically wound within the cable core 11 or 11 r, Cushioning material 30 may comprise any suitable non-setting vo~d filler. The temperature to which the cushioning material is heated depends upon the selected filler and its ~iscosity characteristics. In a preferred embodlment, cushioning material 30 comprises a gel which is initially introduced into its passageway at a temperature in the range of about 35C to about 150C, preferably at about 100C.
3~
The use of cushioning material 30 is highly desirable in a cable which may be subjected to high bending or hydrostatic stresses. Cushioning material 30 has two primary functions. First, it lubricates the fiber or fibers 18 to prevent stiction and micro-bending. Second, it provides the fiber or fibers 18 with a hydrostatic, ambient pressure environment.
Strip 12 which is used to form tubular member 14 preferably has an initial width greater than the outside circumference of the tube formed by forming die arrangement 16. The initial width is about 5% to about 15%, preferably about 10%, greater than the tube outside circumference. By starting with such an initial strip, the seam 38 created dur-ing tube forming will be put into significant com-pression, thereby remaining substantially closed even if spring back occurs. If it is desired to form a mechanical interlock joint, the edges 40 of strip 12 may be shaped in any suitable manner so that a mech-anical seal is formed along seam 38 during tubeforming. -By using a strip 12 having such an initialwidth and pulling the strip through a forming die 16, the formed tube will be a drawn tube having a gener-ally longitudinally extending seam 38 defined byopposing substantially non-linear deformed edges whose length from the outside of said tube to the inside of said tube exceeds the thickness of the strip. These deformed edges are the inherent result of Applicants' forming technique. It should also be noted that the transverse cross-sectional area of the initial strip exceeds the transverse cross-sectional area of the formed strip tube.
- 20a -The extra volume of metal also inherently assists in the formation of a tube 14 having a rela-tively tight seam 38 without a notch or well at the outer periphery of the seam. Further, the edges defin-ing the seam 38 are inherently deformed by the tube forming technique described above to provide substan-tially non-linear and intermeshing edges not shown.
This results in an increase in surface area of the seam edges to which the sealing material can adhere as compared to the original strip 12 edges thereby improving the resultant strength of the seal. This - also results in better hermeticity than prior cable core assemblies.
The deformed intermeshing edges are the in-herent result of the processing in accordance with the above-described techniques and do not correspond to the shape of the original strip edges. The de-formed edges result from the drawing of the tube by the process of this invention.
In contrast, a tube formed by folding even with the use of a die forming technique would not have such deformed edges since in a folding operation the starting strip would not include the excess--material which the process of this invention uses to form the :
deformed edges. A deficiency of the folding technique is that a well or depression occurs at the outer sur-face along the seam. In accordance with this inven-tion, the presence of excess material from the metal i; strip causes the outer surface to form against the - 30 die so as to eliminate such well or depression along the seam. This is highly significant since it reduces the amount of solder or brazing material which would be required to provide a circular outer periphery to the resultant tube 14.
Z~
- 20b -The material comprising strip 12 and tubular member 14 should possess certain conductivity, strength, and thickness-to-diameter ratio characteristics. The material should possess a high electrical conductivity since member 14 preferably acts as a conductor in the final cable. In the cable system, tubular member 14 may be used to carry current between repeaters not shown which may be spaced about 25 km. apart.
Since member 14 is preferably the only metal component in the cable, the material should possess high strength properties. The material preferably possesses significant yield strength and a relatively high yield strain. The member should be formed from a material that has a yieId strength sufficient to keep the tubular member in a substantially elastic state for any degree of cable bendin~. By havlng a member that is maintained in a substantially elastic state and substantially never in a plastic state, the risk of breaking the glass fiber or ~ibers due to placing the glass fiber or fibers in tension is minimized.
A material having a relatively high yield strain is important since it reduces the overall cable diameter. The yield strain of the material forming the tubular member also dete~mines how much of the ultimate strength of an outer loadaearing layer can be used without permanently straining the tubular mem~er and breaking the optical fiber or fibers.
T~e material used to produce tubular member 14 should also be capable of sustaining certain coiling forces during fabrication and installation. Therefore, a thickness~-to-diameter ratio K which indicates good formabil~ty characteristics is required. If the material does not possess good formability character-istics, the tubular member ~all ma~ be crinkled or buckled during tube formation. I~ this occurs on the inner surface of the member, optical fiber or fibers 18 may suffer microbending against angular surfaces and large inc~eases in atten~ation may result.
A preferred strip material has a conductivity in the range of about 25 to 102~o IACS, a yield strength in the range of about 30 to about 90 ksi, preferably in the range of about 50 ksi to about 60 ksi, a yield strain in the range o~ about 0.0017 to 0.0095 and a thickness-to-diameter ratio of about 0~ 02 to 0.50. .
number of metals and alloys possess the required combination of strength, conductivity, and thickness-to-diameter ratio and may, there~ore, be utilized. -In a preferred embodiment, the material forming strip 12 and tubular member 14 comprises a copper/zirconium alloy, -22- 13084-;~
de~ignated CDA 15100, manufactured by Olin Corporation.
Copper alloy C15100 has a conductiYity o~ about 95~
IACS, a yield strength of about ~2 ksi, a yield strain OL about 0~0034 and a thickness-to-diameter ratio of about 0.15.
Since the strip is being pulled through a fluxing station, a forming die and/or a sizing die, a slightly harder material is desirable in order to avoid strip breakage. The material selected should haYe a hardness of at least about 1/4 hard. Copper alloy C15100 can be hardened to meet this requirement. In a preferred embodiment, copper alloy C15100 has a hardness in the range of about at least 1/4 hard to about spring. It has been found that a tubular member formed from copper alloy C15100 in this hardness range is particularly suitable for situations where an outer layer or layers is to be ~abricated about the cable core using high temperature fabrication techniques.
After cable core 11 or 11' has been assembled utilizing either apparatus 10, apparatus 80, or apparatus lOOj the cable core may be surrounded by one or more additional laye~. For examDle, dielectric layer 56 may ~e fabricated about the member 14. A typical cable will ha~e such a dielectric layer if the tubular member 14 is to be used as an electrical conductor.
Dielectric layer 56 may be fabricated in any suitable conventional manner using any suitable conventional apparatus. ~or e~ample, dielectric layer 56 may be extruded about the cable core by any suitable extruding arrangement 72 in a conventional manner. ~he dielectric layer 56 preferably comprises a high density polyethylene, although any suitable ~aterial -may be used. The dielectric layer preferably takes no part in system telemetry and acts only as an insulator.
However, ~f desired, it ma~ be designed to take part in the system telem2try. ~ tubular member 1~ is not -23- 130~4-~
used as an electrical conductor, the d~electric la~;er 56 may be omitted.
As shown in Figure 4, the cable may be pro~ided with a loadbearing layer 58. I~ a dielectric layer 56 is provided, the loadbearing layer is preferably fabr~cated about it. The loadbearing layer serves as the primary tensile.element in the cable, although some fraction of the total load is carried by tubular member 14. This layer also acts as an abrasion-resistant layer which completely coYers and protectscable core 11. Any suitable material such as polyethylene, polyamides, polyimides, epoxies, and other similar plast.ic materials may be used for the layer 58. In a preferred embodiment, this la~er comprises a contrahelix o~ plastic filaments contained in a matrix of thermosetting epoxy. The fabrication of this layer ~ay be.done in a known manne~ by any suitable fabrication device 741 i~e.
f.~ricating an annulus utilizing a die arrangement.
The cable is generally provided ~ith an outer co~ering 60. The outer coverlng 60 serYes as a barrier to water intrusion and defocuses e~ternal cutting or abrading forces. The outer covering 60 may be formed from any suitable material such as an elastometric material. The outer covering 60 may be fabricated in any well known manner by any conventional apparatus known in the art. For example, outer coverlng 60 may be extruded in a conventional.manner by a conventional 30. extrusion apparatus 76. In a preferred embodiment, - coYering 60 comprises a layer of black polyurethane.
Figure 4 shows an embodtment of a finally assembled cable 70.
While any suitable solder ma~ be used to seal tubular conductor 14, it has been found that when a Labrication techniaue.for forming one or more of the -24- 13084~
-additional layers about cable core ll uses high temperatures, it is desirable to use a hlgh temperat~re solder such as a silver solder.
The optical flber communication cable generated by the instant inyention theoretically can have a substantially infinite length. Ca~le lengths of about 25 km. between repeaters can be fabricated by the instant method and apparatusO
The optical fiber communication cable assembled by the instant invention may have any desired di~eter;
however, the instant in~ention is particularly suited for assembling a cable having a relatively s~all diameter. The tubular member 14 may have any desired inner and outer diameters. For example, it may have an inner diameter in the range of about 0.17 cm to about 0.25 c~ and an outer diameter of about 0.24 cm to about 0.35 cm. In a preferred embodiment, where the tubular member is made from copper alloy C15100, the inner diameter of member 14 is about 0.1823 cm and the outer diameter of member 14 is about 0.2604 cm.
The overall diameter of the cable produced by the instant invention may be in the range of about 0.821 cm , . ..
to about 0.977 cm. In the preferred embodiment having a tubular member of copper alloy C15100, the overall cable diameter is about 0.9267 cm.
Strip 12 used to produce tubular member 14 may have an~ suitable con~iguration. For e~ample, strip 12 ,'7 . could have a trapezoidal shape.
Assembling ~n optical fiber communication cable in . .
accordance with the method of the instant in~ention has several adYantages. ~irst, the optIcal fiber or fibers and/or the cushioning material ~ay be inserted into the tubular member at reduced pressure thereby reducing the likelihood of breaking, kinking, or damaging the optical fiber or fibers. Second, the tubular member can be formed with an effectiYe seal providing a high degree o~ hermet.icity. Thirdg the tubular member can be formed so that it has a reIatively small diameter, thereby reducing the o~erall cable di~meter.
The cable produced by the instant invention can be used in ~oth underground, aboYeground, and undersea communication applications. For example, it could be used to supply data support and power to a deep sea sensor. It could~also be used for underground, above-ground, and undersea telephone applicationsO
While the tubular member has been described in a preferred embodiment as being formed from copper alloy Cl5100, i~ may be formed ~rom any metal or metal alloy exhibiting the desired conductivity, strength, and formability characteristicsO
While the mechanism for seal~ng the tubular -. member has been described ~n terms of a particular soldering operation, any suitable soldering, brazing or welding technique may be used. For example, the seallng operation may be performed.using a high intensity welding or laser apparatus.
. While t~e first embodiment of the capillary means for releasing..the cushioning material-and the fiber.or fibers into the tubular member has been shown as having concentric passageways with dif~erent lengths, the capillary means may be modified so that the concentric passageway-s have substantially the same length and substantially simultaneously release the cushioning material and the fiber or fibers into the ~ubular member. In.addition, the capillary means 17 may be ~odified if desired so that the passageways are non-concentric. ~urthe~more, the passageway or passageways of the Yarious capillary ~eans or protective sheath ~bodi~ents may have any desired cross-sectional shape and any desired longitudinal configuration and e~tent.
While the optical fiber communication cable is shown as haYing a dieIectr.ic layer, a loadbearing layer -26- 133~4-M3 and an outer co~ering, any number of protective layers may ~e fabric~ted about the core.
It is apparent that there has been provided with this invention a nove] ~ethod of assembling an optical fiber communication cable which fully satisfies the objects, means, and advantages set forth hereinbe~ore.
While the invention has been described in c bination with specific embod~ments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall ~ithin the spirit and broad scope of the appended claims.
This application is a divlsion of application Serial No. 416,075, filed November 22, 1982.
.. . .
Claims (5)
1. An apparatus for assembling an optical fiber communication cable, said apparatus comprising:
means for forming a tubular member by progress-ively deforming an advancing metal strip member, said deformed metal strip having a generally downwardly facing, longitudinally extending seam;
a source of molten solder; and means for contacting said downwardly facing seam with said solder.
means for forming a tubular member by progress-ively deforming an advancing metal strip member, said deformed metal strip having a generally downwardly facing, longitudinally extending seam;
a source of molten solder; and means for contacting said downwardly facing seam with said solder.
2. The apparatus according to claim 1 further comprising:
said tubular member forming means comprising a die for forming said tubular member from a strip of high strength copper alloy having a desired transverse strip cross-sectional area which exceeds a transverse cross-sectional area of said tubular member to be formed from said strip;
means for drawing said strip through said die; and means for inserting at least one optical fiber into said tubular member, whereby said seam is defined by a pair of opposed substantially non-linear deformed edges whose length from the outside of said tubular member to the inside of said tubular member exceeds the thickness of said strip.
said tubular member forming means comprising a die for forming said tubular member from a strip of high strength copper alloy having a desired transverse strip cross-sectional area which exceeds a transverse cross-sectional area of said tubular member to be formed from said strip;
means for drawing said strip through said die; and means for inserting at least one optical fiber into said tubular member, whereby said seam is defined by a pair of opposed substantially non-linear deformed edges whose length from the outside of said tubular member to the inside of said tubular member exceeds the thickness of said strip.
3. The apparatus according to claim 2 further comprising:
said fiber inserting means further including means for injecting a cushioning material into said tubular member, said cushioning material substantially surrounding and positioning each said optical fiber.
said fiber inserting means further including means for injecting a cushioning material into said tubular member, said cushioning material substantially surrounding and positioning each said optical fiber.
4. The apparatus according to claim 2 further comprising:
said fiber inserting means being fabricated from a material which is unbondable to said tubular member and has a relatively low thermal conductivity, said fiber inserting means having at least one passage-way through which said at least one optical fiber passes, whereby heat created during said seam solder-ing does not adversely affect said at least one optical fiber.
said fiber inserting means being fabricated from a material which is unbondable to said tubular member and has a relatively low thermal conductivity, said fiber inserting means having at least one passage-way through which said at least one optical fiber passes, whereby heat created during said seam solder-ing does not adversely affect said at least one optical fiber.
5. The apparatus according to claim 1 further comprising:
said contacting means comprising a solder head having an aperture through which said solder flows and means for applying pressure to said solder to create movement of said solder through said aper-ture, whereby a spout of solder is formed and movement of said tubular member and said downwardly facing seam over said spout of solder causes said solder to capillary up into and substantially fill said seam and to provide said tubular member with a desired degree of hermiticity.
said contacting means comprising a solder head having an aperture through which said solder flows and means for applying pressure to said solder to create movement of said solder through said aper-ture, whereby a spout of solder is formed and movement of said tubular member and said downwardly facing seam over said spout of solder causes said solder to capillary up into and substantially fill said seam and to provide said tubular member with a desired degree of hermiticity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000477200A CA1212828A (en) | 1981-11-23 | 1985-03-21 | Method and apparatus for assembling an optical fiber communication cable |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US32424281A | 1981-11-23 | 1981-11-23 | |
| US324,242 | 1981-11-23 | ||
| US413,846 | 1982-09-01 | ||
| US06/413,846 US4508423A (en) | 1981-11-23 | 1982-09-01 | Method and apparatus for assembling an optical fiber communication cable |
| CA 416075 CA1212828C (en) | 1981-11-23 | 1982-11-22 | Method and apparatus for assembling an optical fiber communication cable |
| CA000477200A CA1212828A (en) | 1981-11-23 | 1985-03-21 | Method and apparatus for assembling an optical fiber communication cable |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477200A Division CA1212828A (en) | 1981-11-23 | 1985-03-21 | Method and apparatus for assembling an optical fiber communication cable |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477200A Division CA1212828A (en) | 1981-11-23 | 1985-03-21 | Method and apparatus for assembling an optical fiber communication cable |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1212828A true CA1212828A (en) | 1986-10-21 |
Family
ID=27167306
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000477200A Expired CA1212828A (en) | 1981-11-23 | 1985-03-21 | Method and apparatus for assembling an optical fiber communication cable |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1212828A (en) |
-
1985
- 1985-03-21 CA CA000477200A patent/CA1212828A/en not_active Expired
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