Methods of and apparatus for terminating a lightguide fiber ribbon

In terminating a ribbon which comprises an array of lightguide fibers, a substrate having a plurality of parallel grooves is positioned in a nest and supported at its end portions after which an end portion of the ribbon is moved longitudinally to cause the fibers to be separated by a comb-like device adjacent one end of the nest after which the ribbon is secured with a clamp adjacent the other end of the nest. Another substrate having aligned grooves is placed over the fibers so that the fibers are held in channels formed by the opposing grooves after which the assembly of substrates and fibers are secured together with a temporary clamp which applies compressive forces to end portions of the assembly along a longitudinal centerline of the assembly. Then a vise which includes jaws having parallel surfaces for engaging the substrate is moved toward the assembly to position a lower jaw under the lower substrate and an upper jaw above the upper substrate. Further motion between the jaws is caused to clamp together the substrates and is controlled to avoid damage to the assembly. The temporary clamp is disengaged from the assembly and the vise is removed to an environment wherein heat transfer into the vise is caused so that a potting compound applied to the assembly fills the interstices thereof to bond together the substrates and fibers.

TECHNICAL FIELD 
This invention relates to methods of and apparatus for terminating a 
lightguide fiber ribbon and, more particularly, for assembling a plurality 
of lightguide fibers of a ribbon with a pair of silicon chips. 
BACKGROUND OF THE INVENTION 
Lightguide fibers are now producible which in some applications compete 
favorably with other communication transmission media. This capability 
requires that economical splicing techniques be available for lightguide 
fiber systems. The splicing of fibers in an economic manner becomes an 
important problem to be overcome because the linking of two fibers require 
precise axial alignment and end separation. This becomes an even more 
acute problem in the splicing of a plurality of lightguide fibers of an 
array such as, for example, a fiber ribbon which may comprise twelve 
individual fibers. The problem in the mass splicing of a group of fibers 
is to position a first end of the array adjacent a similar end array so 
that corresponding fibers are all in precise axial alignment. 
A method and means for splicing arrays of lightguide fibers is shown in 
U.S. Pat. No. 3,864,018 which issued on Feb. 4, 1975 in the name of C. M. 
Miller. Optical fibers are aligned in highly precise and duplicatable end 
arrays by a substrate, which is called a chip and which has spaced, 
parallel fiber-receiving grooves and ridges on top and bottom surfaces. An 
array of fibers are held in aligned, opposing grooves of two chips which 
are referred to as positive chips and which are presently made of a 
silicon material. The assembly of positive chips and fibers is potted to 
maintain the precision geometry of the array. A splice includes a butt 
joint of two such arrays which are aligned with respect to each other by 
so-called negative chips which span over the butted positive chips on each 
side of the assembly. The negative chips each have a plurality of grooves 
and ridges which are aligned with the ridges and the grooves of the 
adjoining positive chips. In this way, the ridges of the negative chips 
are received in the grooves of the positive chips to maintain the 
geometry. Clips are installed about the assembly to secure together the 
chips. 
As should be expected, the groove geometry of the silicon chips is very 
important from the standpoint of controlling transmission loss. A 
discussion of the parameters of the chip which must be maintained within a 
one micron range is presented in an article by D. Q. Snyder entitled 
"Lightguide Connector Component Characterization" which was published at 
page 209 in the proceedings of the International Wire and Cable Symposium 
that was held on Nov. 13 through 15, 1979. 
It should be apparent that methods and apparatus must be provided to 
facilitate the rapid fabrication of optical ribbon splices. A 
vacuum-assisted silicon-chip multiple fiber chuck which has been developed 
for assembling a plurality of lightguide fibers between a pair of the 
positive silicon chips is described in an article by A. H. Cherin et al 
entitled "Vacuum-Assisted Silicon Chip Multifiber Chuck" as published in 
Vol. 16 of Applied Optics in June 1977. The lightguide fibers are fanned 
out and moved into the grooves of one of the positive silicon chips after 
which the other chip is placed thereover and the assembly held together 
manually while it is potted. 
What is still needed is the capability of assembling a plurality of 
lightguide fibers between two substrates to terminate a lightguide ribbon 
with assurance that the fibers are positioned within their respective 
grooves in the substrates during the assembly and that they will be 
retained within their respective grooves during the potting operation. 
This would facilitate field termination as well as allow the factory 
connectorization of lightguide fiber cable so that field personnel need 
only arrange the terminated ends of ribbons between negative chips and 
secure the chips together. 
SUMMARY OF THE INVENTION 
The capability of terminating a lightguide fiber ribbon is provided by this 
invention which includes methods of and apparatus for assembling a 
plurality of lightguide fibers with a pair of fiber-receiving substrates. 
A method of this invention for terminating a plurality of lightguide 
fibers which extend from a lightguide fiber ribbon includes the steps of 
supporting a first substrate at opposite end portions of the substrate in 
a nest at an assembly station, the substrate having a plurality of spaced 
parallel fiber-receiving grooves formed in at least one side thereof with 
the grooves oriented upwardly and spacing apart a plurality of lightguide 
fibers which extend from a lightguide ribbon beyond one end of the 
substrate with the ribbon extending beyond the opposite end of the 
substrate. Then the ribbon is moved in a direction along its longitudinal 
axis so that each of the individual fibers is pulled into and along one of 
the fiber-receiving grooves of the substrate after which a second 
substrate having a plurality of fiber-receiving grooves is positioned in 
engagement with the fibers with the grooves of the second substrate facing 
the grooves of the first substrate to enclose each of the fibers in a 
passageway formed between opposed aligned grooves in the first and the 
second substrates. Compressive forces are applied to the assembly of the 
first and second substrates and the plurality of lightguide fibers at end 
portions of the assembly above the supported end portions of the first 
substrate and substantially along a longitudinal center line of the 
substrates to hold together the assembly. One jaw of a vise is moved into 
juxtaposition with a lower surface of the first substrate and another jaw 
of the vise into juxtaposition with an upper surface of the second 
substrate after which the assembly is secured together by causing the jaws 
to apply a predetermined compressive force to the assembly. The 
application of the compressive forces to the end portions of the assembly 
is discontinued and an encapsulating material is applied to the assembly, 
said encapsulating material being adapted to fill interstices between the 
fibers and the substrates to hold together the assembly of the fibers and 
the substrates. 
In a preferred embodiment, the method also includes the step of causing the 
first and second substrates to be laterally and longitudinally confined in 
said nest and prior to the step of applying an encapsulating material, the 
method includes the step of removing the lateral and the longitudinal 
confinement of the substrates. This facilitates a lowering of the nest out 
of supportive engagement with the assembly without unduly stressing the 
assembly.

DETAILED DESCRIPTION 
Referring now to FIG. 1, there is shown an apparatus 20 of this invention, 
said apparatus being capable of terminating a plurality of lightguide 
fibers 21--21 of an array 22 (see FIG. 2A) between a pair of positive 
substrates 23--23 (see FIG. 3) of a cable 26 or a cable 27. Each of the 
substrates 23--23 is a silicon chip which is referred to as a positive 
chip and which has been etched to produce a plurality of longitudinally 
extending, parallel grooves 24--24 having a precise geometrical 
configuration. A description of the geometry of the chips and their use in 
terminating lightguide fiber arrays is well described in the priorly 
identified article by D. Q. Snyder which was presented to the 1979 
International Cable and Wire Symposium. 
The apparatus 20 includes a base plate 31 having a support 32 for holding a 
lightguide fiber ribbon 22. The support 32 includes a channel 34 in which 
an assembly person positions the ribbon 22 with individual ones of the 
exposed fibers 21--21 extending beyond a right hand end of the channel as 
viewed in FIG. 4. 
Side walls 36--36 of the support 32 which form the channel 34 have openings 
37--37 formed therein for receiving a clamping pad 38 that is attached to 
one end of a threaded rod 39 that extends through an end 41 of a link 42 
that is mounted pivotally by a pin 43 in a bearing 44. A clamping lever 46 
has one end 47 pinned at 48 to the link 42 and is connected by a pin 49 to 
a link 51 that is connected by a pin 52 to a second bearing 53. The 
bearings 44 and 53 are mounted on an upper portion 54 of a stand 56 that 
is supported on the base plate 31. 
As can be seen in FIGS. 1, 4 and 5, a support, which is designated 
generally by the numeral 61, for a substrate 23 such as, for example, a 
silicon chip is positioned on the base plate 31 just to the right of the 
support 32. The support 61 includes a block 62 having a channel 63 formed 
therein and aligned with an opening 65 in the base plate 31. The channel 
63 is adapted to have a post 64 mounted slidably therein. The post 64 has 
a pin 66 extending therethrough with a collar 67 mounted thereon adjacent 
a side 68 of the post. On the other side of the post 64, the pin 66 
extends through a vertical slot in the block 62 and a generally 
horizontally disposed slot 69 in an ear 71 that extends from a plate 72 
which is mounted rotatably on a shaft 73 that extends from the block 62. 
The ear 71 could just as well be mounted on the portion of the pin 66 
adjacent the collar 67. The plate 72 has a handle 74 which is adapted to 
be moved to turn the plate 72 and cause the ear 71 to be turned to move 
the post 64 upwardly or downwardly. 
In order to provide a rack or nest 81 for a silicon chip 23, an upper 
portion 85 of the post 64 is generally U-shaped with end legs 82--82 
upstanding from a horizontally disposed surface 83. Also, a pair of side 
plates 84--84 having overhanging portions 86--86 are mounted laterally of 
the post on a threaded fastener 87. The fastener 87 has a head 88 for 
turning the fastener to hold the side plates 84--84 in engagement with the 
post 64. It should be observed from FIG. 5 that each side plate is also 
U-shaped with a pair of spaced legs 89--89. The cross-sectional 
configuration of each of the legs 89--89 is stepped (see FIG. 6) such that 
an outer distance "d.sub.1 " between corresponding, opposing legs of the 
two side plates at their outer ends is less than an inner distance 
"d.sub.2 ". This arrangement provides a nest for a silicon chip 23 and 
holds the chip while preventing inadvertent longitudinal movement through 
the engagement of corners of the chip with portions of the steps. 
After an operator positions a lightguide ribbon 22 with the individual 
fibers 21--21 extending beyond the chip support 61, the fibers are fanned 
out between partitions 91--91 of a combing device which is designated 
generally by the numeral 92 (see FIG. 4). The partitions 91--91 are 
generally rectangular and maintained spaced apart by separators 93--93 
which are L-shaped with an upstanding leg 94 connected to a horizontal 
portion 96. The horizontal portions 96--96 are spaced a substantially 
greater distance from the top edges of the partitions 91--91 than are the 
tops of the upstanding legs 94--94. 
The partitions 91--91 are relatively thin blade-like pieces of polished 
steel which are alternated with the separators 93--93. Advantageously, the 
upstanding legs 94--94 of the separators 93--93 provide stability for the 
upper, generally unsupported portions of the partitions 91--91. The 
assembly of partitions and spacers are held between side plates 97--97 
that extend upwardly from feet 98--98 that are attached to a top plate 99 
of a slide 101. The slide 101 may be one which is commercially available 
from Design Components Inc. of Medfield, Mass. 
The slide 101 is adapted to be moved slidably from left to right as viewed 
in FIG. 4 to initially position the comb adjacent to the chip support 61 
to receive the fibers 21--21 between the partitions 91--91 and 
subsequently to be moved from the chip support to provide additional room 
about the nest 81 for additional operations. The slide 101 is U-shaped 
with a top portion 102 to which is attached the top plate 99 and depending 
side portions 103--103 to form a way 104 for a rail 106 that is mounted on 
the base 31. The rail 106 includes lateral V-shaped grooves 107--107 for 
holding roller bearings (not shown) between the rail and the depending 
side portions of the slide. 
A temporary clamp 111 (see FIG. 7) is used to hold together the assembly 
until other facilities have been moved into position to perform that 
function. The temporary clamp 111 includes a main body portion 112 having 
a keyhole-shaped opening 113 formed therethrough so that the clamp can be 
mounted on a stepped post 114 that extends vertically upward from the base 
plate. A threaded pin 115 is turned into the body portion 112 by a knurled 
headed end 116 to cause its free end to enter the opening 113 and engage 
the post to lock the clamp to the post. The clamp 111 also has a pair of 
outwardly extending fingers 117--117 made of spring steel and having pads 
118--118 attached to the ends thereof. The pads 118--118 are shaped to 
project toward each other and between the opposing uprights of the stand 
to engage the top positive chip. This of course applies compressive forces 
to end portions of the assembly which spans between end portions of the 
stand. Because of the material of which the fingers 117--117 are made and 
their dimensions, the pads 118--118 are self-adjusting and are not 
sensitive to the mounting of the body portion 112 on the post. 
The temporary clamp 111 also is formed to insure that the application of 
compressive forces to the assembly of the chips 23--23 and fibers 21--21 
is accomplished to avoid the inadvertent displacement of one or more of 
the fibers from their grooves. Such a displacement would occur if the 
forces were applied through surface-to-surface contact of the surfaces 
formed on the pads 118--118 with the top surface of the top chip 23. In 
order to avoid this and as shown in FIG. 8, the surfaces of the pads 
118--118 are formed with a curvature to apply line contact forces to the 
top chip 23 at opposite ends of the top chip and generally along its 
longitudinal centerline. 
If these last mentioned precautions were not taken and forces were applied 
through surface-to-surface rather than through line contact, the top chip 
23 could become canted with respect to the lower chip which would cause 
the top chip to possibly become disengaged from one or more of the fibers 
21--21. This would result in inadvertent lateral movement of the fibers 
21--21 out of the grooves 24--24 in the bottom chip 23. 
After the assembly of the bottom silicon chip 23, lightguide ribbon 22 and 
top silicon chip 23 has been made, provisions are made for securing 
together the elements of the assembly in such a way that the secured 
assembly may be removed from the apparatus 20 and potted. A vise 
designated generally by the numeral 120 (see FIGS. 1 and 9) includes an 
L-shaped frame 121 having a stepped vertical leg 122. The clamping of the 
assembly is accomplished with a top clamp 123 which includes an upper 
portion 124 that has a trapezoidal cross-section with its longer base 
adjacent a vertical face of the frame 121. The portion 124 is adapted to 
be moved slidably between side guides 126 and 127 which are fastened to 
the frame 121 and which are tapered inwardly to form a way 128 that is 
adapted to receive the portion 124. A top member 131 spans across the 
guides 126 and 127 and has a threaded rod 132 extending therethrough and 
turned into the portion 124. A torque limiting thumbwheel 133 is attached 
to the upper end of the rod 132 to allow an operator to cause the portion 
124 to be moved upwardly or downwardly. 
A lower portion 136 of the top clamp 123 has a jaw 137 that is adapted to 
clamp the assembly between it and a lower jaw 141. The lower jaw 141 
comprises an insert 145 (see FIG. 10) that is supported in a U-shaped 
opening 142 of an arm 143 that is cantilevered out from a T-shaped plate 
that is secured to an underside of the frame 121. 
The thumbwheel 133 and rod 132 arrangement for moving the jaw 137 toward 
the lower jaw 141 is force limiting which results in slippage between the 
rod and the thumbwheel 133 after a predetermined torque has been applied 
to the rod when the two jaws are in engagement with each other. This 
arrangement prevents the application of unduly high compressive forces to 
the assembly of the chips 23--23 and the fibers 21--21. 
Care is taken in order to insure that the upper and lower jaws 137 and 141 
of the vise 120 are substantially parallel to each other. Initially, the 
insert 145 is set in a bed of epoxy resin within the arm 143 and the upper 
jaw moved downwardly into compressive engagement with it. A set screw 146 
is moved upwardly through the T-shaped plate 143 forcing the insert 145 
into planar engagement with the upper jaw 137. This engagement is 
maintained until the epoxy resin cures whereupon the upper jaw is moved 
upwardly leaving its face substantially parallel to that of the insert 
145. 
The vise 120 is adapted to be mounted on a carriage designated generally by 
the numeral 151 so that it may be moved transversely toward or spaced from 
the chip support 61. The carriage 151, which may be one such as the slide 
101 which is available from Design Components, Inc., includes a top plate 
152 that is attached to a U-shaped portion 153 having an opening 154 
therethrough. The top plate 152 includes two spaced pegs 156--156 which 
are adapted to be received in the apertures in the foot of the L-shaped 
frame of the vise 120. Inner side walls of the U-shaped portion 154 which 
form the opening 154 include longitudinally extending grooves into which 
project roller bearings that are mounted in adjacent side walls 157--157 
of a guide rail 158 that is received within the opening 154. 
Again referring to FIG. 1, it can be seen that a compression spring 155 is 
received in an opening 159 in the top plate 152. This spring 155 extends 
into an alinged opening at the lower portion of the vise 120. As the vise 
120 is moved with the carriage 151 inwardly toward the nest, the spring 
155 is such that the vise base is spaced slightly above the top plate of 
the carriage 151, but also such that the lower jaw 141 may be moved under 
the lower chip. The spring 155 is effective to counteract the vise weight 
and is effective to counter the downward forces exerted against the vise 
when the thumbwheel 133 is turned to cause the upper jaw to be moved 
toward the lower jaw. 
The apparatus 20 also includes provisions for precisely positioning the 
vise 120 so that its jaws 137 and 145 underlie and overlie the chip 
assembly. An adjustable stop 161 extends laterally of the block 62 a 
predetermined distance so that when it engages a front side of the 
U-shaped portion 154 of the carriage 151, the jaws of the vise are 
positioned above and below the chip assembly. Further, a slide 164 having 
two slotted openings 166--166 is mounted for sliding movement transverse 
of the direction of motion of the carriage 151. Fasteners 167--167 extend 
through the openings 166--166 into the base plate and allow the slide to 
be moved to position a latch 168 to be moved behind the U-shaped portion 
153 to retain the carriage 151 in its forward, clamping position while its 
jaws are being engaged with the chip assembly. 
In the termination of a single ribbon 22, a positive chip 23 is positioned 
in the nest 81 supported in engagement with the surface 83 and with its 
corners in engagement with the steps of the legs 89--89. Then the ribbon 
22 with end portions of the fibers 21--21 exposed is positioned in the 
channel 34 with the end portions of the fibers disposed between the 
partitions 91--91 of the comb 92 which is positioned adjacent the chip 
support 61 as shown in FIG. 4. The ribbon 22 is pulled to the left as 
viewed in FIG. 4 to cause the fibers 21--21 to be moved between the 
partitions 91--91 and into the grooves 24--24 of the lower chip 23. The 
ribbon 22 is clamped in the channel 34 and a visual check is made to 
determine that all fibers 21--21 are seated individually within their 
respective grooves 24--24. Then the upper chip 23 is positioned over the 
fibers 21--21 such that the fibers are received in its grooves and such 
that the corners of the chip are in engagement with the stepped legs 
89--89. The comb 92 is moved to the right as viewed in FIG. 4 to space it 
from the chip support 61 to provide access for checking the seating of 
each fiber 21 between two grooves 24--24 and to provide additional room 
for subsequent operations. 
The temporary clamp 111 is mounted on the post 114 and lowered until the 
pads 118--118 which protrude between opposing pairs of legs 89--89 engage 
the ends of the upper chip 23 at its ends. Because of the curvature of 
their lower surfaces, the pads 118--118 apply line contact compressive 
forces to the assembly of chips 23--23 and fibers 21--21 generally along a 
longitudinal axis of the assembly and at end portions of the assembly over 
the top of the legs 82--82 on which the assembly is supported. The knurled 
headed end 116 is turned to cause the temporary clamp 111 to be attached 
to the post 114 such that the compressive engagement of the pads 118--118 
with the assembly is maintained. 
Next, the carriage 151 is moved unitl it engages the stop 161 which causes 
the jaws 137 and 141 of the vise 120 to be positioned above and below the 
assembly in the nest 81. Since the assembly is supported as a beam between 
the legs 82--82 of the U-shaped center section of the nest 81, the lower 
jaw 141 of the vise 120 is capable of being moved under the assembly. The 
thumbwheel 133 is turned to cause the upper jaw 137 to be moved downwardly 
to clamp the assembly between it and the lower jaw. As should be apparent, 
this clamping of the assembly is accomplished between the pads 118--118 of 
the temporary clamp 111. 
After the vise 120 has been caused to clamp together the assembly, the 
temporary clamp 111 is removed from engagement with the upper substrate 
23. The head 88 is turned to loosen the engagement of the side plates 
84--84 with the U-shaped center plate 85 and with the assembly. When the 
handle 74 is moved clockwise as shown in FIG. 4 to lower the nest 81, the 
release of the side plates 84--84 permits the disengagement of the chip 
support 61 from the assembly without stressing the assembly. The ribbon 22 
remains in the channel 34 and the assembly supported and held clamped in 
the vise 120. 
The assembly of chips 23--23 and fibers 21--21 is now ready to be potted 
with an epoxy resin material. The pad 38 is caused to be disengaged from 
the ribbon 22 and the vise 120 together with the ribbon is removed from 
the apparatus 20. The vise 120 is placed in engagement with a heating 
device (not shown) such as a hot plate to cause heat transfer into the 
jaws 137 and 141 and into the assembly. The vise 120 may be constructed 
with a short length of rod 171 made of a material having a relatively high 
thermal heat conductivity to facilitate heat transfer into the vise. After 
a predetermined temperature is reached, an epoxy resin material is applied 
to the chips 23--23 and is caused to flow into and fill the interstices 
between the fibers 21--21 and the walls of the grooves 24--24. The 
assembly is then moved to another work station where its free end is 
ground and polished to facilitate field or factory connectorization. 
The above-described embodiment is used to terminate a simple lightguide 
fiber ribbon which generally comprises twelve fibers. The apparatus 20 may 
be modified as shown in FIGS. 11 and 12 to include a different ribbon 
clamp and a different temporary clamp than those used in the 
above-described embodiment so that it can be used to terminate a stack of 
ribbons 22--22. First, turning to facilities for clamping a cable 27 (see 
FIG. 2B) having an array of ribbons, a ribbon clamp designated generally 
by the numeral 201 which comprises part of the modified apparatus as shown 
in FIG. 13 and includes a pair of side plates 202--202 spaced apart by a 
base 203 and a rod 204. 
Each of the plates 202--202 is formed with a pair of arcuately shaped slots 
206 and 207 with the slots 206--206 and 207--207 being aligned. The slots 
206 and 207 are adapted to receive pins 208--208 and 209--209 that extend 
laterally of a clamping finger 211 having a hooked end 212. The finger 211 
includes a frontal pad 213 that is adapted to engage a top portion of the 
array of stacked ribbons when the array is received in the channel. A 
lower portion of the finger 211 is bifurcated with a shaft 214 extending 
between those portions. A tension spring 216 has one end secured to the 
shaft 214 and a lower end secured to a shaft 217 that extends between the 
side plates adjacent to the base. 
The slots 208--208 and 209--209 are arranged and configured so that an 
operator must apply downward and horizontal forces to the hooked end 212 
to cause the pins 208--208 and 209--209 to be moved in the slots 206--206 
and 207--207 to the lowermost portions of the slots. When the clamp is in 
that position, the spring 216 holds the pad 213 in engagement with the 
array. To disengage the pad 213 from the array, the operator pulls the 
hooked end rearwardly and upwardly to cause the pins to move along their 
respective slots and become locked in the rear portions thereof. 
Going now to facilities for temporarily clamping the array, there is shown 
in FIG. 14 a device 231 that comprises a block 232 having one end 235 that 
is lower than another end 233. An opeing 234 is formed vertically through 
the block so that the block can be mounted on the post 114 upstanding from 
the base plate. A T-shaped clamping member 236 is attached to the inner 
end of the block with the stem 237 of the T projecting toward the stack of 
ribbons 22--22 and chips 23--23. A spring-like finger 238 is attached to 
the underside of the stem. As each ribbon is moved donwardly into the nest 
into superimposed relation to foregoing chips and ribbons, it deflects the 
spring-like finger and the block 232 is indexed to successively higher 
positions on the post 114. 
In the use of the modified apparatus 20 for terminating a stack of ribbons 
22--22 of a cable 27, a chip 23 is positioned in the nest 81 spanning 
between the upper surfaces of the legs of the U-shaped center section 85 
and then one ribbon of the stack is terminated as described hereinbefore 
for the single ribbon. Of course, now the ribbon clamps 201--201 are used 
to engage the stack. After the lowermost ribbon has been terminated 
between a lower chip 23 and an upper chip, the grooves in the upper 
surface of the upper chip become starting grooves for the next successive 
ribbon in the stack. After all the ribbons 22--22 in the stack have been 
terminated, the assembly of chips and fibers is clamped by the vise 120 as 
before and removed for potting. 
Turning now to FIG. 15 there is shown another embodiment of the vise 120. A 
vise designated generally by the numeral 250 includes all the elements of 
the vise 120 but also includes an auxiliary clamp 251. The clamp 251 
includes an arm 252 having an upper portion 253 which is supported from 
two fasteners 254--254 that extend through slotted openings 256--256 in 
the upper portion and into the moveable post of the vise. A lower portion 
257 of the clamp 251 depends downwardly from a horizontal portion 258 and 
includes a pad 259 designed to cooperate with a lower pad 261 supported 
from a cantilevered arm 262. The pads 259 and 261 are made of a 
rubber-like material. 
The clamp 251 is designed to have its pads 259 and 261 engage portions of 
the ribbon 22 having its fibers 21--21 extending into the nest. In this 
way when the vise 250 is removed from the apparatus for the potting step, 
undue flexing of the ribbon of fibers in the assembly is prevented thereby 
avoiding possible cracking of the fibers at their entrance to the chips 
23--23. 
The foregoing methods of this invention have been described to include the 
step of removing the vise 120 with the assembly of substrates and fibers 
clamped between the jaws of the vise to another work station where a 
potting compound is applied to fill the interstices between the fibers and 
the grooves. It should be realized that in some applications, the 
disengaging of the nest 81 from supportive engagement of the assembly by 
lowering of the nest allows sufficient space about the assembly as held in 
the vise to perform the potting operation. 
It is to be understood that the above-described arrangements are simply 
illustrative of the invention. Other arrangements may be devised by those 
skilled in the art which will embody the principles of the invention and 
fall within the spirit and scope thereof.