Note: Descriptions are shown in the official language in which they were submitted.
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A METHOD OF SPLICING FIBER OPTIC CABLE
CROSS~REFERENCE TO RELATED APPLICATlONS
The present application is related to co-pending
patent application nu~ber 509,001, entitled "A FIBER OPTIC
5 CABLE SPLICING ARRANG~MENT", having the same inventive entity
and baing assigned to the same assignee.
BACKGROUND OF THE INVENTION
This invention relates in general to a method for
connecting fi~er optic cable and more particularly to an improved
method for connecting the ends of t~o single mode fiber optic
cables in order to provide for a low loss connection.
When the ends of two optical fibers are to be spliced,
the first consideration is to make the connectlon in such a manner
that excessive losses of the llght energy will not take place at
the splice.
One method presently known for making such a splice is
the use of a special machine which prepares the ends of the fibers
and also supplies an arc which heats the prepared ends. The flber
ends are then butted together under pressure, bonding the ends
together molecularly. A strengthening sleeve is then applied to
covPr the spllce. This method finds dlsadvantage ln thslt the
fiber ends must be perfectly flat and parallel and bo~h ~lbers
mu~3t be coalposed of the same typQ of fiber.
~nother method Eor eEfectlng a spllcP of two optlcal
flbers is pressure bonding. This method requires the careful
cleaving of each fiber so as to produce ends which are perfectly
flat and parallel. The ends are then butted together and a metal
jacket applied over each fiber end. This method finds
disadvantage in that the preparation of the fiber ends must match
exactly or excessive losses will o~cur. ~urther, any strain
applied to the splice may separate the fibers causing a failure of
the splice.
Stlll another method of splicing optical fibers uses an
"optical adhesive" to bond the ends of the fibers after they have
been prepared to present flat and parallel end surfaces to one
another. A metal jacket ls then used to cover the splice in order
to give strength to the joint.
In all the above referenced techniques each end of the
connecting fibers must be formed perfectly flat and parallel to
the other in order to efficient1y transmit all the light energy
with a minimum signal loss. Additionally, the two fiber optic
ends must be positione~ precisely along the hori~ontal axis or
coupling losses will result. Given the fact that the core of a
fiber optic cable may measure 10 micrometers or less the job of
cleaving and grinding the ends to form the proper surfaces for
splicing and subsequently aligning the two ends is therefor a very
exacting and labor intensive task.
One method presently known for splicing optical fiber
cable circumventing the disadvantages discussed above is the use
of optical fiber connector units. These high precision components
are comprised of a plug ferrule, receptacles and a plug polisher.
The connector units resemble those used for coaxial cable and
provide connection losses of only 0.5dB.
The disadvantage with this type of connection is the
hlgh per unit cost for these devices. For example, single mode
optical fiber connectors manufactured by Seico Instrument~ cost
upward of ~400.00 per connector.
Stlll ano~her dlsadvantage to optlcal connectors ls
~hat they muflt be assembled using epoxy ndhesives to holcl the
opt-lc~l E:Lber Ln alignment; the epoxiea often requlre exposure to
an ultrav-Lolet curing lLght or hlgh temperatures. F~lrthermore if,
once the epoxy has cured, the fiber alignment is unsatlsfactory,
the connector has to be cut off and discarded.
Accordingly~ it is the object of the present invention
to provide an improved, efficient and cost effective method for
connecting or splicing single mode fiber optlc cable.
SUMMARY OF THE INVENTION
In accomplishing the object of the present invention
there is provided a method for splicing a first fiber optic cable
to a second fiber optic cable. The first fiber optic cable
includes one end connected to a source of light energy.
~2~
The method compr:Lses prepar:Lng an end of the flrst
fiber optic cable by removing the claddlng and exposing the fiber
optic core, cleaving the exposed core and forming an optlcal
surface perpendicular to the length of the fiber optic cable and
polishing the formed optic surface into an optical finish. The
prepared end is then installed into a fixed connector stage.
An end of the second fiber optic cable is prepared in
the same manner as the first fiber optlc cable and is installed
into a movable connector stage.
The movable connector stage is then located in close
proximity to t~e fixed connector stage with the prepared end of
the first fiber optic cable coarsely located along a common
horizontal axi~ with the prepared end of the second fiber optic
cableO
An alignment device is then instaLled to the movable
connector stage and a second end of the second fiber optic cable
installed into a photo-detector device. The alignment device and
the photo-detector device are electrically connected to a control
device whereby~ responsive to the photo-detector reading the light
energy leaving the first fiber optic cable and entering the second
fiber optic cable the control device sends cGntrol signals to the
ali~nment device. The alignment device then moves the movable
connector stage relative to the flxed connector ~tage. The
~ovable connec~.or st~ge is Illoved until the photo-de~ector detect:s
n polnt of Low :Lo99 couplLng between the fLrst and second fiber
optic cables.
Once alignment is accomplished the alLgnment device and
photo-detector are removed and the movable connector stage fixed
in position relative to the fixed connector stage.
A BRIEF DESCRIPTION OF THE DUAWINGS
Fig. 1 is a block diagram illustrating the concept of
the present invention.
Fig. 2 is a top plan view of the fixed connector stage
and movable connector stage in accordance with the invention and
including an embodiment of an alignment platform for effecting the
connection of the stages.
~Lqf~ c~
Flg. 3 ls a sectlonal vlew taken substantlally alvng
line A-A of Fl~,. 2.
Fig. 4 is a sectional vlew taken substantlally along
line B-B of Flg. 2.
D~SCRIPTION OF T~1~ PREFERRED EMBODIMENT
Turnlng now to Fig. 1 of the included drawings there is
illustrated in block diagr2m the concept of the present invention.
The invention comprises a fixed connector stage 10, and a movable
connector stage 20. A fiber optic cable 11 connects the fixed
connector stage 10 to a light source 15. Light source 15, may be
any type of device presently kno~m to those skilled in the art for
injecting light into the transmit end of a fiber optic cable
system. The movable connector stage 20, is connected via fiber
optic cable 21 to a photo detector device 30. The length of fiber
optic cable 21 is variable and ideally would be a spool of the
fiber cable which will eventually be run to a receiving end in the
fiber optic cable system. The photo detector device 30 has an
electrical connectlon to a control devlce 40 with the control
device electrically connected to a flrst A direction servo driver
41 and a second B dlrection servo driver 42.
The device of the present lnvention is used to
advantage by connecting fiber optic cable 11 into the Eixed
connector stage 10 and connectlng one end of fiber optlc cable 21
into the movable connector stage 20. The opposite end oE fiber
optlc cclble 21 1EJ connected to photo-detector devlce 30. The
Plxed l0 and Inovable 2() c~onnector stages are butted together and
the 11.ght E30urce 15 turned on. Control clevice 40 ls then
activated ~llch provides control signals to servo drivers 41 and
42 operating mechanical servos that move the movable connector
stage 20 in flrst or alternatively a second directlon. The
movable connector stage is moved untll photo detector 30 detects a
peak llght output at which time a slgnal ~s sent to the control
device indicatlng allgnment of the two fiber ends has been made.
The servos are then shut down and the movable connector stage 20
tlghtened or permanently afflxed to the fixed connector stage 10.
Turlling now to Figs. 2, 3 and ~, an embodiment
depicting a way in which the concepts discussed above can be used
to advantage is illustrated. The fixed connector stage 10 is
comprised of a first fiber connector including a body 111 and a
head end 112. The connector body 111 rests on a fi~t~lre 113
partially within a longitudinal channel 114. The connector body
111 is normally permanently affixed to fixture 113. The movable
connector stage 20 is comprised of a second fiber connector
includlng a body 211 and a head end 21Z. The connector body 211
rests on a fixture 213 partially within a longitudinal channel
214.
The connector bodies 111, 112 and head ends 112, 212
are composed of a rigid metallic material while the fixtures may
be composed of a rigid plastic material. The fiber optic cable 11
extending from light source 15 would normally have its cladding
striped off the end cleaved and polished and in~erted into
connector body 111. Likewise, fiber optic cable 21 would be
prepared and inserted into connector body 211 after he same type
of preparation.
As can be seen at the sectional elevation of Fig. 2 the
fiber cable 21 enters body 211 at an end opposite the head end
212. ~efore entering the heacl end the cable passes through a
resilient ferrule 214 which ho],ds the cable ln posltion w:Lthin the
connector, as well a9~ Lsolatlng the connection cham'ber 215 from
body 212. Optlca:L Eiber 11 traver~3es and ls Lnstalled wl~hln the
flrst fl.ber connector :Ln the same manner described above for the
~econd fiber connector.
The prepared ends are then positioned adjacent the
outer edge toward the other connector head end and the connection
chamber 215 filled with matching fluid. When head ends 112 and
212 are butted against each other the prepared ends of fiber optic
cables 11, 21 are positioned in close proximity to each other but
do not contact each other. The fixed connector stage 10 is then
tighten down to a mounting surface.
In order to exactly align the two fiber ends a servo
driven platform 50 is attached to the movable connector stage 20.
A pair of holes or-lented parallel to each other traverse
internally through fixture 213. A pair of mounting pins 216
e~tending from a top plate 51 of platform 50 are arranged to be
accepted by the respective holes on flxture 213. Thereby,
mounting the movable connector stage 20 to platform 50.
Platform 50 further includes first and second servos 70
and 60 respectively mounted to the platform~ Servos 70, 60
receive control signals via lines 72 and 62 from the A direction
servo/driver 41 and the B direction servo/driver 42 respectively.
~haft 71 of servo 70 is attached to fixture 213 of movable
connector stage 20 and upon the reception of control signals from
driver 41 moves the fixture 213 in direction a-a in respect to the
fixed connector stage 10.
Shaft 61 of servo 60 is configured as a worm gear which
mates with an associated threaded shaft 53 extending from platform
51. Threaded shaft 53 is mounted within a threaded bore 54 which
extends though platform 51. Further, shaft 53 is rotatably
affixed to a base platform 55. A plurality of guide shafts 52
also e~tend from the base platform 55 through respective bores on
platform 51~
Upon the application of control signal6 ~o servo 60
from servo driver 42, shaft 61 rotates which drives shaEt 53.
shaft 53 Kotates ~ hreaded bore 54 p:latform 51 r:Ldes nlong
~uides 52. DependLag on the direction oE the rotatLon oE shaft
61, platform 51 18 either raised or lowered with respect to base
55. This action moves the movable connector stage in direction
b-b.
When the best alignment possible has been achleved the
movable connector stage is tightened down and bonded for permanent
use and movable platform 50 removed.
Although the preferred embodiment of the invention has
been illustrated, and that form described in detail, it will be
readily apparent to those skilled in the art that various
modificat:Lons may be made therein wltho~t departing from the
spirit of the invention or from the scope of the appended claims.
