U.S. patent application number 09/865047 was filed with the patent office on 2002-08-22 for method of grinding optical fiber connector.
Invention is credited to Iijima, Takashi, Ishii, Akio, Narita, Takehiko, Suematsu, Katsuki, Yamada, Kunio.
Application Number | 20020115386 09/865047 |
Document ID | / |
Family ID | 18659789 |
Filed Date | 2002-08-22 |
United States Patent
Application |
20020115386 |
Kind Code |
A1 |
Iijima, Takashi ; et
al. |
August 22, 2002 |
Method of grinding optical fiber connector
Abstract
The present invention provides a method of grinding an optical
fiber connector such that the end faces of optical fibers to be
held by the optical fiber connector extends externally from the end
face of said optical fiber connector, comprising a step of grinding
the end faces of the optical fibers while applying a grinding
liquid containing a grinding material and alcohol onto a grinding
sheet.
Inventors: |
Iijima, Takashi; (Tokyo,
JP) ; Ishii, Akio; (Tokyo, JP) ; Suematsu,
Katsuki; (Tokyo, JP) ; Yamada, Kunio; (Chiba,
JP) ; Narita, Takehiko; (Chiba, JP) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
620 NEWPORT CENTER DRIVE
SIXTEENTH FLOOR
NEWPORT BEACH
CA
92660
US
|
Family ID: |
18659789 |
Appl. No.: |
09/865047 |
Filed: |
May 24, 2001 |
Current U.S.
Class: |
451/41 ;
451/59 |
Current CPC
Class: |
B24B 19/226 20130101;
B24B 1/00 20130101 |
Class at
Publication: |
451/41 ;
451/59 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2000 |
JP |
2000-154735 |
Claims
1. A method of grinding an optical fiber connector such that the
end faces of optical fibers to be held by the optical fiber
connector extends externally from the end face of said optical
fiber connector, comprising a step of grinding the end faces of the
optical fibers while applying a grinding liquid containing a
grinding material and alcohol onto a grinding sheet.
2. The method of grinding an optical fiber connector as defined in
claim 1 wherein said grinding liquid is prepared by mixing alumina
powder with polyalcohol.
3. The method of grinding an optical fiber connector as defined in
claim 1 wherein said grinding liquid is prepared by mixing alumina
powder with monoethylene glycol.
4. The method of grinding an optical fiber connector as defined in
claim 3 wherein said grinding liquid is prepared by mixing one part
of alumina powder with 1-2 parts of monoethylene glycol by weight.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method of grinding an
optical fiber connector.
[0002] In recent years, an integral resin-molded MT connector has
been used as a multi-core connector. As shown in FIG. 4(A), the MT
connector 1 has a plastic ferrule body 2 formed with an opening 2a
at one end and a rubber boot portion 3 externally extending from
the distal end of the ferrule body 2.
[0003] The distal end of the body 2 is also provided with a flange
2b. The flange 2b includes an aperture 2f formed therethrough. The
aperture 2f communicates with the opening 2a. The opening 2a also
communicates with a plurality of through-holes 2c which are formed
through the body 2 and opened at the end face 2e thereof. The body
2 includes a pair of pin receiving apertures 2d formed therein at
the opposite sides (see FIG. 4(B)).
[0004] Where the MT connector 1 is used to hold optical fibers 4,
the tip end of an optical fiber tape 5 is first stripped off to
expose the optical multi-core fibers 4 housed within the optical
fiber tape 5.
[0005] The exposed tip ends of the optical fibers 4 are then
inserted into the opening 2a through the aperture 2f. After the
exposed optical fibers 4 have been passed through the through-holes
2c, their tip ends extend externally from the end face 2e of the
body 2.
[0006] Subsequently, an adhesive 6 (e.g., thermosetting adhesive)
is injected into the opening 2a to cover the optical fibers 4
extending externally from the end face 2e (see FIG. 4(C)).
[0007] After the adhesive 6 has thermally been hardened, the end
face 2e of the body 2 is ground to remove the externally extending
optical fiber tips 4 and adhesive 6. Thus, the optical fibers 4 can
be held within the MT connector 1.
[0008] As shown in FIGS. 5(A), (B) and FIG. 6(A), a pair of such MT
connectors 1a and 1b respectively holding the optical fibers 4 are
connected to each other through a pair of connection pins 7. More
particularly, the connection pins 7 are first inserted into the pin
receiving apertures 2d in one of the MT connectors 1a and then
inserted into the pin receiving apertures 2d in the other MT
connector 1b.
[0009] Finally, as shown in FIG. 6(B), a fitting clip 8 is mounted
around the pair of connected MT connectors 1a and 1b to hold them
in the abutting relationship. This completes the connection of
optical fibers. Alternatively, the MT connectors 1a and 1b may
fixedly be mounted in housings which are in turn inserted into a
connector adaptor to hold the MT connectors 1a and 1b in the
abutting relationship.
[0010] In the prior art, the end faces of the MT connector land
optical fibers 4 have been ground flat. In such a case, however, an
index matching agent (or matching oil) must additionally be applied
onto the end face 2e to avoid any connection loss and to ensure a
desired return loss.
[0011] To avoid such an additional work, there has been proposed a
technique known as PC (Physical Contact) connection in which the
end face 2e of the body 2 is ground such that the end faces of the
optical fibers 4 externally extend from the end face 2e of the body
2 by few microns. On connection, the optical fibers 4 in the MT
connectors are brought into contact with one another. As a result,
the connection property of low loss and reflection can be realized
without use of any index matching agent. The grinding process
herein was carried out while applying a mixture of alumina power
and distilled water onto a grinding sheet.
[0012] In such a prior art grinding process, the cores of the
optical fibers 4 will be ground more than the clad portions to
create recesses at the cores of the optical fibers 4. When the
optical connecters are connected to each other, the recesses create
gaps between the cores. This may adversely affect the light
transmission and return loss to reduce the reliability in the
optical connectors.
SUMMARY OF THE INVENTION
[0013] The present invention provides a method of grinding an
optical fiber connector such that the end faces of optical fibers
to be held by the optical fiber connector extends externally from
the end face of said optical fiber connector, comprising a step of
grinding the end faces of the optical fibers while applying a
grinding liquid containing a grinding material and alcohol onto a
grinding sheet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIGS. 1(A) to (C) are plan views illustrating a process of
grinding an optical fiber connector according to one embodiment of
the present invention.
[0015] FIG. 2 is a side view showing a grinding sheet and grinding
liquid which are used in the process of grinding an optical fiber
connector according to one embodiment of the present invention.
[0016] FIG. 3(A) is a view illustrating a recess created at an
optical fiber core when it is ground according to the prior art
grinding process while FIG. 3(B) a view illustrating a recess
created at an optical fiber core when it is ground according to the
present invention.
[0017] FIG. 4(A) is a plan view of an MT connector; FIG. 4(B) is a
front view of the same; and FIG. 4(C) is a plan view illustrating
optical fibers externally extending from the end face of the
connector body and covered with an adhesive.
[0018] FIG. 5(A) is a plan view showing a pair of MT connectors
prior to connection while FIG. 5(B) is a similar plan view showing
the MT connectors after connected to each other.
[0019] FIG. 6(A) is a side view showing the pair of MT connectors
prior to connection while FIG. 6(B) is a similar side view showing
the MT connector pair held by a fitting clip in the abutting
state.
DETAILED DESCRIPTION
[0020] The present invention will now be described by way of
example with reference to the drawings. Parts similar to those of
the prior art are denoted by similar reference numerals and will
not further be described.
[0021] In one embodiment of the present invention, the adhesive 6
(e.g., thermosetting adhesive) is injected into the opening 2a to
cover the optical fibers 4 externally extending from the end face
2e of the body (see FIG. 4(C)). After the adhesive 6 has thermally
been hardened, the adhesive 6 deposited on the end face 2e of the
body 2 is ground off (see FIG. 1(A)). This adhesive removing step
is continued for about 60 seconds.
[0022] The flatting is carried out to improve the flatness and to
reduce scratches on the end face 2e of the body (see FIG. 1(B)).
This flatting step is continued for about 30 seconds. The grinding
step is then performed such that the end faces of the optical
fibers 4 extend externally from the end face 2e of the body 2 (see
FIG. 1(C)). This grinding step is continued for about 90
seconds.
[0023] Finally, the finishing step is made to remove small
scratches on the end faces of the optical fibers 4. This finishing
step is continued for about 5 seconds.
[0024] The aforementioned grinding step is carried out by mounting
a grinding sheet 11 of about one mm thick on a grinder 9 of a
grinding machine (not shown) as shown in FIG. 2 and rotating the
grinder 9 to grind the end faces of the body and optical fibers
while applying a grinding liquid 12 consisting of a mixture of
grinding material and alcohol onto the grinding sheet 11.
[0025] The grinding sheet 11 may be in the form of diamond sheet,
for example. The grinding liquid 12 may be a liquid prepared by
mixing alumina power with monoethylene glycol in a ratio of 1:2. In
the prior art, a grinding liquid prepared by mixing aluminum powder
with distilled water was used. In such a case, the finished fiber
faces were inferior. Thus, the prior art must grind the optical
fibers by using a grinding liquid prepared by mixing ceric oxide
with distilled water in the finishing step. Nevertheless, it could
not avoided that the recesses 4a were created at the cores of the
optical fibers 4 merely by performing the grinding step using that
grinding liquid.
[0026] On the contrary, the finished optical fiber end faces can be
improved when the grinding liquid consisting of alumina powder and
monoethylene glycol is used as in this embodiment. In the finishing
step, the creation of recesses 4a in the optical fibers can be
reduced without use of the grinding liquid prepared by mixing ceric
oxide with distilled water.
[0027] FIG. 3 shows experimental results which were obtained by the
inventors. FIGS. 3(A) and (B) show measurements obtained by using a
surface roughness measuring machine when the later was used to
measure the surface roughness in the ground MT connector 1. FIG.
3(A) shows the result from the prior art while FIG. 3(B) shows the
result from the grinding process according to this embodiment.
[0028] Referring to FIG. 3(A), the prior art created a recess 4a
having its depth of about 0.1 .mu.m or less at the core of the
optical fiber 4.
[0029] On the other hand, the grinding process according to this
embodiment will create no recess at the core of the optical fiber
4, as shown in FIG. 3(B).
[0030] As a result, the Fresnel reflection of this embodiment
created when the ground MT connectors are connected to each other
in the abutting relationship as shown in FIG. 6 was smaller than
that of the prior art.
[0031] Experimental estimation of the grinding liquid carried out
by the inventors will be described below.
[0032] As shown in Table 1, the fiber end recess, fiber extension
and operability were estimated relating to a grinding liquid (or
grinding material) prepared by mixing one part of alumina powder
with 1-3 parts of monoethylene glycol by weight and another
grinding liquid (or grinding material) prepared by mixing one part
of alumina powder with 1-3 parts of distilled water by weight.
1 TABLE 1 For One Part of Alumina Powder by Weight Grinding
Monoethylene Glycol Distilled Water Material 1 2 3 1 2 3 Fiber None
None None Yes Yes Yes recess Fiber Good Good Bad Good Good Bad
Extension (None) (None) Operability Slightly Good Good Good Good
Good Bad
[0033] As will be apparent from Table 1, the grinding liquid
prepared by mixing one part of alumina powder with 1-2 parts of
monoethylene glycol by weight does not form any fiber recess and
provides good fiber extension.
[0034] The inventors also performed experiments relating to the
concentration of the grinding liquid. Usually, the mixed liquid has
been prepared by mixing one part of alumina powder with two parts
of monoethylene glycol by weight. The experiments were carried out
by using grinding liquids prepared by mixing monoethylene glycol
with distilled water in various ratios shown in Table 2.
2 TABLE 2 Monoethylene Alumina Powder Glycol Distilled Water Type 1
10 g 15 g 5 g Type 2 10 g 10 g 10 g Type 3 10 g 5 g 15 g Normal 10
g 20 g 0 g
[0035] Table 3 shows the results from the above experiments. As
will be apparent from Table 3, no core was formed and the finished
end faces were good, even though the concentration was changed.
However, it was found that as the concentration of the monoethylene
glycol decreased, the fiber extension also decreased.
3 TABLE 3 Extension Core Recess Finished End Face Type 1 2.95 .mu.m
None Good Type 2 2.83 .mu.m None Good Type 3 2.6 .mu.m None
Good
[0036] The present invention is not limited to the above
embodiment, but may be modified or changed into various forms
without departing from the scope of the invention as claimed in the
appending claims. For example, the present invention may be applied
to any connector other than the MT connector.
[0037] According to this embodiment of the present invention, the
creation of recess in the cores of the optical fibers can be
reduced to provide good extension of the optical fibers from the
end face of the ferrule body, since the optical fibers are ground
by using the grinding sheet while applying the grounding liquid
prepared by mixing a grinding material with alcohol. As a result,
the return loss can be improved to increase the reliability in the
optical fiber connector.
* * * * *