U.S. patent application number 12/044146 was filed with the patent office on 2009-12-03 for method of polishing end face of multi-fiber optical connector.
Invention is credited to Kunio Yamada.
Application Number | 20090298391 12/044146 |
Document ID | / |
Family ID | 39960401 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090298391 |
Kind Code |
A1 |
Yamada; Kunio |
December 3, 2009 |
METHOD OF POLISHING END FACE OF MULTI-FIBER OPTICAL CONNECTOR
Abstract
To provide a method of polishing an end face of a multi-fiber
optical connector capable of eliminating recesses produced in core
parts of multi-mode optical fibers. A polishing base is prepared,
comprising a soft material having a Shore hardness of less than 30
and a film having a thickness of less than 75 .mu.m, without
including any polishing material, on said soft material, and
further comprising a polishing material on said film. Next, a
multi-fiber optical connector having a plurality of multi-mode
optical fibers is arranged so that the tip of the multi-mode
optical fibers come into contact with the upper surface of the film
with a predetermined pressure. Next, the tip of the multi-mode
optical fibers are polished by moving at least one of the polishing
base and the multi-fiber optical connector while maintaining the
contact between the tip of the multi-mode optical fibers and the
upper surface of the film.
Inventors: |
Yamada; Kunio; (Chiba,
JP) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD, SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
39960401 |
Appl. No.: |
12/044146 |
Filed: |
March 7, 2008 |
Current U.S.
Class: |
451/41 ;
451/59 |
Current CPC
Class: |
G02B 6/25 20130101; B24B
19/226 20130101 |
Class at
Publication: |
451/41 ;
451/59 |
International
Class: |
B24B 1/00 20060101
B24B001/00; B24B 7/20 20060101 B24B007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2007 |
JP |
2007-060908 |
Claims
1. A method of polishing an end face of a multi-fiber optical
connector, the method comprising: a first step of preparing a
polishing base, comprising a soft material having a Shore hardness
of less than 30 and a film having a thickness of less than 75
.mu.m, without including any polishing material, on said soft
material, and further comprising a polishing material on said film;
a second step of arranging a multi-fiber optical connector having a
plurality of multi-mode optical fibers so that the tip ends of the
multi-mode optical fibers come into contact with an upper surface
of the film with a predetermined pressure; and a third step of
polishing the tip ends of the multi-mode optical fibers by moving
at least one of the polishing base and the multi-fiber optical
connector while maintaining the contact between the tip ends of the
multi-mode optical fibers and the upper surface of the film.
2. The method of polishing an end face of a multi-fiber optical
connector according to claim 1, wherein the soft material is
composed of a spongy porous substance.
3. The method of polishing an end face of a multi-fiber optical
connector according to claim 2, wherein at least the upper surface
of the film is made coarse by a surface processing.
4. The method of polishing an end face of a multi-fiber optical
connector according to claim 3, wherein the polishing material is
applied to said coarsened upper surface of the film.
5. The method of polishing an end face of a multi-fiber optical
connector according to claim 4, wherein the soft material is a
sponge pad.
6. The method of polishing an end face of a multi-fiber optical
connector according to claim 5, wherein the soft material has a
thickness of approximately 5 mm.
7. The method of polishing an end face of a multi-fiber optical
connector according to claim 4, wherein the film is a polyethylene
terephthalate film (PET film).
8. The method of polishing an end face of a multi-fiber optical
connector according to claim 7, wherein the PET film has a
thickness of approximately 25 .mu.m.
9. The method of polishing an end face of a multi-fiber optical
connector according to claim 4, wherein the polishing material has
an average grain diameter of 0.5 .mu.m or less.
10. The method of polishing an end face of a multi-fiber optical
connector according to claim 1, wherein the first step comprising:
a step of mounting a soft material having a Shore hardness of less
than 30 on a polishing base of a polishing machine; a step of
mounting a film having a thickness of less than 75 .mu.m without
including any polishing material on the soft material; and a step
of supplying a polishing material on an upper surface of the
film.
11. The method of polishing an end face of a multi-fiber optical
connector according to claim 1, wherein in the third step, the
polishing base moves so that the center axis line of the polishing
base describes a circular locus while keeping a rotation-preventing
attitude.
12. The method of polishing an end face of a multi-fiber optical
connector according to claim 1, wherein in the third step, the
multi-fiber optical connector moves so that the center axis line of
the multi-fiber optical connector describes a circular locus while
keeping a rotation-preventing attitude.
13. The method of polishing an end face of a multi-fiber optical
connector according to claim 1, wherein the end face for connection
of the multi-fiber optical connector is polished into a flat
surface in advance and the tip ends of the multi-mode optical
fibers project by a predetermined length from the end face for
connection.
14. A method of polishing an end face of a multi-fiber optical
connector, the method including: a first step of mounting a sponge
pad having a Shore hardness of less than 30 on a polishing base of
a polishing machine; a second step of mounting a polyethylene
terephthalate film (PET film) having a thickness of less than 75
.mu.m without any polishing material on the sponge pad; a third
step of supplying an polishing material on the upper surface of the
PET film; a fourth step of arranging a multi-fiber optical
connector having a plurality of multi-mode optical fibers so that
the tip ends of the multi-mode optical fibers come into contact
with an upper surface of the film with a predetermined pressure;
and a fifth step of polishing the tip ends of the multi-mode
optical fibers by moving at least one of the polishing base and the
multi-fiber optical connector while maintaining the contact between
the tip ends of the multi-mode optical fibers and the upper surface
of the PET film.
15. The method of polishing an end face of a multi-fiber optical
connector according to claim 14, wherein the sponge pad has a
thickness of approximately 5 mm.
16. The method of polishing an end face of a multi-fiber optical
connector according to claim 14, wherein the PET film has a
thickness of approximately 25 .mu.m.
17. The method of polishing an end face of a multi-fiber optical
connector according to claim 14, wherein the polishing material has
an average grain diameter of approximately 0.5 .mu.m or less.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2007-060908, filed in
Japan on Mar. 9, 2007, and the entire contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of polishing an
end face of a multi-fiber optical connector for polishing an end
face of a plurality of optical fibers fixed on a multi-fiber
optical connector by adhesion, in particular, a multi-mode fiber
(MM fiber).
[0004] 2. Description of the Related Art
[0005] In general, in a multi-fiber optical connector, a plurality
of or many optical fibers are aligned inside a ferrule and fixed
thereon by adhesion. The tip part of the optical fiber projects by
a predetermined length outwardly from the end face for connection
of the ferrule. The identical multi-fiber optical connectors are
arranged so that the end faces for connection of the ferrule face
each other and then the tip parts of the optical fibers are
optically connected. Due to this, high speed transmission of a
large amount of data can be realized.
[0006] Such a multi-fiber optical connector is manufactured, for
example, as follows. First, a plurality of optical fibers are
aligned inside a ferule made of resin and fixed by adhesion. Next,
the end face for connection of the ferrule is polished into a flat
surface (surface polishing step). Subsequently, the end face for
connection of the ferrule is buffed using a fine-grain abrasive.
Due to this, the tip part of the optical fiber projects by a
predetermined length outwardly from the end face for connection of
the ferrule (projection step).
[0007] Conventional methods of polishing an end face used for
manufacturing a multi-fiber optical connector have been disclosed
in, for example, Japanese Patent Application Laid-open Nos.
H10-48467, H8-126951, and 2003-334749.
[0008] However, in the above manufacturing of the multi-fiber
optical connector, in the projection step after the surface
polishing step, the projection length of the optical fiber by which
it projects outwardly from the end face for connection of the
ferrule varies from fiber to fiber. In particular, among the
plurality of optical fibers aligned on the end face for connection
of the ferrule, the optical fibers located on both sides project
less than other optical fibers located at portions other than both
sides.
[0009] The reason for that is as follows. Each optical fiber
located at a portion other than both sides is between adjacent
optical fibers. Because of this, it is unlikely that the optical
fiber is polished so excessively that the projection length of the
optical fiber becomes shorter than the projection length of the
optical fibers on both sides. In contrast to this, one of the
optical fibers located on both sides has only one adjoining optical
fiber on one of the sides. On the other opposite side, there is no
optical fiber but only a resin material constituting the ferrule.
Because of this, it is likely that the optical fibers located on
both sides are polished excessively compared to the optical fiber
located on a portion other than both sides and as a result, the
length of the optical fibers located on both sides is
shortened.
[0010] If such multi-fiber optical connectors are connected
optically, it is unavoidable that the contact force between the
optical fibers located on both sides is weakened.
[0011] In the case of a normal quartz-base optical fiber, the
hardness of the core part is less than that of the clad part.
Because of this, there is a tendency that a recess is likely to be
produced in the tip of the core part by the buffing in the
projection step in the manufacture of a multi-fiber optical
connector.
[0012] When, however, the optical fiber is a single-mode fiber (SM
fiber), it is possible to substantially ignore a recess produced in
the tip of the core part. The single-mode fiber is constituted by a
clad part having a diameter of, for example, about 125 .mu.m and a
core part located substantially in the center of the clad part and
having a diameter of, for example, about 8 .mu.m. As described
above, the diameter of the core part of the single-mode fiber is
very small compared to the diameter of the clad part. Because of
this, in the case of a single-mode fiber, a recess produced in the
core part by buffing in the projection process is very small and
the depth thereof from the tip is very small.
[0013] Because of this, in the case of a single-mode fiber, there
arises no problem of connection loss in the optical connection
between the above-mentioned multi-fiber optical connectors. That
the contact force between optical fibers (SM fibers) is weak does
not cause a gap to be produced between the tips of the optical
fibers (SM fibers). Because of this, it is unlikely that the
connection loss between optical fibers (SM fibers), in particular,
the return loss, is affected substantially by the recess in the
core part.
[0014] In contrast to this, the multi-mode fiber (MM fiber) is
constituted by a clad part having a diameter of, for example, about
125 .mu.m and a core part located substantially in the center of
the clad part and having a diameter of, for example, about 50 .mu.m
or 62.5 .mu.m. As described above, the diameter of the core part of
the multi-mode fiber is by far larger than that of the single-mode
fiber. Because of this, in the case of the multi-mode fiber, the
recess produced in the core part by buffing in the projection
process is by far larger than that in the case of a single-mode
fiber. That is, in the tip of the core part of a multi-mode fiber,
a large and deep recess is produced.
[0015] Because of this, in the case of a multi-mode fiber, there
arises a problem of connection loss in the optical connection
between the multi-fiber optical connectors described above. That
the contact force between optical fibers (MM fibers) is weak causes
a gap to be produced between tips of optical fibers (MM fibers).
Because of this, the connection loss between optical fibers (MM
fibers), in particular, the return loss, increases.
SUMMARY OF THE INVENTION
[0016] In order to solve the above problem, an object of the
present invention is to provide a method of polishing an end face
of a multi-fiber optical connector capable of eliminating recesses
produced in core parts of multi-mode optical fibers.
[0017] To achieve the above object, one aspect of the present
invention provides a method of polishing an end face of a
multi-fiber optical connector, the method comprising:
[0018] a first step of preparing a polishing base, comprising a
soft material having a Shore hardness of less than 30 and a film
having a thickness of less than 75 .mu.m, without including any
polishing material, on said soft material, and further comprising a
polishing material on said film;
[0019] a second step of arranging a multi-fiber optical connector
having a plurality of multi-mode optical fibers so that the tip
ends of the multi-mode optical fibers come into contact with an
upper surface of the film with a predetermined pressure; and
[0020] a third step of polishing the tip ends of the multi-mode
optical fibers by moving at least one of the polishing base and the
multi-fiber optical connector while maintaining the contact between
the tip ends of the multi-mode optical fibers and the upper surface
of the film.
[0021] Preferably, the soft material is composed of a spongy porous
substance.
[0022] Preferably, at least the upper surface of the film is made
coarse by a surface processing.
[0023] Preferably, the polishing material is applied to the
coarsened upper surface of the film.
[0024] Preferably, the soft material is a sponge pad.
[0025] Preferably, the soft material has a thickness of
approximately 5 mm.
[0026] Preferably, the film is a polyethylene terephthalate film
(PET film).
[0027] Preferably, the PET film has a thickness of approximately 25
.mu.m.
[0028] Preferably, the polishing material has an average grain
diameter of 0.5 .mu.m or less.
[0029] Another aspect of the present invention provides a method of
polishing an end face of a multi-fiber optical connector, the
method including:
[0030] a first step of mounting a sponge pad having a Shore
hardness of less than 30 on a polishing base of a polishing
machine;
[0031] a second step of mounting a polyethylene terephthalate film
(PET film) having a thickness of less than 75 .mu.m without any
polishing material on the sponge pad;
[0032] a third step of supplying an polishing material on the upper
surface of the PET film;
[0033] a fourth step of arranging a multi-fiber optical connector
having a plurality of multi-mode optical fibers so that the tip
ends of the multi-mode optical fibers come into contact with an
upper surface of the film with a predetermined pressure; and
[0034] a fifth step of polishing the tip ends of the multi-mode
optical fibers by moving at least one of the polishing base and the
multi-fiber optical connector while maintaining the contact between
the tip ends of the multi-mode optical fibers and the upper surface
of the PET film.
[0035] Preferably, the sponge pad has a thickness of approximately
5 mm.
[0036] Preferably, the PET film has a thickness of approximately 25
.mu.m.
[0037] Preferably, the polishing material has an average grain
diameter of approximately 0.5 .mu.m or less.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[0038] These and other objects and the configuration of this
invention will become clearer from the following description of the
preferred embodiments, read in connection with the accompanying
drawings in which:
[0039] FIG. 1 is a schematic perspective view showing an embodiment
of a multi-fiber optical connector used in a method of polishing an
end face according to the present invention;
[0040] FIG. 2A is a schematic enlarged end face view of a
multi-mode optical fiber used in a multi-fiber optical connector
according to the present invention;
[0041] FIG. 2B is a schematic enlarged sectional view of a
multi-mode optical fiber used in a multi-fiber optical connector
according to the present invention;
[0042] FIG. 3A is a schematic explanatory diagram of relevant parts
showing a state when an adhesive removal step is started, the shape
and dimensions of each part being shown exaggerated for easier
understanding;
[0043] FIG. 3B is a schematic explanatory diagram of relevant parts
showing a state after the adhesive removal step is completed, the
shape and dimensions of each part being shown exaggerated for
easier understanding;
[0044] FIG. 4A is a schematic explanatory diagram of relevant parts
showing a state when a surface polishing step is started, the shape
and dimensions of each part being shown exaggerated for easier
understanding;
[0045] FIG. 4B is a schematic explanatory diagram of relevant parts
showing a state when the surface polishing step is completed, the
shape and dimensions of each part being shown exaggerated for
easier understanding;
[0046] FIG. 5A is a schematic explanatory diagram of relevant parts
showing a state when a projection step is started, the shape and
dimensions of each part being shown exaggerated for easier
understanding;
[0047] FIG. 5B is a schematic explanatory diagram of relevant parts
showing a state when the projection step is completed, the shape
and dimensions of each part being shown exaggerated for easier
understanding;
[0048] FIG. 6 is a schematic enlarged sectional view of a
multi-mode optical fiber after the projection step;
[0049] FIG. 7 is a schematic explanatory diagram of relevant parts
showing a recess elimination step in a core part, the shape and
dimensions of each part being shown exaggerated for easier
understanding; and
[0050] FIG. 8 is a schematic enlarged sectional view of a
multi-mode optical fiber after the recess elimination step in the
core part.
DETAILED DESCRIPTION OF THE INVENTION
[0051] FIG. 1 is a schematic perspective view showing an embodiment
of a multi-fiber optical connector used in a method of polishing an
end face according to the present invention, and FIGS. 2A and 2B
are a schematic enlarged end face view and an enlarged sectional
view of a multi-mode optical fiber used in a multi-fiber optical
connector according to the present invention, respectively.
[0052] As shown in FIG. 1, a multi-fiber optical connector 10 is a
connector of MT (Mechanically Transferable) type, including a
rectangular parallelepiped ferrule 20. A plurality of or many
optical fibers 30 are aligned in the ferrule 20 and fixed by
adhesion. A tip part 35 of the optical fiber projects by a
predetermined length outwardly from an end face 25 for connection
of the ferrule 20.
[0053] The ferrule 20 includes optical fiber insertion holes 21 in
which each of the optical fibers 30 is arranged. The tip of the
optical fiber insertion holes 21 open in the end face 25 for
connection of the ferrule 20.
[0054] In one of the side faces of the ferrule 20, in the upper
side face in FIG. 1, an adhesive injection hole 22 is formed. The
adhesive injection hole 22 is communicated with the optical fiber
insertion holes 21. The optical fibers 30 are arranged in the
optical fiber insertion holes 21 and an adhesive 40 is injected
through the adhesive injection hole 22. Due to this, the optical
fibers 30 are fixed on the ferrule 20 by adhesion.
[0055] The multi-fiber optical connector 10 is optically connected
with the identical multi-fiber optical connector, both facing each
other. Because of this, guide pin insertion holes 23 are formed in
the end face 25 for connection of the ferrule 20. When the
multi-fiber optical connectors 10 are optically connected, guide
pins (not shown) for positioning are inserted into the guide pin
insertion holes 23.
[0056] It is possible to compose such a ferrule 20 using, for
example, an epoxy base resin material containing glass.
[0057] As shown in FIGS. 2A and 2B, the optical fiber 30 is
constituted by a clad part 31 and a core part 32 located
substantially in the center of the clad part 31. A diameter D1 of
the clad part 31 is, for example, about 125 .mu.m and a diameter D2
of the core part 32 is, for example, about 50 .mu.m or 62.5 .mu.m.
The optical fiber 30 is a so-called multi-mode optical fiber.
[0058] A method of polishing an end face of the multi-fiber optical
connector 10 as described above is explained next.
[0059] A plurality of or many multi-mode optical fibers 30 are
arranged in the optical fiber insertion holes 21 of the ferrule 20.
Next, the adhesive 40 is injected through the adhesion injection
hole 22. Due to this, the optical fibers 30 are fixed on the
ferrule 20 by adhesion. That is, the multi-fiber optical connector
10 is constructed.
[0060] At this time, the adhesive 40 injected through the adhesive
injection hole 22 passes through the optical fiber insertion holes
21 and overflows from the tip openings. The adhesive 40 having
overflowed covers the tip part 35 of the optical fibers that
project outwardly from the end face 25 for connection of the
ferrule 20.
[0061] First of all, a step of removing adhesive of the multi-fiber
optical connector 10 is carried out. As shown in FIGS. 3A and 3B,
the adhesive 40 that covers the tip parts 35 of the optical fibers
projecting outwardly from the end face 25 for connection of the
ferrule 20 is removed. FIGS. 3A and 3B schematically show the
relevant parts of the multi-fiber optical connector 10. Because of
this, the shape and dimensions of each part are shown exaggerated
for easier understanding.
[0062] As shown in FIG. 3A, a rubber pad 51 is mounted on a
polishing base (basement) 50 of a polishing machine. On the rubber
pad 51, a polishing sheet 52 is mounted. The multi-fiber optical
connector 10 is arranged so that the tip parts 35 of the optical
fibers come into contact or the adhesive 40 that covers the tip
parts 35 comes into contact with the upper surface of the polishing
sheet 52 with a predetermined pressure. In a state where the
contact is maintained, the polishing base 50 moves so that the
center axis line of the polishing base 50 describes a circular
locus while keeping a rotation-preventing attitude. Alternatively,
the multi-fiber optical connector 10 moves so that the center axis
line of the multi-fiber optical connector 10 describes a circular
locus while keeping a rotation-preventing attitude. By the movement
of the polishing base 50 or the multi-fiber optical connector 10,
the adhesive 40 that covers the tip parts 35 of the optical fibers
are polished. Due to this, the adhesive 40 is removed.
[0063] At this time, the tip parts 35 of the optical fibers are
pressed against the polishing sheet 52 by a comparatively strong
force. This force can be weakened by the deformation of the rubber
pad 51. Accordingly, excessive load is not put on the optical
fibers 30. Therefore, it is possible to prevent cracks in the
multi-mode optical fibers 30 and to remove the adhesive 40
properly.
[0064] FIG. 3B shows a state where the adhesive 40 has been
removed.
[0065] Next, a surface polishing step of the multi-fiber optical
connector 10 is carried out. As shown in FIGS. 4A and 4B, the end
face 25 for connection of the ferrule 20 is polished into a flat
surface. FIGS. 4A and 4B schematically show the relevant parts of
the multi-fiber optical connector 10. Because of this, the shape
and dimensions of each part are shown exaggerated for easier
understanding.
[0066] As shown in FIG. 4A, the polishing sheet 52 is mounted on
the polishing base (basement) 50 of the polishing machine. The
multi-fiber optical connector 10 is arranged so that the tip parts
35 of the optical fibers come into contact with the upper surface
of the polishing sheet 52 with a predetermined pressure. In a state
where the contact is maintained, the polishing base 50 moves so
that the center axis line of the polishing base 50 describes a
circular locus while keeping a rotation-preventing attitude.
Alternatively, the multi-fiber optical connector 10 moves so that
the center axis line of the multi-fiber optical connector 10
describes a circular locus while keeping a rotation-preventing
attitude. By the movement of the polishing base 50 or the
multi-fiber optical connector 10, the tip parts 35 of the
multi-mode optical fibers 30 that project from the end face 25 for
connection of the ferrule 20 are polished. Accordingly, the tip
parts 35 of the multi-mode optical fibers 30 that project from the
end face 25 for connection of the ferrule 20 are completely removed
and the end face 25 for connection of the ferrule 20 becomes almost
flat.
[0067] The state when the surface polishing step is completed is
shown in FIG. 4B.
[0068] Next, the projection step of the multi-fiber optical
connector 10 is carried out. As shown in FIGS. 5A and 5B, the tip
parts 35 of the multi-mode optical fibers 30 project by a
predetermined length from the end face for connection of the
ferrule 20. FIGS. 5A and 5B schematically show the relevant parts
of the multi-fiber optical connector 10. Because of this, the shape
and dimensions of each part are shown exaggerated for easier
understanding.
[0069] As shown in FIG. 5A, a polishing sheet 53 for buffing using
a fine-grain abrasive is mounted on the polishing base (basement)
50 of the polishing machine. The multi-fiber optical connector 10
is arranged so that the end face 25 for connection of the ferrule
20 comes into contact with the upper surface of the polishing sheet
53 with a predetermined pressure. In a state where the contact is
maintained, the polishing base 50 moves so that the center axis
line of the polishing base 50 describes a circular locus while
keeping a rotation-preventing attitude. Alternatively, the
multi-fiber optical connector 10 moves so that the center axis line
of the multi-fiber optical connector 10 describes a circular locus
while keeping a rotation-preventing attitude. By the movement of
the polishing base 50 or the multi-fiber optical connector 10, the
end face 25 for connection of the ferrule 20 is polished. Due to
this, part of the ferrule is removed.
[0070] As a result, the tip parts 35 of the multi-mode optical
fibers 30 project by a predetermined length from the end face 25
for connection of the ferrule 20.
[0071] The state when the projection step is completed is shown in
FIG. 5B.
[0072] FIG. 6 is an enlarged sectional view of the tip part 35 of
one multi-mode optical fiber 30 after the multi-fiber optical
connector 10 shown in FIG. 5B is reversed upside down.
[0073] In the case of the multi-mode optical fiber 30, the diameter
of the core part 32 is by far larger than that of the SM fiber. The
hardness of the core part 32 is less than that of the clad part 31.
Because of this, by buffing in the projection process, a large and
deep recess is produced in the tip of the core part 32 as shown in
FIG. 6.
[0074] Such a large and deep recess 33 brings about a problem when
the identical multi-fiber optical connectors 10 are connected
optically. That the contact force between the multi-mode optical
fibers 30 is weak substantially causes a gap to be produced between
the tips of the multi-mode optical fibers 30. Such a gap
considerably increases connection loss, in particular, return loss,
in the optical connection between the multi-fiber optical
connectors 10.
[0075] In order to solve this problem, the recess 33 produced in
the core part 32 of the multi-mode optical fiber 30 is eliminated
as shown in FIG. 7. FIG. 7 schematically shows relevant parts of
the multi-fiber optical connector 10. Because of this, the shape
and dimensions of each part are shown exaggerated for easier
understanding.
[0076] As shown in FIG. 7, a soft material 55 having a Shore
hardness of less than 30 is mounted on the polishing base
(basement) 50 of the polishing machine. On the soft material 55, a
film 56 having a thickness of less than 75 .mu.m without a
polishing material is mounted. A polishing material (abrasive
grain) is supplied on the upper surface of the film 56. The
multi-fiber optical connector 10 is arranged so that the tip parts
35 of the optical fibers come into contact with the upper surface
of the film 56 with a predetermined pressure. In a state where the
contact is maintained, the polishing base 50 moves so that the
center axis line of the polishing base 50 describes a circular
locus while keeping a rotation-preventing attitude. Alternatively,
the multi-fiber optical connector 10 moves so that the center axis
line of the multi-fiber optical connector 10 describes a circular
locus while keeping a rotation-preventing attitude. By the movement
of the polishing base 50 or the multi-fiber optical connector 10,
the tip ends of the multi-mode optical fibers 30 are polished. Due
to this, the recesses 33 in the tip of the core parts 32 of the
optical fibers (MM fibers) 30 are removed.
[0077] The soft material 55 is composed of, for example, a spongy
porous substance. The soft material (soft pad) 55 has a Shore
hardness of less than 30. Actually, it is preferable that the soft
material (soft pad) 55 be very soft as a sponge. In addition, it is
preferable that the soft material (sponge pad) 55 has a thickness
of, for example, about several millimeters.
[0078] The film 56 is composed of, for example, a polyethylene
terephthalate film (PET film) at least one side of which has been
primary-coated. The primary coating here refers to making coarse by
surface processing. The thickness of the film (PET film) 56 is less
than 75 .mu.m. Actually, it is preferable that the thickness of the
film (PET film) 56 be about 25 .mu.m. It is also preferable that
the film (PET film) 56 be placed with the primary-coated surface
(coarsened surface) face-up. The polishing material (polishing
grain) 60 is supplied to the surface (coarsened surface).
[0079] It is preferable to use a fine-grain abrasive (abrasive
grain) as the polishing material (polishing grain) 60. Here, a
fine-grain abrasive refers to a polishing material (polishing
grain) having an average grain diameter of 0.5 .mu.m or less.
Preferably, the polishing material (polishing grain) 60 is applied
to the primary-coated surface (coarsened surface) of the film
56.
[0080] By the polishing shown in FIG. 7, the recesses 33 in the tip
of the core parts 32 of the multi-mode optical fibers 30 are
eliminated.
[0081] FIG. 8 is an enlarged sectional view of the tip part 35 of
the multi-mode optical fiber 30 for which the polishing shown in
FIG. 7 has been completed. It can be seen that not only the recess
33 in the core part 32 is eliminated from the tip of the multi-mode
optical fiber 30 but also the tip is formed into a convex spherical
surface with the core part 32 as its vertex. The polishing shown in
FIG. 7 polishes the tip of the multi-mode optical fibers into a
convex spherical surfaces with the core parts 32 as its vertex.
Example 1
[0082] On the polishing base 50 of the polishing machine, the
sponge (sponge pad) 55 having a Shore hardness of less than 30 and
a thickness of 5 mm was mounted. On the sponge pad 55, the
polyethylene terephthalate film (PET film) 56 having a thickness of
25 .mu.m and one side of which had been primary-coated (coarsened
by surface processing) was mounted. The PET film 56 was placed with
the primary-coated surface (coarsened surface) face-up. The
fine-grain abrasive (abrasive grain) 60 was applied to the upper
surface (primary-coated surface) of the PET film 56.
[0083] The multi-fiber optical connector 10 was arranged so that
the tip parts 35 of the multi-mode optical fibers 30 came into
contact with the upper surface of the PET film 56 with a
predetermined pressure.
[0084] In a state where each of the contact between the tip of the
multi-mode optical fibers 30 and the upper surface of the PET film
56 was maintained, the polishing base 50 moved so that the center
axis line of the polishing base 50 described a circular locus while
keeping a rotation-preventing attitude.
[0085] As a result, in the multi-mode optical fibers 30, the tip of
the clad parts 31 that projected more than the tip of the core
parts 32 were polished first. As a result, the recesses 33 in the
core parts 32 were eliminated.
[0086] Alternatively, instead of the polishing base 50 left at
rest, the multi-fiber optical connector 10 moved so that the center
axis line of the multi-fiber optical connector 10 described a
circular locus while keeping a rotation-preventing attitude.
[0087] In this case also, in the multi-mode optical fibers 30, the
tip of the clad parts 31 that projected more than the tip of the
core parts 32 were polished first. As a result, the recesses 33 in
the core parts 32 were eliminated.
[0088] When either of the polishing base 50 or the multi-fiber
optical connector 10 moved, a convex spherical surfaces with the
core parts 32 as its vertex were formed at the tip of the
multi-mode optical fibers 30 of the obtained multi-fiber optical
connector 10.
[0089] When the multi-fiber optical connectors 10 were connected
optically, both connection loss and return loss fell in a
predetermined permitted range. In particular, the return loss was
equal to or more than 40 dB and an excellent result was
obtained.
Comparative Example 1
[0090] On the polishing base 50 of the polishing machine, a rubber
pad having a Shore hardness of 30 and a thickness of 5 mm was
mounted. On the rubber pad, the polyethylene terephthalate film
(PET film) 56 having a thickness of 25 .mu.m and one side of which
had been primary-coated (coarsened by surface processing) was
mounted. The PET film 56 was placed with the primary-coated surface
(coarsened surface) face-up. The fine-grain abrasive (abrasive
grain) 60 was applied to the upper surface (primary-coated surface)
of the PET film 56.
[0091] The multi-fiber optical connector 10 was arranged so that
the tip parts 35 of the multi-mode optical fibers 30 came into
contact with the upper surface of the PET film 56 with a
predetermined pressure.
[0092] In a state where each of the contact between the tip of the
multi-mode optical fibers 30 and the upper surface of the PET film
56 was maintained, the polishing base 50 moved so that the center
axis line of the polishing base 50 described a circular locus while
keeping a rotation-preventing attitude.
[0093] However, in the multi-mode optical fibers 30, the recesses
33 produced in the tip of the core parts 32 in the projection step
were not eliminated completely but a portion of them was left.
[0094] Alternatively, instead of the polishing base 50 left at
rest, the multi-fiber optical connector 10 moved so that the center
axis line of the multi-fiber optical connector 10 described a
circular locus while keeping a rotation-preventing attitude.
[0095] In this case also, in the multi-mode optical fibers 30, the
recesses 33 in the tip of the core parts 32 were not eliminated
completely but a portion of them was left.
[0096] When either of the polishing base 50 or the multi-fiber
optical connector 10 moved, part of the recess 33 in the core part
32 was left in the tip of the multi-mode optical fiber 30 of the
obtained multi-fiber optical connector 10.
[0097] When the multi-fiber optical connectors 10 were connected
optically, both connection loss and return loss varied
considerably. In particular, the return loss varied in the range of
15 to 35 dB and some deviated from a predetermined permitted
range.
Example 2
[0098] On the polishing base 50 of the polishing machine, the
sponge (sponge pad) 55 having a Shore hardness of less than 30 and
a thickness of 5 mm was mounted. On the sponge pad 55, the
polyethylene terephthalate film (PET film) 56 having a thickness of
75 .mu.m and one side of which had been primary-coated (coarsened
by surface processing) was mounted. The PET film 56 was placed with
the primary-coated surface (coarsened surface) face-up. The
fine-grain abrasive (abrasive grain) 60 was applied to the upper
surface (primary-coated surface) of the PET film 56.
[0099] The multi-fiber optical connector 10 was arranged so that
the tip parts 35 of the multi-mode optical fibers 30 came into
contact with the upper surface of the PET film 56 with a
predetermined pressure.
[0100] In a state where each of the contact between the tip of the
multi-mode optical fibers 30 and the upper surface of the PET film
56 was maintained, the polishing base 50 moved so that the center
axis line of the polishing base 50 described a circular locus while
keeping a rotation-preventing attitude.
[0101] As a result, in the multi-mode optical fibers 30, the tip of
the clad parts 31 that projected more than the tip of the core
parts 32 were polished first. As a result, the recesses 33 in the
core parts 32 were eliminated.
[0102] Alternatively, instead of the polishing base 50 left at
rest, the multi-fiber optical connector 10 moved so that the center
axis line of the multi-fiber optical connector 10 described a
circular locus while keeping a rotation-preventing attitude.
[0103] In this case also, in the multi-mode optical fibers 30, the
tip of the clad parts 31 that projected more than the tip of the
core parts 32 were polished first. As a result, the recesses 33 in
the core parts 32 were eliminated.
[0104] When either of the polishing base 50 or the multi-fiber
optical connector 10 moved, a convex spherical surfaces with the
core parts 32 as its vertex were formed at the tip of the
multi-mode optical fibers 30 of the obtained multi-fiber optical
connector 10.
[0105] When the multi-fiber optical connectors 10 were connected
optically, both connection loss and return loss fell in a
predetermined permitted range. In particular, the return loss was
equal to or more than 35 dB and an excellent result was
obtained.
Comparative Example 2
[0106] On the polishing base 50 of the polishing machine, the
sponge (sponge pad) 55 having a Shore hardness of less than 30 and
a thickness of 5 mm was mounted. On the sponge pad 55, the
polyethylene terephthalate film (PET film) 56 having a thickness of
75 .mu.m and containing a polishing material (abrasive grain) was
mounted.
[0107] The multi-fiber optical connector 10 was arranged so that
the tip parts 35 of the multi-mode optical fibers 30 came into
contact with the upper surface of the PET film 56 with a
predetermined pressure.
[0108] In a state where each of the contact between the tip of the
multi-mode optical fibers 30 and the upper surface of the PET film
56 was maintained, the polishing base 50 moved so that the center
axis line of the polishing base 50 described a circular locus while
keeping a rotation-preventing attitude.
[0109] However, in the multi-mode optical fibers 30, the recesses
33 produced in the tip of the core parts 32 in the projection step
were not eliminated completely but a portion of them was left.
[0110] Alternatively, instead of the polishing base 50 left at
rest, the multi-fiber optical connector 10 moved so that the center
axis line of the multi-fiber optical connector 10 described a
circular locus while keeping a rotation-preventing attitude.
[0111] In this case also, in the multi-mode optical fibers 30, the
recesses 33 in the tip of the core parts 32 were not eliminated
completely but a portion of them was left.
[0112] When either of the polishing base 50 or the multi-fiber
optical connector 10 moved, part of the recess 33 in the core part
32 was left in the tip of the multi-mode optical fiber 30 of the
obtained multi-fiber optical connector 10.
[0113] When the multi-fiber optical connectors 10 were connected
optically, both connection loss and return loss varied
considerably. In particular, the return loss varied in the range of
15 to 35 dB and some deviated from a predetermined permitted
range.
Comparative Example 3
[0114] On the polishing base 50 of the polishing machine, a rubber
pad having a Shore hardness of 80 and a thickness of 5 mm was
mounted. On the rubber pad, the polyethylene terephthalate film
(PET film) 56 having a thickness of 75 .mu.m and containing a
polishing material (abrasive grain) was mounted.
[0115] The multi-fiber optical connector 10 was arranged so that
the tip parts 35 of the multi-mode optical fibers 30 came into
contact with the upper surface of the PET film 56 with a
predetermined pressure.
[0116] In a state where each of the contact between the tip of the
multi-mode optical fibers 30 and the upper surface of the PET film
56 was maintained, the polishing base 50 moved so that the center
axis line of the polishing base 50 described a circular locus while
keeping a rotation-preventing attitude.
[0117] However, in the multi-mode optical fibers 30, the recesses
33 produced in the tip of the core parts 32 in the projection step
were hardly eliminated and remained substantially the same as that
before polishing.
[0118] Alternatively, instead of the polishing base 50 left at
rest, the multi-fiber optical connector 10 moved so that the center
axis line of the multi-fiber optical connector 10 described a
circular locus while keeping a rotation-preventing attitude.
[0119] In this case also, in the multi-mode optical fibers 30, the
recesses 33 in the tip of the core parts 32 was hardly eliminated
and remained substantially the same as that before polishing.
[0120] When either of the polishing base 50 and the multi-fiber
optical connector 10 moved, the recesses 33 in the core parts 32
remained substantially the same as that before polishing in the tip
of the multi-mode optical fibers 30 of the obtained multi-fiber
optical connector 10.
[0121] When the multi-fiber optical connectors 10 were connected
optically, both connection loss and return loss deviated
considerably from a predetermined permitted range. In particular,
the return loss was 15 dB or less, considerably lower than a
predetermined permitted range.
[0122] According to the present invention, it is possible to
effectively eliminate recesses produced in the tip of the core
parts 32 of the multi-mode optical fibers 30 in the projection step
following the surface polishing step of the multi-fiber optical
connector 10.
[0123] In addition to the above, a convex spherical surfaces with
the core parts 32 as its vertex are formed at the tip of the
multi-mode optical fibers 30 of the multi-fiber optical connector
10.
* * * * *