U.S. patent application number 11/206504 was filed with the patent office on 2005-12-29 for process for cutting an optical fiber.
This patent application is currently assigned to Tyco Electronics Corporation. Invention is credited to Maria Hultermans, Antonius Petrus Cornelis, Stroobach, Pieter, Vergeest, Henricus Jozef.
Application Number | 20050284852 11/206504 |
Document ID | / |
Family ID | 29273331 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050284852 |
Kind Code |
A1 |
Vergeest, Henricus Jozef ;
et al. |
December 29, 2005 |
Process for cutting an optical fiber
Abstract
A process for cutting or splitting at least one optical fiber at
a predetermined angle, wherein the fiber is introduced into a
holding and positioning device and is cut by a pulsed laser
beam.
Inventors: |
Vergeest, Henricus Jozef;
(Heterogenbosch, NL) ; Maria Hultermans, Antonius Petrus
Cornelis; (Tilburg, NL) ; Stroobach, Pieter;
(Eindhoven, NL) |
Correspondence
Address: |
TYCO ELECTRONICS CORPORATION
4550 NEW LINDEN HILL ROAD, SUITE 450
WILMINGTON
DE
19808
US
|
Assignee: |
Tyco Electronics
Corporation
Middletown
PA
|
Family ID: |
29273331 |
Appl. No.: |
11/206504 |
Filed: |
August 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11206504 |
Aug 18, 2005 |
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09880698 |
Jun 12, 2001 |
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6963687 |
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09880698 |
Jun 12, 2001 |
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09395352 |
Sep 14, 1999 |
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6246026 |
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60229787 |
Sep 1, 2000 |
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Current U.S.
Class: |
219/121.67 ;
219/68; 385/123; 65/392 |
Current CPC
Class: |
B23K 26/0648 20130101;
G02B 6/25 20130101; B23K 26/0665 20130101; B23K 26/38 20130101;
B23K 26/0624 20151001; G02B 6/4249 20130101; B23K 2103/50 20180801;
G02B 6/30 20130101; B23K 26/064 20151001; G02B 6/4202 20130101;
B23K 26/40 20130101 |
Class at
Publication: |
219/121.67 ;
385/123; 065/392; 219/068 |
International
Class: |
B23K 026/16; C03B
037/016 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 1998 |
EP |
98117698.5 |
Claims
We claim:
1. A process for cutting at least one optical fiber, the process
comprising the steps of: introducing a glass fiber into a holding
and positioning device; actuating a laser device to deliver a beam
having a power suitable for sublimating glass; and effecting the
relative movement of said beam across said glass fiber along a path
comprising two predetermined angles, thereby sublimating glass and
cutting said glass fiber along said path to shape a wedge on the
end face of the fiber.
2. A process for cutting at least one optical fiber, the process
comprising the steps of: introducing a glass fiber into a holding
and positioning device; actuating a laser device to deliver a beam
having a power suitable for sublimating glass; and effecting the
relative movement of said beam across said glass fiber along a path
having a predetermined angle, thereby sublimating glass and cutting
said glass fiber along said path, said predetermined angle being
repeatable within less than +/-0.5.degree. at the core region.
3. The process according to claim 1, wherein said beam is a
continuation wave.
4. The process according to claim 1, wherein said beam is
pulsed.
5. The process according to claim 1, wherein the laser is a
CO.sub.2 laser.
6. A fiber prepared in accordance with the process of claim 1.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of prior application Ser.
No. 09/880,698, filed on Jun. 12, 2001, which is a continuation in
part of application Ser. No. 09/395,352, filed on Sep. 14, 1999,
and claims priority to provisional application No. 60/229,787 filed
on Sep. 1, 2000. These applications are incorporated herein by
reference in their entirety.
FIELD OF THE INVENTION
[0002] The invention relates to cutting one or more fibers to form
angled or shaped end faces that require no polishing.
BACKGROUND OF THE INVENTION
[0003] Optical fibers made of glass are often used in optical
transmission systems and other optical systems. The machining of
the end face of these fibers plays a crucial role during the use of
these monomode or multimode fibers. It is important that the end
faces have a particularly uniform surface so that the transition
from one fiber end to another or to an active element can be
carried out with damping values which are as low as possible. It is
also important that the end faces of the fibers can be produced at
predetermined angles and that these angles are reliable and
reproducible.
[0004] Various mechanical processes are currently known for
severing optical fibers. With these processes, the fiber is
typically fixed in a holding device consisting of two holders which
are then mutually offset, for example, so that the correct angle is
ensured during the cutting operation (see, e.g., EP 351,225.) To
effect the cut, a tradition cleaving mechanism such as a diamond
cutter is used. It is also known to twist the fiber or begin to cut
and then break the fibers along the partial cut. After the fiber is
cut, its end face is then polished to minimize optical losses.
[0005] The mechanical approach of cleaving and polishing a fiber
has a number of significant shortcomings. For example, the multiple
steps required makes this approach time-consuming, and, thus,
expensive. The approach of mechanically cleaving and polishing a
fiber also tends to be limited in flexibility. For example, ribbon
cable can be cut only under limited conditions. Furthermore, the
angle of the end face of a fiber is generally limited to less than
15.degree. due to the excessive forces the polishing pad imparts to
the fiber as the angle increases. As used herein, the phrases
"angle of the end face" and "end face angle" refer to the angle
from a perpendicular of the optical axis of the fiber. As the end
face angle increases, the axial force component of the pad on the
fiber increases. Glass fiber tends to lack axial strength. At some
point, the axial force component, in combination with the torsional
force component, causes the fiber tip to fracture. Although this
point various depending upon the polishing technique, the end face
angle is generally below 15.degree..
[0006] Therefore, there is a need for preparing the end face of a
glass fiber which is inexpensive, versatile, and not limited to
certain end face geometries. The present invention fulfills this
need among others.
SUMMARY OF THE INVENTION
[0007] The present invention provides an approach for preparing the
end face of a fiber which avoids the shortcomings of the prior art
by using a laser to cut and polish the end face simultaneously.
According to the present invention, the fiber is held in a holding
and positioning device and the fiber is then cut or machined by
means of a laser beam moving relative to the fiber. As a result, a
fiber end face can be prepared accurately with a predetermined
angle or shape and with surface uniformity such that additional
machining of the fiber end face is unnecessary.
[0008] For example, in a simple configuration, the laser cuts a
straight path across the fiber to form a planar end face. The
planar end face may be normal to the axis of the fiber, or, in a
preferred embodiment, it may be angled to the axis such that the
end face of the fiber serves to change the direction of the light
exiting or entering the fiber. With respect to this preferred
embodiment, since there is no polishing required, the end face may
be cut at an angle greater than 15.degree.. It has been found that
an end face at such an angle, preferably about 45.degree., may be
used to optically couple the fiber to a device which is not along
the fiber's optical path due to its ability to alter the direction
of light. Such a light bending technique may be preferable in many
optical subassemblies, including, for example, a subassembly
comprising a ribbon cable optically coupled to an array of VCSELs
in which the vertical operative axes of the VCSELs are
perpendicular to the optical axes of the fibers of the ribbon
cable.
[0009] Laser cleaving also provides for complex cuts and end face
whereas former mechanical systems were relegated to just straight
cuts. Since the movement of a laser across the fiber is not limited
to simple, straight paths and since no polishing is required, any
end geometry is possible with the present invention. For example,
the fiber end face may be multifaceted or curved to enhance the
optical coupling performance of the fiber. A preferred end face
shape includes a wedge shape formed by two opposing cuts. In
practice, the wedge shaped will tend to be blunted due to surface
tension of the softened fiber during cutting. The blunted wedge
shape therefore acts a cylinder-type lens at the fiber end. Such a
configuration is well suited for optically coupling the fiber with
a laser having an elliptical beam.
[0010] Aside from just complex end face geometries, the present
invention also provides for the end shaping of individual fibers in
a ribbon cable. In one particular preferred embodiment, the laser
is used to cut each fiber of a ribbon cable at an angle other than
perpendicular to the optical axis, thus, achieving a saw tooth
configuration. In another preferred embodiment, the fibers of a
ribbon cable which is to be optically coupled to a waveguide or
other device are configured as they would be in the device, for
example, fanned out, and then each is laser cut to the desired end
face angle. Thus, a complex arrangement, in which each fiber of the
ribbon cable must be cut at a different angle and/or to a different
length due to the fibers fanning out, is made easy.
[0011] Aside from the flexibility offered by the approach of the
present invention in preparing fibers of any desired end face
geometry, the laser's sublimatation of the glass, rather than a
mechanical cut, offers a number of advantages and distinctions over
the prior art. For example, ablation of the glass, as opposed to
mechanical cleaving, provides for a smooth end face which generally
requires little if any subsequent polishing. Furthermore, a laser
cut end face tends to have rounded edges rather than sharp edges.
This rounding occurs because the fiber material becomes somewhat
molten in the vicinity adjacent the cut, and the surface tension of
the glass pulls across the edge, thereby causing the edge to
flatten or become rounded. On the other hand, the end face of a
polished fiber has sharp edges since the fiber does not become
fluid during the polishing step to the extent that the surface
tension of the fiber material has any significant effect. Such
differences in end face geometry are significant. For example, the
rounded edges formed by laser cleaving are better suited for
V-groove alignment applications since the rounded edges glide along
the V-groove rather than schriving it as a sharp edge might and
potentially creating debris in the optical path.
[0012] The present invention is also able to prepare an end face
with unprecedented accuracy and precession. For example, whereas
former mechanical systems have typical angle tolerances of +/-0.5
.mu.m, angle tolerances of less than +/-0.2 .mu.m can be achieved
with the process according to the invention. Additionally, the
present invention offers a high degree of control over the position
of the cleaved end face relative to a reference point. For example,
it has been observed that a tolerance of less than +/-10 .mu.m is
achievable. Furthermore, it has been observed that the laser can
cleave within 1 mm of the fiber coating with suitable results.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic view of an optical waveguide with a
coordinate system and a laser beam;
[0014] FIG. 2 is a cross section through one end of an optical
waveguide;
[0015] FIG. 3 is a schematic view of optical waveguides of a ribbon
cable fastened in a holding and positioning device;
[0016] FIG. 4 is a schematic view of a wedged-shaped end of a fiber
prepared using the laser cleaving of the present invention;
[0017] FIG. 5 is a photograph showing fibers having different end
face angles;
[0018] FIG. 6 shows a schematic of an optical subassembly
comprising fibers of a ribbon cable optically coupled to an array
of VCSELS;
[0019] FIG. 7 shows a schematic of a planar component comprising
fibers of a ribbon cable optically coupled to a planar waveguide;
and
[0020] FIG. 8 shows a silicon wafer board having V-grooves for
aligning fibers of a ribbon cable with an active component mounted
thereon.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0021] Referring to FIG. 1, a laser L.sub.A from which a laser beam
L.sub.S issues is initially required for carrying out the process
of cutting a fiber 3. The optical fiber 3 is a glass fiber, for
example a monomode or multimode fiber. As shown in FIG. 2, the
fiber 3 consists of a fiber core 4 and a fiber sheath 5 so that the
light is guided substantially in the fiber core 4.
[0022] In general, any laser with a wavelength between 0.1 and 1.5
.mu.m and 8.5 .mu.m to 10 .mu.m can be used for producing the beam
for cleaving the fibers. Suitable lasers include, for example,
CO.sub.2 and excimer lasers, although a CO.sub.2 laser is
preferred. CO.sub.2 lasers have proven particularly advantageous
due to the high speed at which they can operate and their resultant
cost effectiveness. The fiber material is removed by ablation by
the CO.sub.2 laser during the cutting process, such that, rather
than melting, the glass is sublimated.
[0023] Balancing the objective of delivery high energy to fiber to
ablate the glass is the need to minimize the energy absorbed by the
glass surrounding the cut so as to minimize melting. For this
reason, the CO.sub.2 laser is operated preferably in a pulsed mode
for cutting the fiber, although it may be preferable for other
types of lasers, or even the CO.sub.2 laser, to be operated in a
continuous wave mode. (For example, if time the laser impinges the
fiber is decreased, i.e., the laser cuts across the fiber more
quickly, it may be desirable to operate the laser in continuous
wave mode.) In the pulse mode, the laser transmits short
high-energy pulses of laser light so that the material of the fiber
is sublimated. The pulses are very short and have very steep edges,
thus, the maximum pulse energy is achieved very rapidly. For
example, suitable results have been achieved in which the peak
power of the pulse is between about 0.1 and about 1000 watts and
the pulse length is greater than about 50 fs. Very good results are
achieved with a CO.sub.2 laser (wavelength 10.6 .mu.m) having a
pulse length of 35 .mu.s and a peak power of 600 watts.
[0024] The fiber 3 is arranged in a holding and positioning device
and is positionable relative to the laser L.sub.A. Preferably, the
device is configured to move the fiber at one or more predetermined
angles relative to the laser beam, although it is within the scope
of the present invention to move the laser beam relative to the
fiber. In one embodiment, the fiber may be oriented along the axis
a.sub.Y and then be moved along the axis X relative to the laser
beam L.sub.S using microtranslators on the holding and positioning
device. However, it is also possible for microtranslators of the
holding and positioning device to move the fiber 3 along the axis
a.sub.X or any other angle or combination of angles and curves
relative to the laser beam.
[0025] The laser beam L.sub.S is concentrated by a lens 1. The
laser beam L.sub.S, once concentrated in this way, impinges on the
optical fiber 3. As shown in FIG. 2, a surface 6 of the fiber 3 is
produced at an inclination angle to the fiber axis. The angle of
inclination can be accurately reproducible. Furthermore, a very
accurate and high quality surface of the fiber is achieved by
"laser cutting," so additional machining of the fiber surface after
cutting, as is normal with mechanical cutting processes, is no
longer necessary. In other words, the fiber end face 6 is finished
sufficiently after cutting with the laser.
[0026] As shown in FIG. 3, with the process according to the
invention, it is possible to cut not only an individual fiber and
adequately finish the end surface at the same time, but also a
bundle of fibers 3 oriented parallel to one another (for example, a
ribbon cable) simultaneously with the same surface qualities. For
this purpose, the fibers 3 that make up a bundle are introduced
into a positioning device 7. The positioning device 7 ensures that
the fibers 3 are arranged parallel to one another. The longitudinal
axis of the fibers 3 coincides, for example, with the X-axis of a
coordinate system. The positioning device 7 can now be driven along
the direction of the Y-axis in a manner that ensures that the
fibers 3 remain in parallel orientation.
[0027] The laser beam L.sub.S, which in this embodiment is inclined
by an angle .alpha. to the Z-axis, is concentrated onto the fibers
3 by means of a lens 1 and operated in a mode with short
high-energy pulses described above. The fibers 3 pass through the
laser beam L.sub.S and are thus cut and the end faces
simultaneously finished. Advantageously, this process ensures that
all fibers of the ribbon cable are cut at the same angle with an
equally high end face quality.
[0028] As mentioned before, the present invention is able to
prepare an end face of a fiber with any desired geometry. Referring
to FIG. 5a-c, a fiber 51 is shown with different end faces 53, 54,
and 55 of 0.degree., 8.degree. and 45.degree. respectively.
Noteworthy is the rounded edge 52 of fiber 1 which is a distinction
over mechanically cleaved and polished fibers. Furthermore, as
shown in FIG. 4, laser cleaving of the present invention can be
used to form a wedged-shaped fiber end 41. This wedge shape was
formed by passing the fiber through the laser beam at different
angles. The wedge shaped fiber end 41 is slightly blunted
presumably due to surface tension of the softened fiber during
laser ablation. The blunted wedge shape therefore presents a
cylinder-type lens 42 at the fiber end. Such a configuration is
well suited for optically coupling the fiber with pump-type lasers
or other devices which emit or receive an elliptical beam of
light.
[0029] Referring to FIG. 6, an optical subassembly 60 is shown
comprising a plurality of fibers 61 arranged in a ribbon cable 65
and optically coupled to VCSELs 63, although the same configuration
may be used to optically couple fibers to any device. The optical
coupling is achieved by using the reflective properties of the end
face 62. As shown, the end face angle is about 45.degree. which
reflects the light between the operative axis 64 of the VCSEL 63
and the optical axis 66 of the fiber 61 at about a right angle. The
embodiment shown in FIG. 6 illustrates the versatility of the
present invention and its ability to prepare the end faces of a
plurality of fiber in a ribbon cable to couple with an array of
VCSELS.
[0030] Referring to FIG. 7, a planar optic component 70 is shown
comprising waveguide 71 integrated with fibers 72 having end faces
74 prepared according to the present invention. The fibers 72 are
part of a ribbon cable 73 and yet have individually angled end
faces 74 which could not have been prepared by simply cutting
across the ribbon using a traditional mechanical cutting
instrument. In a preferred embodiment, the end faces 74 are
prepared by fanning the fibers out as they would be configured in
the planar optical component, and then cleaving each fiber to a
desired angle. This way, the specific lengths of the fibers--i.e.,
the long lengths of the exterior fibers 72a relative to the
interior fibers 72b--and end face angles are addressed in a single
operation.
[0031] Referring to FIG. 8. a silicon wafer platform 80 is shown
comprising a substrate 85 having a number of V-grooves 81 and at
least one active component 82 mounted thereon. A plurality of
fibers 83 of a ribbon cable are aligned in the V-grooves 81 to
optically couple with the component 82. Aside from facilitating
individually angled fibers as mentioned above, the present
invention provides for an improved end face for aligning in
V-groove. Specifically, laser cleaving results in rounded edges
along the perimeter of the fiber. The rounded edges have a tendency
to glide along the V-groove as compared to sharp-edged end faces
produced by mechanical fiber cleaving which tend to schrive the
V-groove surface. This schriving kicks up or creates debris which
may diminish the device's optical performance.
* * * * *