U.S. patent application number 10/602477 was filed with the patent office on 2004-02-12 for polishing pad for polishing optical fiber connectors.
This patent application is currently assigned to Nihon Microcoating Co., Ltd.. Invention is credited to Baba, Tetsuya, Bang, Vuong Van, Tamura, Jun.
Application Number | 20040028346 10/602477 |
Document ID | / |
Family ID | 25472725 |
Filed Date | 2004-02-12 |
United States Patent
Application |
20040028346 |
Kind Code |
A1 |
Baba, Tetsuya ; et
al. |
February 12, 2004 |
Polishing pad for polishing optical fiber connectors
Abstract
Optical fiber connectors each with a plurality of optical fibers
protruding from the front surface of a main body by improved and
uniform distances are produced by being subjected to an etching
step in which a textile pad free of abrading particles and a slurry
containing abrading particles of a relatively larger size are used
and thereafter to a final fine polishing step in which a polishing
pad with a porous and compressive sponge-like material without
affixed abrading particles and a slurry of another kind containing
relatively smaller abrading particles are used. The sponge-like
material may be polyurethane and is required to have hardness and
pores with sizes within specified ranges.
Inventors: |
Baba, Tetsuya; (Tachikawa,
JP) ; Tamura, Jun; (Fussa, JP) ; Bang, Vuong
Van; (San Jose, CA) |
Correspondence
Address: |
BEYER WEAVER & THOMAS LLP
P.O. BOX 778
BERKELEY
CA
94704-0778
US
|
Assignee: |
Nihon Microcoating Co.,
Ltd.
|
Family ID: |
25472725 |
Appl. No.: |
10/602477 |
Filed: |
June 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10602477 |
Jun 23, 2003 |
|
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09939198 |
Aug 24, 2001 |
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6632026 |
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Current U.S.
Class: |
385/85 |
Current CPC
Class: |
G02B 6/3885 20130101;
B24B 37/042 20130101; G02B 6/3861 20130101; G02B 6/3863 20130101;
B24B 19/226 20130101 |
Class at
Publication: |
385/85 |
International
Class: |
G02B 006/36 |
Claims
What is claimed is:
1. A method of polishing an optical fiber connector, said method
comprising the steps of: providing an optical fiber connector which
comprises a main body having a front surface, an opposing back
surface, a plurality of throughholes extending therethrough from
said back surface to said front surface, and optical fibers each
extending through a respective one of said throughholes and having
a front end portion exposed at said front surface of said main
body; polishing said front surface of said main body with a textile
pad free of abrading particles affixed thereto and a first slurry,
said textile pad etching said front surface preferentially relative
to said optical fibers such that the front end portions of said
optical fibers protrude beyond the preferentially etched front
surface of said main body; and thereafter polishing said front
portions of said optical fibers with a porous and compressive
sponge-like material without abrading particles affixed thereto and
a second slurry such that said front end portions of said optical
fibers protrude beyond said preferentially etched front surface of
said main body by lengths with variations which are within a
specified value about an average length.
2. The method of claim 1 wherein said average length is over 1
micron.
3. The method of claim 2 wherein said average length is over 3
microns.
4. The method of claim 2 wherein said specified value is 0.5
microns.
5. The method of claim 3 wherein said specified value is 0.5
microns.
6. The method of claim 4 wherein said optical fibers are arranged
linearly through said main body and the maximum difference between
the protruding lengths of a mutually adjacent pair of said optical
fibers is less than 0.2 microns.
7. The method of claim 5 wherein said optical fibers are arranged
linearly through said main body and the maximum difference between
the protruding lengths of a mutually adjacent pair of said optical
fibers is less than 0.2 microns.
8. The method of claim 1 wherein said textile pad comprises nylon
and said first slurry includes abrading particles with average
diameter in the range of 3-5 microns.
9. The method of claim 1 wherein said textile pad comprises nylon
and said first slurry includes abrading particles with average
diameter in the range of 3-5 microns.
10. The method of claim 1 wherein said sponge-like material is
polyurethane with hardness between 20-80 duro, having pores with
sizes between 20-100 microns.
11. The method of claim 8 wherein said sponge-like material is
polyurethane with hardness between 20-80 duro, having pores with
sizes between 20-100 microns.
12. The method of claim 10 wherein said second slurry includes
abrading particles with average diameter in the range of 0.1-2.0
microns.
13. The method of claim 11 wherein said second slurry includes
abrading particles with average diameter in the range of 0.1-2.0
microns.
14. The method of claim 12 wherein front surfaces of said optical
fibers have surface roughness R.sub.a of less than 2 nm after being
polished by said sponge-like material.
15. The method of claim 13 wherein front surfaces of said optical
fibers have surface roughness R.sub.a of less than 2 nm after being
polished by said sponge-like material.
16. A polishing pad comprising a layer of a porous and compressive
sponge-like material and an adhesive tape on which said layer is
attached, said sponge-like material having hardness in the range of
20-80 duro, having pores with sizes in the range of 20-100
microns.
17. The polishing pad of claim 16 wherein said layer has a
thickness in the range of 300-1500 microns.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a method of polishing optical
fiber connectors and a device which is used in such a method. More
particularly, this invention relates to a polishing method as a
part of a production process for connectors each with a plurality
of optical fibers protruding from a front surface of a main body
and a pad which is used in such a polishing process such that the
variations in the length of protrusion can be reduced and the
protruding optical fibers will each have a flatter front
surface.
[0002] Optical fiber connectors of this type have been known, and
it has also been known to polish such optical fiber connectors by
using a fibrous material such as comprising nylon and polyethylene
with abrasive particles attached thereto and without using a
slurry. This method, however, is less than satisfactory for many
reasons such that the process takes too long a time, that the
finished surfaces tend to be scratched and that sufficient
protrusions cannot be obtained. More significantly, such prior art
methods have not been able to sufficiently control the protrusions
of the individual optical fibers such that the variations among the
protrusions of the individual fibers were relatively large and the
tips of the protruding optical fibers were not sufficiently even,
smooth or flat, tending to become thinner near the front end.
SUMMARY OF THE INVENTION
[0003] It is therefore an object of this invention to provide a new
method of polishing optical fiber connectors with a plurality of
optical fibers therethrough such that the optical fibers protrude
from the front surface of a main body by an improved length of 1-3
microns and preferably longer with reduced variations and have
flatter, smoother and more even front surfaces than was possible
with prior art methods.
[0004] It is another object of the invention to provide a polishing
pad with which such improved optical fibers can be produced.
[0005] A method embodying this invention, with which the above and
other objects can be accomplished, may be characterized as
comprising the steps of carrying out a preferential etching step of
the front surface by using a textile pad free of abrading particles
affixed thereto and a slurry containing abrading particles of a
relatively larger size and thereafter polishing front portions of
the optical fibers with a polishing pad with a porous and
compressive sponge-like material without abrading particles affixed
thereto and a slurry of another kind containing relatively smaller
abrading particles. Such a sponge-like material may comprise
polyurethane and is required to have hardness within a specified
range. By a method of this invention with the use of a polishing
pad as described above, optical fiber connectors with a plurality
of fibers can be produced with the optical fibers protruding by
longer distances and more uniformly, and having smoother front
surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a greatly enlarged schematic perspective view of
an optical fiber connector produced by a method embodying this
invention;
[0007] FIG. 2 is a schematic sectional side view of the optical
fiber connector of FIG. 1 at a stage during a course of its
production before epoxy is removed;
[0008] FIG. 3 is a schematic sectional side view of the optical
fiber connector of FIG. 2 after the first two steps of a polishing
method of this invention have been carried out;
[0009] FIG. 4 is a schematic sectional side view of the optical
fiber connector of FIG. 2 after the third step of the polishing
method of this invention has been carried out;
[0010] FIG. 5 is a schematic sectional side view of a polishing pad
used in the fourth step of the polishing method of this invention;
and
[0011] FIG. 6 is a schematic sectional side view of the optical
fiber connector of FIG. 2 after the fourth step of the polishing
method of this invention has been carried out.
DETAILED DESCRIPTION OF THE INVENTION
[0012] FIG. 1 shows schematically an example of optical fiber
connector 10 produced by a method embodying this invention. The
optical fiber connector 10 is characterized as comprising a main
body 15 (say, of a plastic material containing glass particles for
providing desired physical characteristics), having a flat front
surface 20, an oppositely facing back surface 25 and a plurality of
optical fibers 30 which extend through throughholes 22 provided
through the main body 15 from the back surface 25 to the front
surface 20, protruding from the front surface 20 by a specified
length which may be in the range of 1-3 microns or greater and
being secured in the respective throughholes 22 by epoxy (not
shown). Although twelve optical fibers 30 are shown linearly
arranged through the main body 15, neither the number of the
optical fibers 30 nor their arrangement is intended to limit the
scope of this invention. On the other hand, it is to be remembered
that the present invention is particularly useful for connectors
with many more than 2 optical fibers passing through and supported
by a main body.
[0013] FIG. 2 shows the optical fiber connector 10 at one stage
during the course of its production after the optical fibers 30
have each been secured inside respective one of the throughholes 22
by epoxy 35. A method of producing optical fiber connectors as
shown in FIG. 1 from the stage shown in FIG. 2 may be described as
including the following four steps, that is, the steps of removing
the epoxy, rough polishing, preferential removal of the main body
material and a final fine polishing. For carrying out all four of
these steps, use may be suitably made of a polishing machine of a
known kind capable of loading a plurality of target objects to be
polished and provided with a rotary disc and a mechanism for
causing each of these loaded target objects to constantly come into
contact with a new portion of a polishing pad removably attached to
the rotary disc.
[0014] The first two of the four steps referred to above are
carried out in conventional ways and hence will not be described in
detail. The first step of epoxy removal may be carried out, for
example, by using a polishing film with abrading particles of
silicon carbide with diameters about 16 microns on the rotary disc
of such a polisher. The second step of rough polishing may be
carried out, for example, by using a polishing film with abrading
particles of silicon carbide with diameters about 5 microns. After
these first two steps have been carried out, the optical fiber
connector 10 will look as shown in FIG. 3, with the front surface
20 of the main body 15 roughly flat and the front surfaces of the
optical fibers 30 substantially flush with this substantially
flattened front surface 20 of the main body 15.
[0015] The third step is for preferentially etching off the front
surface 20 of the main body 15 relative to the optical fibers 30
such that the optical fibers 30 remain protruding from the front
surface 20, as shown in FIG. 4. For this preferential etching of
the front surface 20 in the third step, use is made of a pad of
textile material such as nylon or polyethylene without any abrading
particles affixed thereonto. For the etching, a slurry containing
abrading particles with average diameter in the range of 1-4
microns in an amount of 20-40% (hereinafter also referred to as
"the first slurry") is used together with the textile pad. The
abrading particles may comprise aluminum oxide or silicon carbide.
The use of such a textile pad and such a slurry can effectively
etch the front surface 20 of the main body 15 without unnecessarily
etching side surfaces of the optical fibers 30. In other words, the
optical fibers 30 do not become pointed towards the tip as they
tend to become by a prior art method of preferential etching.
[0016] The fourth step is for final fine polishing for making the
front surfaces of the protruding optical fibers 30 flatter,
smoother and more even. For this process, use is made of a
polishing pad 50 according to this invention, as shown
schematically in FIG. 5. This polishing pad 50 is characterized as
comprising a layer of sponge-like material 52 with thickness in the
range of 300-1500 microns attached to an adhesive tape 54. The
sponge-like material may be porous polyurethane with hardness in
the range of 20-80 duro, having pores with sizes in the range of
20-100 microns.
[0017] In terms of compressibility and elasticity, it may be
characterized as having compressibility in the range of 5-40% and
elasticity in the range of 30-120%. The compressibility and
elasticity are the values obtained from a sample piece of a
suitable size by measuring its thickness To while compressing it
with an initial load of 80 g, further adding an extra load of 800 g
for 5 minutes and measuring its thickness T.sub.1 afterward,
removing this total load of 880 g and thereafter subjecting it to
the initial load of 80 g for 30 seconds to measure its thickness
T.sub.0' again. The compressibility is calculated as
100(T.sub.0-T.sub.1)/T.sub.0 and the compressive elasticity is
calculated as 100(T.sub.0'-T.sub.1)/(T.sub.0-T.sub.1). The
polishing pad 50 itself does not include any abrading particles.
For the final fine finishing process, use is additionally made of a
slurry of another kind containing abrading particles (such as
cerium oxide, diamond and aluminum oxide particles) with an average
diameter in the range of 0.1-2.0 microns in an amount of about 20%
(hereinafter also referred to as "the second slurry"). The use of
such a pad of a sponge-like material without abrading particles
affixed thereto and a slurry of the aforementioned property can
effectively flatten the front surfaces of the optical fibers 30
left protruding from the front surface 20 of the main body 15, as
shown schematically in FIG. 6. Test experiments carried out by the
present inventors showed that optical fibers connectors with
optical fibers protruding from the main body by an average length
in the range of 1-4 microns could be obtained by a method embodying
this invention, with variations in the length of protrusion less
than 0.5 microns and the difference in the length of protrusion
between mutually adjacent pair of optical fibers less than 0.2
microns.
[0018] The surface roughness of the optical fibers 30 thus polished
was measured by means of an atomic force microscope (produced by
Digital Instrument, Inc). The surface roughness R.sub.a was 1.9 nm
(at scan size 50.times.50 microns). As a comparison test, an
optical fiber connector with only two optical fibers passing
through a main body was polished by a conventional method. The
surface roughness R.sub.a was 5.2 nm (at scan size 50.times.50
microns). This shows clearly that a method according to this
invention can polish a multi-fiber optical fiber connector (even of
a kind with many more than two optical fibers therethrough) such
that the polished optical fibers protrude from the front surface of
the main body by an increased length (more than 1 micron and even
more than 3 microns), that the front surfaces of the protruding
optical fibers have reduced surface roughness and that the front
surface of the main body is left with less visible scratches.
[0019] The invention was described above by way of only one example
and as applied to an optical connector of only one kind, but this
example is not intended to limit the scope of the invention. Many
modifications and variations are possible within the scope of the
invention. For example, the number and arrangement of optical
fibers through a main body of each of the connectors to be polished
do not limit the scope of the invention. No example of polishing
machine was disclosed but any commonly available machine, say, with
a rotary disc, may be used in connection with this invention. The
front surfaces of the optical fibers need not be polished so as to
be perpendicular to the direction of their extension. In other
words, the present invention applies equally well to the polishing
of so-called angled fibers with front surfaces sloped with respect
to the direction of their extension. In summary, all such
modifications and variations that may be apparent to a person
skilled in the art are considered to be within the scope of this
invention.
* * * * *