Note: Descriptions are shown in the official language in which they were submitted.
lo
The invention relates to apparatus for fusion-splicing
optical fibers, and especially to a mirror mechanism therefore
The invention is especially concerned with such
apparatus which comprises two supports, for example Vie grooves, to
which the fibers are clamped so that they are aligned end-to-end.
One of the supports is movable transversely of the longitudinal axis
of the fibers to facilitate accurate alignment of the fibers.
Electrodes are arranged to provide a spark discharge in a zone
encompassing the juxtaposed ends of the two fibers. The spark
discharge heats the end portions of the fibers until they are soft
enough to fuse, whereupon they are urged together longitudinally to
cause them to fuse together.
During the alignment procedure, it is desirable to view
the fibers from more than one direction, preferably mutually
perpendicular, to ensure correct alignment in all planes through the
longitudinal axis. In known apparatus, the desired views in two
mutually perpendicular directions are provided by a Vie mirror
positioned behind the fibers with its apex parallel to the
longitudinal axis. The surfaces of the mirror are so inclined as to
reflect views from both sides of the fibers towards the viewer, for
example parallel to the optical axis of the microscope, where
applicable. To ensure that the mirror is not spattered during the
heating step, it is repositioned to one side of the optical or
viewing axis after the alignment has been effected.
I,
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31 2~3~
A disadvantage of this apparatus is that one of the
fibers is unsupported for the relatively large distance needed to
accommodate the mirror during the heating step Consequently the
unsupported end portion of the fiber can flex during the heating
step, which may result in misalignment. This is particularly likely
when fusion-splicing single mode optical fibers. The cores of the
single mode fibers are only about 10 microns diameter (or even less)
and must be aligned very precisely. The required precision cannot
necessarily be achieved by aligning the exteriors of the fibers
because the cores might be slightly eccentric. It is then preferable
to align the exteriors visually as previously described and to align
the cores more precisely by passing a light signal from one to the
other across their juxtaposed ends and adjusting the alignment to
optimize the signal. However, surface tension effects may tend to
realign the exteriors as the fibers are fused together. If the cores
are indeed eccentric, they will then be misaligned when the fibers
are spliced.
The present invention seeks to eliminate, or at least
mitigate these disadvantages
According to the present invention, apparatus For
fusion-splicing two optical fibers comprises:
(i) a pair of supports, for example Vie grooves and
associated clamps; one for each fiber, arranged to support said
fibers in end-to-end relationship with their ends juxtaposed in a
region between the supports;
(ii) electrode means for generating a spark discharge
in said region;
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(iii) mirror means having a mirror surface inclined
relative to a common plane for the alignment axis of the fibers and a
predetermined viewing direction for reflecting a view of said fibers
in a direction transverse to said viewing direction; and
iv) means for displacing said mirror means in said
viewing direction between a first position close to the fibers,
wherein said view from the transverse direction is provided, and a
second position further away from the fibers and the viewpoint.
An advantage of this arrangement is that the mirror
moves away from the viewer so the fibers can be supported very close
to their ends to minimize flexing
The electrode means may comprise a pair of electrodes
disposed one etch side ox said region so as to define a spark path
substantially perpendicular to the alignment axis. The, or at least
one of the, electrode means may be movable away from said fibers at
least by an amount to provide a view of the corresponding mirror
surface unobstructed by such electrode. If a Vie arrangement of two
mirror surfaces is provided, both electrodes will be movable.
In preferred embodiments, however, only one mirror
surface is provided, and hence only the one corresponding electrode
is movable. With such an arrangement the single mirror surface may
be positioned so close to the fibers that the difference between the
optical paths direct from the fibers, and by way of the mirror, is
less than the depth of field of a microscope. Therefore the one view
of the fibers will be direct Leo in the viewing direction, and the
other via the mirror will be in the transverse direction.
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Advantageously, the mirror is inclined at 45 degrees to
the plane through the alignment axis of the fibers perpendicular to
said viewing direction and also intersects such plane. Thus the
reflected view is in the direction perpendicular to that of the
direct view.
The means for displacing said mirror may serve also to
displace the or each electrode. For example, said means for
displacing may comprise a plunger having its longitudinal axis, i.e.
axis of reciprocation, substantially aligned with said viewing
direction and cam means responsive to reciprocating movement of said
plunger for displacing said electrode laterally towards and away from
said zone.
In this specification, and the appended claims, the term
"alignment axis" is used for the imaginary axis with which the
longitudinal axes of the two fibers will coincide when they are
properly aligned. The position of this alignment axis will be
determined approximately by the support means but will vary slightly
due to differences in fiber external diameter and in core
eccentricity.
I An embodiment of the invention will now be described, by
way of example, with reference to the accompanying drawings, in
which:
Figure 1 is a side view of apparatus for fusion-splicing
two optical fibers;
Figure 2 is a schematic representation of a part of the
apparatus which is for moving one fiber transversely relative to its
length;
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I
Figure 3 is a sectional detailed view on line Z-Z of
Figure 1, and Figure PA a corresponding sectional side view;
Figure 4 is a view of the apparatus in the direction of
arrow X in Figure l;
Figure 5 is a plan view of -the apparatus;
Figure 6 is an opposite side view of the apparatus;
Figures 7 and are sectional detail views of a gripper
jaw of the apparatus taken on line Y-Y of Figure 5;
Figure 9 is a sectional side view taken on line C-C of
Figure 4;
Figure 10 is a sectional detail view showing the
electrodes in the closed position
Figure 11 is a view corresponding to Figure 10 but with
the electrodes in the open position;
Figure 12 is a side view of a modified gripper jaw;
Figure 13 is an exploded perspective view of the
modified gripper jaw; and
Figure 14 is a part-sectional view of a thimble for the
modified gripper jaw.
The apparatus illustrated in the drawings is for aligning
and fusion-splicing two optical fibers. Features of the apparatus
involved in manipulating the fibers are the subject of our cop ending
Canadian patent application serial number 440,995, filed herewith, in the
name of HUH. Lucas et at and entitled "Apparatus for Aligning an Artiste
Relative to a Datum". The apparatus comprises a support member or housing
10 formed from a block of aluminum. The front of the the block 10, i.e.
the face presented to the operator, is stepped from the top and front to
form a flat horizontal surface 12 and a generally flat vertical front
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surface 14. A generally rectangular recess 16 is formed in the left
side of the block 10, (as viewed from the front) and extends from the
bottom of the block 10 to a position adjacent the top of the block.
The recess 16 it central between the front and back of the block 10,
occupying about half the depth of the block in that direction. The
front wall 18 of recess 16 extends a short distance forward of a
continuation of the vertical surface 14.
A second block 19, of aluminum, comprising a first part
20~ a first arm 22, and a second arm 24, occupies the recess 16. The
profile of the second block comprising parts 20, 22 and 24, is
substantially the same as that of the recess 16, as can be seen from
Figure 1. The part 20 is securely anchored in the top of recess 16
by two securing screws 26 and 28. The latter I extends from the
left-hand side of the apparatus through anchorage part 20 into the
block 10 and the former (26) extends at about 45 downwards through
the rear corner of recess 16 into a threaded hole in part 20 so as to
draw part 20 tightly into the corner of recess 16.
The anchorage part 20, and arms 22 and 24, are formed
from a solid block, being delineated by suitably positioned holes and
slots. Thus, a hole 30 extends through the block 19 adjacent its
front and top, leaving a narrow neck portion 36. A slot 32, inclined
slightly to the horizontal, extends upwards from the rear face of the
block 19 to the hole 30. The slot 32 separates the part 20 from the
arms 22 and 24 except for narrow neck portion 36 between the hole 30
and the front face 14 of block 19.
From the lower end of neck portion 36, a short recess 38
extends at 45 downwards into the front face 14' of block 19. The
I
recess 38 has its upper sidewall 40 undercut at its lowermost part to
form a recess 42. A short web of material between the upper sidewall
40 of recess 38 and hole 30 thus forms a flexible hinge member 44
connecting arm 22 to anchorage part 20.
The bottom of recess 38 extends perpendicular to its
sidewall 40. A second hole 48 extends through the block 19 at a
position slightly below and rearwardly of the bottom surface 46 of
recess 38. A narrow portion of material between hole 48 and recess
38, of similar thickness to flexible hinge member 44, serves as a
second hinge 50 connecting the proximal part 52 of arm 22 (i.e. that
adjacent the hinge 44) to the second arm 24. A vertical slot 54
communicates at its upper end with hole 48 and extends between arms
22 and 24 to the bottom of block 10, permitting relative movement
between the arms 22 and 24 in the forward and rearward directions.
As can be seen from Figure 1, the front arm 24 is
separated from the front of the recess 16 by a clearance space 60 and
the rearward arm 22 separated from the rear face of the recess 16 by
a similar clearance 62. These clearances permit slight flexing of
the arms 22 and 24 to and fro.
As shown in Figure 2, the rear arm 22 has a
screw-threaded hole 64 extending through it from front to rear. The
hole 64 is aligned with a recess 66 extending into the rear face of
front arm 24. A spring 68 extends from recess 66 into hole 64 and is
retained therein by a cap screw 70 screwed into hole 64. The spring
68 acts between the bottom of recess 66 and the screw 70 to urge the
two arms 22 and 24 apart. The strength of the spring 58 is much
greater than the force required to flex the hinge members 44 and 50.
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Means for displacing top arms 22 and 24 to and fro
comprises eccentrically-mounted cam bearings 72 and 743 respectively.
(See Figure 2.) The cam bearings 72 and 74 cooperate with cam
follower pins 76 and 78, which comprise the ends of screws 80 and 82,
respectively. Screw 80 extends through the bottom end of rear arm 22
with its end projecting rearward and can be locked by a locking
screw 84 extending upwards into the bottom of the arm 22. Screw 82
extends through the bottom of arm 24, with its end projecting
forwards, and can be locked in a similar manner by a screw 86
lo extending into the bottom of arm 24.
The cam bearings 72 and 74 are coupled to pinions 88 and
I respectively, for rotation thereby. The pinions 88 and 90 engage
racks go and 94, respectively, which are connected to corresponding
conventional vernier screw mechanisms 96 and 98. The vernier screw
mechanisms 96 and 98 are anchored to the block 10 so that adjustment
of the vernier spindles 100 and 102 produces reciprocating movement
of the respective racks 92 and 94 relative to the block 10.
Both drive mechanisms are similar and one will be
described with reference to Figures 3 and PA which show
cross-sections through the rear part of the block 10. The drive
mechanism is housed in part by a housing 106 comprising a portion 110
of rectangular external shape which has its end reduced in
cross-section to form a circular spigot 112 which fits closely into a
hole 114 in the side of the block 10~ The spigot 112 is secured by a
key 115 in the form of a pin extending tangentially to the spigot
112. The key 115 has a curved indent 116 (see Figure PA) which
conforms to the surface of spigot 112. A screw 117, screwed into the
I
end of pin 115, urges it outwards, thus clamping the spigot 112
firmly in the hole 114.
The bearing cam 72 is mounted eccentrically on the
innermost portion of a shaft 118, which is supported by a pair of
bearings 120 and ]21, spaced apart by a spacer sleeve 123 around the
shaft 118. The shaft 118 extends into a round concentric cavity 122
in the outer end of rectangular housing portion 110. The gear pinion
88 is securely fixed to the end of shaft 118 in the cavity 122. The
housing 106 has a tubular part 124 which extends substantially
tangentially to the cavity 122 towards the front of the apparatus.
The vernier drive mechanism 96 is mounted coccal with the tube 124
so -that the rack 92 projects into the tube 124 and engages the pinion
MU. The vernier drive sleeve 126 fits into the forward end of tube
124 which is split to form a clamp 108 which is tightened by means of
screw 110.
In operation, rotation of the vernier thimble 100 as
indicated by arrow A causes movement of rack 92, which rotates
pinion 88, and therewith eccentric cam 72. The cam 72 displaces pin
76 to cause arm 22 to move to and fro. This will cause the proximal
portion 52 adjacent hinge 44 to pivot about the hinge 44, displacing
hinge 50 bodily in the direction of arrow 'A'. The part 130 of
second arm 24 proximal the hinge 50 therefore moves in the same
direction. This proximal part 130 has a recess 132 of rectangular
cross-section extending across it. Recess 132 serves as a mount for
a Vie groove 134 which will carry the optical fiber to be aligned.
The sidewalls of recess 132 extend at approximately 45 downwards
from the front face of arm 24. The sides of Vie groove 134 are
., 9
I
mutually perpendicular and coplanar with, respectively front face
14' of block 19 and the horizontal surface or apron 12 at the front
of the apparatus. When adjustment of vernier thimble 100 produces
movement of mount 130 in the direction of arrow 'A', the Vie groove
134 moves likewise, thus displacing the fiber transversely to its
length.
It will be appreciated that movement of the proximal
part 130 of arm 24 is only slight and is possible despite the fact
that forward movement of the lower end of arm 24 is prevented by cam
74. When movement of the vernier 96 produces a corresponding flexing
of the hinge 44 to move the mount 132 rearwardly, movement ox the
lower part of arm 24 is again prevented, but this time by the spring
68.
Adjustment of vernier 98, as indicated by arrow 'B',
will cause its rack 94 to reciprocate thus rotating the pinion 90 and
therewith eccentric cam bearing 74, which will cause movement of the
cam follower screw 82 in the lower end of arm 24. This will cause
the second arm 24 to pivot about its hinge 50. Movement of arm 22 at
its lower end is prevented by cam 72 and spring 68, tending to limit
movement of its proximal part 52, which is connected to hinge 50.
Thus the mount 132 and the Lee groove 134 will be moved primarily by
pivoting about hinge point 50 which, in the case of such smell
movements, can be considered as a linear movement in the direction of
arrow 'B', i.e. perpendicular to arrow 'A'.
Thus by adjustment of the two verniers 96 and 98, the
Vie groove 134 can be moved in two mutually perpendicular directions
'A' and 'B' relative to the longitudinal axis of the fiber in the
apex of the groove.
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Referring now to Figure 4, it will be seen that Vie
groove 134 is secured into its underlying recess 132 by two screws
140 and 142, respectively. Its inner end 144 extends in cantilever
fashion into a hole 146 which extends through the middle of block 10.
The hole 146 is of rectangular section and extends downwards at 45
to the horizontal, opening onto both horizontal surface 12 and the
vertical front face 14. Electrode assemblies 148 and 150,
respectively, disposed above and below the longitudinal axis of the
Vie groove 134 are mounted in a block 135 of finlike resin, slid ably
located in hole 146. The electrode assemblies comprise electrode
pins 176 and 178, respectively, which extend end-to-end either side
of the longitudinal axis of the fibers when held in the Vie grooves,
such that the longitudinal axis of the electrodes intersects that of
the fibers.
As shown in Figure 9, the electrodes are connected by
two wires 181 and 183, respectively, to an electrical supply (not
shown) which, in use, produces a spark discharge across the gap
between the ends of the electrodes. The spark discharge thus occurs
in the region of the juxtaposed ends of the two fibers and heats them
so that they can be fused together.
A second Vie groove 152 is mounted at the opposite
(right-hand as shown in Figure 4) side of cavity 146~ The Vie groove
152 is secured by a screw 154 into a corresponding recess and extends
with its inner end 156 projecting in cantilever fashion into hole 146
and in substantial alignment with Vie groove 134, i.e., the
corresponding surfaces of Vie grooves 134 and 152 are substantially
coplanar.
I
Before the fiber is inserted into the apparatus, the
outer coating is stripped away from its end for a short distance to
leave only the glass cladding and core.
The Use grooves 134 and 152 have grooves 158 and 160,
respectively, located in their apexes. The grooves 158 and 160
extend from the outermost ends to a position close to the ends
adjacent the center line 162 of the apparatus. The grooves 158 and
160 are of circular cross-sectior, and are arranged to be a close fit
for the optical fiber which has not had its outer coating stripped
away.
The cylindrical axes of grooves 158 and 160 are aligned
with the apexes of their respective Vie grooves 134 and 152. Small
rectangular recesses 168 and 170, respectively, extend transversely
across the part of the corresponding Vie groove between the end of
the groove 158 or 160 and the end of the Vie groove itself. The
recesses 168 and 170 each provide a seating for a respective one of
the interned ends of a pair of spring fingers 172 and 174,
respectively, which serve as grippers for the part of the fiber
located in the apex of the Vie groove, which has had its outer
coating removed.
The spring fingers 172 and 174 comprise leaf springs
mounted upon gripper arms 182 and 184, respectively. Gripper arm 182
is pivotal mounted in a slot 186 which extends into the apron 12
from its upper surface. The arm 182 is mounted upon a pivot pin 188
(see Figures 1, 7 and 8) which extends through the recess 186 with
its pivot axis parallel to the fiber axis
~231 39~
Leaf spring 172 is mounted at one end onto the gripper
arm 182 by a screw 183. When the arm 182 is in the closed position,
the interned end of leaf spring 172 rests in the recess 168, pressing
the exposed cladding part of the fiber into the apex of Vie groove
134.
The left-hand Vie groove 134 has a recess 190, its width
similar to that of recess 186, to accommodate the gripper arm 182
when the latter is pivoted into contact with the Vie groove. The
depth of recess 190 may be such that the gripper arm 182 serves as a
clamp to hold the coated fiber part into the circular groove 158 in
the Vie groove 134. The arm 182 is spring-loaded by a coil spring
192 (see Figure 7) which acts between the bottom of recess 186 and
the interior of a slot 194 in the gripper arm 182 to bias -the latter
into contact with the Vie groove 134. A pin 196 extends laterally
from arm 182 at a position below pivot pin 188. A push-pull or
connecting rod 198 is slid ably mounted in a hole 200 which extends
from the recess 186 towards the front of the block lo The push-pull
rod 198 is aligned with the pin 196 so that when the push-pull rod
198 is pushed into the recess 186, it contacts pin 196 and rotates
the gripper arm 182 out of contact with the Vie groove 134. When the
push-pull rod 198 is moved forwards, i.e. out of groove 186, the arm
1~2 returns to the closed position under the action of coil spring
192.
The push-pull rod 198 has a notch 204 at its forward most
end. The notch 204 accommodates the end 206 of a lever member 208
which is mounted in a slot 210 in the front of block 10. The slot
210 extends across the entire width of the block 10l Lever 208 is
Jo 13
:3L2~3~
secured in the slot by a pivot pin 212 extending vertically through
slot 210 at a position adjacent the right-hand side of block 10. The
distal part 214 of lever 208 projects outwards from the right-hand
side of the block 10 so that it can be pivoted to and fro about pivot
pin 212 by an operator. When the lever portion 214 is in the
rearward position, shown in full lines in Figure 5, the fiber is
clamped. When the lever is moved forwards to the position shown in
broken lines in Figure 5, push-pull rod 198 is urged into recess 186
to open the gripper jaw 186. When the arm 182 is fully open the pin
196 overrides the end of push-pull rod 198, as shown in Figure 8, so
arm 182 will only return to the closed position again when the
push-pull rod is moved forwards,
It should be noted that an operator can use his right
hand to move lever 208 and open the leFt-hand gripper arm 182 to
release the left-hand fiber He can then adjust the position of the
left-hand optical fiber using his left hand.
The mechanism for operating gripper arm 184 to open or
close the right-hand gripper spring jaw 174 is a mirror image of that
for operating the left-hand gripper jaw. Thus, a push-pull rod 216
extends through the front of the block 10 at the right-hand side and
engages the end 218 of a second lever 220, the distal end portion 222
of which projects from the left-hand side of block 10. The lever 220
is mounted above the lever 208 in the slot 210 in the front of block
10 and is pivotal about pivot pin 224 adjacent the left-hand side of
the block 10. Thus, the operator will use his left hand to operate
lever 220 to release the right-hand gripper mechanism, while using
his right hand to adjust the position of, or insert, the right-hand
optical fiber in the groove 156.
14
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Unlike the left-hand arm 182, gripper arm 184 it not
mounted directly into lock 10. Rather, arm 184 is mounted in a
recess 230 in the end of a lever 232. The lever 232 extends towards
the rear of the block 10 in a recess 234 in the right-hand side of
the block 10. The arm 184 is mounted upon a pivot pin 236 extending
laterally through the Levis formed by the recess 230 in the forward
end of lever 232, and has a pin (not shown) to be engaged by the end
of push rod 216 in like manner to that of the left-hand gripper jaw
mechanism.
The upper front portion of lever 232 is stepped to
provide a vertical surface 240 and a horizontal surface 242
substantially coplanar with the corresponding surfaces of the groove
156. The surfaces 240 and 242 have a central recess 244 to
accommodate arm 184 when it is in the clamping position such that the
pivot arm 184 will clamp the outer coating of the optical fiber into
the apex of the Vie groove formed by surfaces 240 and 242.
The lever 232 is pivotal mounted in the recess 234 by
a pivot pin 246 extending through suitably aligned holes in the block
10 and lever 232, respectively, from the underside of the block 10.
A recess 235 (see Figure 5) in the inner face of lever 232 houses a
return spring 248 which blesses the front portion of lever 232
outwards, i.e., towards the right as shown in Figures 4 and 5.
When the outer coating of the fiber is gripped by pivot
arm 184, pivotal movement of lever 232 about pivot pin 246 will cause
the fiber to be moved in the direction of its length. The fiber will
thus slide along the Vie groove 156, such movement being permitted by
the leaf spring 174. Longitudinal movement of the fiber is required
Z~3gL~
during the sequence of operations, in which the fibers are separated
slightly while being heated, then pushed together to cause their ends
to fuse.
Lever 232 is actuated by means of a mechanism at the
rear of block 10~ as illustrated in the cut-away view of Figure 5 and
in Figure 9. The mechanism comprises a cam 250 mounted upon a shaft
252 extending vertically in a cavity 254 at the rear of block 10.
The shaft 252 is mounted in bearings 249 and 251, respectively, and
is rotatable by a motor 253 located below a face plate 255 beneath
the block 10. The cam 250 is positioned adjacent a hole 256 which
extends between recess 254 and the recess 234 in the side of block
10. A ball 258 is located in hole 256 and serves as a cam follower.
The ball is in contact with the end of a screw 260 which extends
through a suitably screw-threaded hole 261 in the rear end of lever
232. A second screw, 262, extends through lever 232 from the outside
and is arranged to abut the bottom of recess 234. Screw 262 serves
to limit the movement of the rear part of arm 232 into the recess 234
when the cam 250 is rotated so that it is no longer in contact with
ball 258.
Screws 260 and 262 control the separation of the fibers
before and during the heating process by the spark discharge. Thus,
in the position shown in Figure 5, the lever 232 is in its initial
position ready for insertion of the two optical fibers. The operator
inserts the two optical fibers end-to-end after releasing the
gripping springs 172 and 174 as described previously. Initially, the
fibers are butted end-to-end such that the end surfaces meet in the
plane of the two electrodes 176 and 178. The fibers are then held
16
Lo
firmly by the gripping springs 172 and 174. The motor 253 is
actuated for a short time. The separation cam 250 rotates, its lobe
disengages ball 258 and allows the lever 232 to pivot inwards at the
rear until screw 262 bears against the bottom of the recess 254.
This gives the required separation of the ends of the fibers. The
slight separation is required to permit relative movement of the ends
of the fibers transversely to their longitudinal axes. The fibers
are then manipulated using the vernier mechanisms which move the Vie
groove 134 transversely relatively to the other Vie grow 156.
During initial alignment in this way, the relative positions of the
two fibers in the two directions 'A' and 'B' are observed with the
aid of a mirror 270 disposed beneath the spark Noah. The inclined
surface ox the mirror 270 extends towards the observer beyond the
axis of the electrodes, so that, when viewed in the direction of
arrow X of Figure 19 the mirror provides a lateral view of the two
fibers. The lower electrode 178 is movable away from the other
electrode to allow the mirror to be interposed. The mechanism for
moving the mirror will be described in more detail hereafter.
After initial alignment of the exteriors of the fibers
using such visual inspection, precise alignment of the cores is done
while monitoring the passage of a light signal across the gap between
the fibers. Circuitry for supplying and detecting the light signal
may be of conventional construction and so is not depicted.
Manipulation of the Fibers during the precise alignment stage using
the light signal is still carried out using the vernier mechanisms 96
and 98.
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A second cam 264 is mounted on shaft 252 at a position
slightly below cam 250. The lobe of cam 264 is diametrically
opposite that of cam 250. A second ball 265, in a corresponding hole
267, serves as a cam follower and acts between cam 264 and the end of
a third screw 266 which extends through the lever 232 at a position
slightly below screw 260. (See Figure 6.) Screw 266 has at its
outer end a head or knob 268 and carries a coil spring 271 which acts
between the surface of lever 232 and the underside of head 268 to
eliminate play and provide friction to ensure that undesired movement
of the screw 266 is prevented.
Once the fibers have been precisely aligned, the motor
is actuated to rotate shaft 252. Rotation of shaft 252 lowers the
mirror 270, restores electrode 178 to its operative position, and
closes a switch to initiate the spark discharge. During the spark
discharge, shaft 252 continues to rotate and, when the spark
discharge has heated the fibers sufficiently, cam 264 actuates the
associated ball 265 and displaces the rear part of the lever 232
outwards causing it to push the right-hand fiber back towards the
center line of the apparatus. In order that the fibers will fuse, it
is necessary for the right-hand fiber to be pushed beyond its
original position. The lift of cam 264 and position of screw 266 are
arranged to provide such additional movement. The extent of the
additional movement of the end of the right-hand fiber beyond the
axes of the electrodes may be adjusted by knob 268.
The electrode assemblies 148 and 150, their associated
operating mechanism, and the mirror 270 are shown in more detail in
Figures 9, 10 and 11. As previously mentioned, the electrode
I
assemblies 148 and 150 are mounted upon an insulator block 135 of
finlike resin material (or any other suitable insulating material)
in hole 146 in the middle of the block 10. A lamp 28Q is located in
a hole 282 extending from the upper, rear corner of block 10 to hole
146 at a position adjacent the electrode pins 17~ and 178 and serves
to illuminate them and the ends of the fibers.
The insulator block 135 is of 'I' cross-section and the
electrode assemblies 148 and 150 are accommodated one in each of the
two channels of the I section. The fixed electrode assembly 148
I (shown uppermost in Figures 1 and 4 and at the left in Figures 10 and
11) comprises an elongate brass bar 284 located at one end relative
Jo the insulator block 135 by a pin 286 extending through the flanges
of the block 135 adjacent its lowermost end. The end of the bar 284
has a notch 287 which engages the pin 286 to locate the bar 284
longitudinally. The bar 284 is biassed towards the central web
portion 288 by a leaf spring 294 which is attached to the bar 284 at
one end and bears against a terminal post 296. The bar 284 lies flat
against the central web portion 288 of the insulator block 135 and
protrudes slightly beyond the uppermost end of the web portion 288.
Electrode pin 176, of sistered tungsten or other suitable material,
extends transversely through the protruding end of bar 284 and is
secured thereto by a screw 290 extending into the end of the bar 284.
The tip of electrode 176 is arranged to be aligned with the
longitudinal axis of the fibers when they are correctly positioned.
An adjustment screw 291 extends into the bar 284 from one side to
impinge upon the electrode pin 176. This screw 291 permits small
lateral adjustments of tune electrode 176.
19
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A cylindrical handle 292, of insulating material, is
secured to the protruding end of bar 284 so as to extend beyond the
end of the insulator black 135. The electrode assembly 148 can be
removed by pulling the handle 292, the notch 287 disengaging the pin
286 with a "snap-action". Electrical connection to the electrode pin
176 is by way of the leaf spring 294 and terminal pin 296, which is
connected to the high voltage spark generator (not shown) by wire
181.
The movable electrode assembly 150 is similar in
construction to the fixed electrode assembly 148~ When in the
"spark-discharge" position, shown in figure lo it is a mirror-image
of electrode assembly 1~8, and comprises a corresponding set ox
components, namely an elongate brass bar 300, located relative to the
block 135 by d pivot pin 302 and having its own electrode pin 178
secured by a screw 304 to an end portion which carries an insulating
handle 306. Lateral adjustment of the electrode 178 relative to bar
300 is by means of adjustment screw 305. The electrical connection
is by way of a corresponding leaf spring 308 bearing against a
terminal pin 310, which is connected to the spark generator by wire
183.
The main difference is that the movable electrode
assembly 150 is pivotal about its locating pin 302 so as to displace
its electrode 178 outwards from the axis of the fibers. Such
displacement is achieved by means of a rod or plunger 314 which is
slid ably housed in a hole 316 extending through the central web
portion Z88 of the insulator block 135. The cylindrical axis of the
plunger 314, the fiber axes, and the spark discharge path between the
electrodes 176 and 178 are substantially mutually perpendicular.
LIZ
The plunger 314 is prevented from rotating by a pair of
set screws 318 which extend through opposite sidewalls of the web
portion 288. Each set screw engages a corresponding one of two flats
320 on opposite sides of the plunger 314. Only one set screw and one
flat are shown.
The lower end of the plunger 314 extends beyond the
insulator block 135 and has a surrounding flange 322. A compression
spring 324 carried by the plunger 314 acts between the end of
insulator block 135 and the flange 322 to urge the plunger 314
downwards i.e. away from the electrodes 176 and 178, to the position
shown in Figure 10. In this position, a cylindrical indent 326 in
the plunger 314 is aligned with an elongated hole 328 which extends
through the insulator block, including the web portion 288, adjacent
the electrode arm 300. A roller 330, of insulating material, located
in the hole 328 seats in the indent 326 and permits the arm 300 to
lie flat against the juxtaposed surface of web portion 288.
Consequently, the electrode 178 is in proximity to the fibers so that
spark discharge may take place.
It should be noted that, during the spark discharge, the
I end of plunger 314, which carries the mirror 270 (extending at 45 to
its longitudinal axis) is spaced well below the electrodes 176 and
178 to ensure that the mirror 270 is not spattered during the spark
discharge step.
When the plunger 314 is displaced towards the electrodes
176 and 178, against the action of spring 324, the roller 330 is
displaced out of indent or seating 326 and forces the electrode arm
300 away from the central web portion 288. This displaces electrode
:12~3~Z~
178 outwards to the position shown in Figure 11. At the same time,
the mirror 270 is repositioned in close proximity to the fibers, As
can be seen in Figure 11, the mirror 270 actually extends beyond the
plane occupied by the fiber axis and the spark discharge path. With
the mirror 270 in this position, the fibers can be viewed directly in
the direction of the longitudinal axis of the plunger 314. At the
same time, the image of the fibers in mirror 270 can be viewed,
giving the view of the fibers in a perpendicular direction i.e., in
the direction of the spark discharge path. The fibers can thus be
aligned visually. The plunger 314, and with it mirror 270, can then
be withdrawn, electrode 178 restored to its operative position, and
-the spark initiated
Displacement of the plunger 314 is by means of a third
cam, 334, on shaft 252. As shown in Figure 9, cam 334 acts against
the lower end of plunger 314. The shaft 252 also carries two cams,
336 and 338, respectively, beneath the faceplate 255. Cams 336 and
338 cooperate with corresponding limit switches 340 and 342 to
control the spark discharge and the motor cycle, respectively.
A significant advantage of the displaceable mirror
described herein before is that the mirror can be positioned very
close to the fibers during the alignment procedure. Consequently,
the optical path via the mirror 27~ is only slightly longer than that
direct from the fibers. Therefore both the fibers and their image
can be viewed without refocusing the microscope through which they
usually are viewed. This simplifies the operating procedure since it
is usual to focus directly upon the fibers to inspect their ends for
satisfactory cleaving and freedom from contamination, then carry out
22
, I; ,. . . .
~2~L3~24
the alignment. Another advantage of this configuration is that a
single planar mirror can be used which is much easier and cheaper to
make than the Vee-shaped mirrors used hitherto. Also, a single
mirror surface does not present problems of alignment with the fiber
axis and optical axis of the microscope, which might occur with
Vee-shaped mirrors in view of the precision required.
Various modifications are possible without departing
beyond the scope of the present invention. One particular
modification involves the gripper jaws and is illustrated in Figures
12 and 13. In the previously described embodiment the gripper jaws
comprise spring fingers 172 and 174, the interned ends of which bear
as knife edges against the fibers to clamp them into the apexes of
the Vie grooves.
In Figure 12~ a part of gripper arm 182 is shown. A
channel-shaped member 350 is secured to the end of the gripper arm
182 so as to extend parallel to the Vee-groove 134 and with its
channel facing away therefrom. A tappet member in the form of a
thimble-shaped member 352 is slid ably located in a hole 354 extending
through the base of the channel member 350 adjacent its distal end.
A wire spring 356 is secured at one end to the gripper arm 182 by a
screw 357, extends along the channel, and has its other end angled
into the thimble-member 352.
A cover plate 358, also secured at one end to the
gripper arm 182 extends along the mouth of the channel to cover the
wire spring 356. The spring 356 urges the thimble member 352 lightly
into contact with the fiber when the gripper arm is closed. It
should be noted that the end surface of the thimble-member 352 is
23
~2~3~
substantially flat so as to contact the fiber over a relatively large
distance. Moreover, the corresponding internal end surface of the
thimble-member 352 is formed as a conical seating 360. The end of
the spring 356 cooperates with the seating 360 to permit slight
pivoting of the thimble-member 352 to facilitate proper, flat
seating of the thimble-member 352 against the fiber.
Although the preferred embodiment has a single mirror,
inclined at 45, the invention still comprehends apparatus in which a
Vie mirror, or a pair of mutually-inclined separate mirror surfaces
are used to provide the two views of the fibers. Then both
electrodes will usually be movable to allow the mirror to be
positioned close to the fibers and/or to ensure they do not obstruct
the view of -the mirror surfaces.
Although particularly useful for single mode fiber, the
apparatus can be used to advantage with multimedia fiber. Moreover,
especially when aligning multimedia fiber, the light signal might be
dispensed with and the fiber position monitored solely visually
24
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