Note: Descriptions are shown in the official language in which they were submitted.
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, - =
~ _ . ..
.~
. ~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.
-3- 13084-M3
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
! /
., ~
/
-5- 13084
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~
-- 20 -
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
-21- 13084-M3
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
-25 13084--1B
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.
.. . .
