[0001 ] METHOD FOR TRANSFERRING A LARGE NUMBER
OF FIBER ENDS INTO A SPECIFIED POSITION
[0002] BACKGROUND
[0003] The invention concerns a method for transferring a large number of fiber
ends of a bundle of optical waveguides, especially glass, quartz or plastic fibers, into a
large number of specified positions with an alignment apparatus which includes
openings which vary in size in a specified range as well as a method for manufacturing
a glass, quartz or plastic fiber ends which are connectable with a plug arrangement.
[0004] With glass fiber cables with a great number of glass fibers, it has up until
now been customary to grasp the individual fibers manually and transfer them
individually into a specified position.
[0005] In this way, for example, glass fibers could be arranged lying alongside
one another, in a one dimensional array, and joined together to form a plug connector
for a glass fiber cable.
[0006] The disadvantage in a process of this type was that this process is very
expensive for an exact positioning of many glass, quartz and plastic fiber ends.
[0007] In particular, a process of this type does not permit transferring a two-
dimensional glass fiber array with, for example, 2 x 2 to 40 x 40 glass fibers, into a
connector so that a glass fiber cable with a large number of glass fibers in a two
dimensional, for example square or rectangular matrix results. In particular, the
processes according to the state of the art did not allow a very exact positioning, in the
range of a few micrometers (μm), of a large number of closely spaced glass fiber ends.
[0008] SUMMARY
[0009] Consequently, it is the object of the invention to provide a method with
which these disadvantages can be overcome, especially to provide a method which
makes possible a very exact positioning in a two dimensional matrix with a spacing
between the fiber ends of a few μm. In particular, in this way, a simplified point-to-
point arrangement of two glass fiber ends is made possible. Furthermore, the
procedure should permit an extensive automation in connection with the manufacture
of glass fiber cables.
[0010] In accordance with the invention, this is achieved in that the fiber ends
are passed through the openings of an alignment apparatus, in which the size of the
openings have been selected such that at most one fiber end of a glass fiber, preferably
without a protective layer, can pass through an opening. In a second step, the size of
the openings are reduced so that the fiber ends arrive at the specified positions.
[0011] The advantage of a solution of this type is especially that the individual
fibers can be transferred into positions lying very close alongside one another since
with such a process very close distances, as, for example, are specified by the bar
widths of an alignment apparatus, no problems arise in connection with positioning.
[0012] With such a method, glass fiber ends can be brought exactly into a
position up to < ± 2 μm, whereby the individual glass fibers with core, cladding and
protective coating can have a diameter of from 20 μm, and preferably 100 μm to 1000
μm, and most preferably 260 μm. The stripped glass fiber ends without protective
coating include a core and cladding and can have a diameter in the 50 to 800 μm
range.
[0013] One configuration for the alignment apparatus is constructed in the form
of a perforated plate, whereby the individual openings are formed by bars. In a first
position, the size of the opening is selected such that at most a stripped glass fiber end
without protective coating can pass through. This provides, in comparison to a
perforated plate having fixed distance openings, a relatively large-meshed net. The
bars are slidable to a second position, in which they define a fine-meshed net where
each position of the individual openings corresponds to the desired position of the
glass fiber end in a glass fiber array.
[0014] Preferably, distance between bars is selected to be < 105 μm in the first
position and < 95 μm in a second position. The diameter of the individual bars
corresponds to the standard distance between the individual glass fibers in the desired
glass fiber matrix.
[0015] The alignment apparatus of the invention with flexible matrix permits,
first of all, the individual fibers to be able to be introduced into a relatively broad
opening, the size of which must be selected so that in the first position, the entry of a
second fiber is prevented. The opening size for exact positioning of the individual
fibers is then selected such that the spacing between the bars corresponds to the
diameter of the glass fiber ends.
[0016] A solution of this type has, for example, in comparison with a fixed
matrix, the advantage that it can almost be ruled out that individual fibers do not
extend through the holes and must be repositioned in an expensive repair process in
the traditional manner.
[0017] A further advantage is that the fibers can at the same time be guided by
several alignment apparatuses, whereby the size of the openings of each individual
alignment device is individually adjustable.
[0018] Passing the fiber ends through the coarse-meshed net is assisted by the
glass fiber ends and/or the alignment apparatus being periodically moved, especially
set into vibration. This can take place by shaking.
[0019] In addition to the method of the invention for positioning, the invention
also provides a method for manufacturing glass fiber ends to form a plug connection
which includes a large number of individual glass fibers.
[0020] Only with an assembly technique of this type is it possible to make
available a glass fiber cable at a reasonable manufacturing expense with a two
dimensional glass fiber array which can be used, for example, in the area of optical
data communication.
[0021] A process of this type for manufacturing glass fiber ends which can be
used to form a plug connection includes the step of positioning the individual glass
fibers with the aid of the method of the invention, into a preliminary alignment of the
fiber ends and then into a final fixed arrangement. The final fixed arrangement of the
fiber ends can, for example, be attained by filling the spaces between the fiber ends
with a casting or potting material and subsequent hardening. This final fixed
arrangement can, for example, be incorporated into a plug connector.
[0022] After introducing such an end of a glass fiber cable with glass fibers
which are arranged in a two dimensional matrix into a plug arrangement, it is
necessary for a sufficient optical quality connection, for the glass fiber ends of the
glass fibers to be ground and polished so that the glass fiber array defines a smooth
plane.
[0023] For a sufficiently good positioning in a glass fiber array, it is necessary
for the glass fiber ends to be individual glass fibers without any protective coating.
That is, the glass fiber ends are merely comprised by the glass fiber core and the glass
cladding.
[0024] Preferably plastic and/or an adhesive are used as casting or potting
material.
[0025] BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention is to be described below on the basis of the preferred
embodiments. Although the preferred embodiments relate to glass fibers as optical
waveguides, the method of the invention can also be used on other optical wave
guides, such as, for example, quartz or plastic fibers, without deviating from the
invention.
[0027] In the drawings:
[0028] Figure 1 is a side elevational view of a preferred construction for
implementing the method of the invention whereby the passage of the glass fiber ends
through the openings of the alignment device is assisted by motion,
[0029] Figure 2A is a plan view of the alignment apparatus with spacers which
in the closed state guarantee a defined distance, whereby the bars are situated in a first
position, to produce a coarse-meshed net,
[0030] Figure 2B is a plan view of the alignment apparatus of Figure 2A with
spacers, whereby the bars are in the second position, producin the fine-meshed net,
and
[0031] Figure 3 is a perspective view of a glass fiber cable manufactured using
the method of the invention with a large number of glass fibers arranged in a two
dimensional matrix.
[0032] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] Figure 1 shows a preferred structure for positioning a large number of
glass fiber elements with the aid of an alignment apparatus 3 with variable openings.
[0034] Clearly recognizable is the great number of glass fiber ends 1 of the
glass fiber cable. Each individual glass fiber of the glass fiber cable is formed of a
glass fiber core, a cladding or cladding glass, as well as a protective layer which
surrounds the cladding or cladding glass.
[0035] For positioning the individual glass fiber ends 1 of the glass fibers in
accordance with the method of the invention, the protective layer is removed from the
individual glass fibers in the region of the fiber ends 1. The individual glass fiber ends
1 are transferred to an alignment apparatus 3 which is constructed generally in the
form of a perforated plate formed from individual bars, whereby the bars of the
invention can be moved to provide a variable bar distance so that openings with
various opening diameters are formed.
[0036] The opening size is so dimensioned in a first position that preferably at
most one fiber end, including core and cladding, but not the protective layer, can pass
through the opening. The perforated plate is a relatively coarse-meshed matrix in this
position.
[0037] If now the bundle 5 of fiber ends 1 is placed on the perforated plate 3,
then the individual glass fiber ends 1 pass through the openings and are roughly
positioned.
[0038] Due to the large openings, 100% of the stripped fiber ends fall through
the openings and can thus be prepositioned.
[0039] Should all the holes not be filled and individual fibers of the great
number of glass fibers not pass through the perforated screen, these individual fibers
can be manually reprocessed.
[0040] To come from the very crude positioning to the very closely toleranced
array, the individual wires which form the bars can be pushed together. The tolerance
of the individual positions lies in the telescoped array in the ± 0.5 μm to ± 2 μm range.
In order to obtain low tolerances of this sort, the individual bars are kept at a distance
by spacers in the pushed-together position.
[0041] After the individual glass fibers have been transferred into the specified
positions through the fine-meshed matrix and there temporarily aligned, the glass fiber
ends present in an ordered matrix are affixed in the aligned position, for example by
means of a casting material or potting material. Preferably, the fiber ends are coated
with a plastic/adhesive that is subsequently hardened. In this way, a fixed alignment
of the fiber ends in the desired position is attained.
[0042] Subsequently, the cable end produced in this way can be ground and
polished true so that a planar fiber array is obtained. The rough positioning of the
glass fiber ends can be assisted by moving or vibrating the alignment apparatus and/or
the glass fiber ends.
[0043] A preferred configuration of the flexible alignment device of the
invention which is configured as a matrix is represented in Figures 2 A and 2B.
[0044] The flexible matrix includes a supporting frame 9, a system of cross bars
10, 12 which define a large number of openings 14 in the matrix structure. The
distance between the bars is set such that the insertion of a second fiber through any of
the openings is prevented. The diameter of the individual bars corresponds to the
standard distance between the individual glass fibers in the array to be produced
whereby the bar widths are advantageously smaller than the diameters of the glass
fiber ends.
[0045] As represented in Figure 2A, the bars in this first position form a
relatively coarse-meshed net.
[0046] After the individual fibers have been transferred into the large openings
14 of the coarse-meshed net of the flexible matrix, the rods are moved in the direction
of arrow 16 to stop 18 and spaced apart by a set distance by spacers 19. In the fine
meshed net represented in Figure 2B, the individual glass fiber ends 1 are tightly
packed into a matrix and are spaced apart by a distance which corresponds to the bar
width of the individual bars 10, 12, whereby the diameter of the bars is preferably
smaller than the diameter of an individual glass fiber end.
[0047] In Figure 3, a glass fiber cable 100 which was manufactured according
to the method of the invention is represented. The glass fiber cable 100 includes a
large number of glass fiber ends 1 which are arranged in an array. The size of the
array can, for example, be 10 x 10 or 35 x 35, or any other desired size, and can also
be a non-square, rectilinear glass fiber array with, for example, 16 x 32 glass fibers.
The distance d of the individual fiber cores to one another comes to 125 μm in the
present embodiment, the tolerance in the placement deviation is ± 3 μm. The
individual glass fibers are preferably formed of a glass fiber core with a diameter in
the 50μm range, a cladding, which surrounds the glass fiber core, as well as a
protective coating. One preferred glass fiber with protective layer has a diameter of
approximately 110 to 120 μm. Of course, arrays with other arrangements or with
glass fibers with a different dimensioning are also possible without deviating from the
invention.
[0048] Preferably, a casing 110 surrounds the large number of fibers.
[0049] Quartz, other types of glass or a plastic material can be used as glass
fiber material. The glass fiber surface includes an acrylate coating. Multi-modal as
well as single mode fibers can be used.
[0050] A complete glass fiber cable results when a plug connection is placed at
both ends of the array of glass fibers.
[0051 ] With the method of the invention, it is possible for the first time to
manufacture a glass fiber cable which includes a multi-dimensional matrix of
individual glass, quartz or plastic fibers in an ordered arrangement. The advantage of
the method in particular lies in that it is herewith possible for the first time to create a
glass, quartz or plastic fiber array where the distance between the individual glass,
quartz or plastic fibers is smaller than the diameter of the individual fibers, whereby
the positioning within the array has tolerances in the range of ± 2 - ± 0.5 μm.