U.S. patent application number 10/160064 was filed with the patent office on 2002-10-10 for optical fiber connector, ferrule used therefor and method for manufacturing ferrule.
This patent application is currently assigned to Tetsuo Tanaka. Invention is credited to Okamoto, Shinichi, Tanaka, Tetsuo.
Application Number | 20020146214 10/160064 |
Document ID | / |
Family ID | 18505416 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020146214 |
Kind Code |
A1 |
Tanaka, Tetsuo ; et
al. |
October 10, 2002 |
Optical fiber connector, ferrule used therefor and method for
manufacturing ferrule
Abstract
Electroforming is performed in an electroforming bath with a
cathode of a metal wire member immersed in an electroforming
solution to electrodeposit nickel around the aluminum alloy wire
member. The aluminum alloy wire member is removed by dissolution
with an alkaline solution from an obtained nickel electroformed
product. Accordingly, a nickel cylinder is obtained, which has a
through-hole formed corresponding to the wire member. The cylinder
is cut into those having a predetermined length. The outer
circumference is subjected to cutting based on the through-hole to
obtain a ferrule. The inner diameter accuracy of the through-hole
of the ferrule is determined by the outer diameter accuracy of the
wire member. Therefore, it is unnecessary to perform polishing for
the through-hole. The highly accurate ferrule is obtained in
accordance with the simple process at low cost. The PC polishing
for the ferrule for effecting PC junction of optical fibers is
extremely easy, because the ferrule is made of metal. Thus, it is
possible to provide a high performance optical fiber connector.
Inventors: |
Tanaka, Tetsuo;
(Utsunomiya-shi, JP) ; Okamoto, Shinichi;
(Hasuda-shi, JP) |
Correspondence
Address: |
NIXON & VANDERHYE P.C.
8th Floor
1100 North Glebe Road
Arlington
VA
22201-4714
US
|
Assignee: |
Tetsuo Tanaka
|
Family ID: |
18505416 |
Appl. No.: |
10/160064 |
Filed: |
June 4, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10160064 |
Jun 4, 2002 |
|
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09449999 |
Nov 26, 1999 |
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6419810 |
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Current U.S.
Class: |
385/78 ; 205/67;
205/76; 385/60 |
Current CPC
Class: |
G02B 6/3807 20130101;
G02B 6/3893 20130101; G02B 6/3825 20130101; G02B 6/3833 20130101;
C25D 1/02 20130101 |
Class at
Publication: |
385/78 ; 205/67;
205/76; 385/60 |
International
Class: |
G02B 006/36; C25D
001/00; G02B 006/38; C25D 001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 1998 |
JP |
10-375372 |
Claims
What is claimed is:
1. A method for producing a ferrule which is used for connecting
optical fibers, the method comprising: depositing a metal by means
of electroforming around at least one wire member to produce a
rod-shaped electroformed product; and removing the wire member from
the electroformed product.
2. The method for producing the ferrule according to claim 1,
wherein the wire member has a circular cross section and a diameter
of the wire member is not more than 0.13 mm.
3. The method for producing the ferrule according to claim 1,
further comprising cutting an outer circumference of the
electroformed product about a center of a through-hole formed by
removing the wire member from the electroformed product.
4. The method for producing the ferrule according to claim 1,
wherein the wire member is a wire member made of metal or
plastic.
5. The method for producing the ferrule according to claim 1,
wherein that the wire member is removed from the electroformed
product by dissolving the wire member with an alkaline or acidic
solution after the electroforming.
6. The method for producing the ferrule according to claim 5,
wherein the wire member is made of aluminum or alloy thereof.
7. The method for producing the ferrule according to claim 1,
wherein a mold release treatment is applied to the wire member
before the electroforming, and the wire member is removed from the
electroformed product by extracting the wire member from the
electroformed product after the electroforming.
8. The method for producing the ferrule according to claim 7,
wherein the wire member is made of iron or alloy thereof.
9. The method for producing the ferrule according to claim 1,
wherein a mold release treatment is applied to the wire member
before the electroforming, and the wire member is removed from the
electroformed product by extruding the wire member from the
electroformed product after the electroforming.
10. The method for producing the ferrule according to claim 1,
wherein the at least one wire member is two wire members which are
arranged to be separated from each other by a predetermined
distance.
11. The method for producing the ferrule according to claim 10,
wherein the two wire members are positioned so that a pin having a
predetermined size is interposed thereby.
12. The method for producing the ferrule according to claim 1,
wherein the at least one wire member is three wire members which
are arranged to be separated from each other by an identical
distance.
13. The method for producing the ferrule according to claim 1,
wherein the metal is one selected from the group consisting of
aluminum, nickel, iron, copper, cobalt, tungsten, and alloys
thereof.
14. The method for producing the ferrule according to claim 1,
wherein the metal is nickel.
15. The method for producing the ferrule according to claim 1,
further comprising cutting the electroformed product into those
having a predetermined length.
16. A metal ferrule produced in accordance with the method as
defined in claim 1.
17. The metal ferrule according to claim 16, wherein the ferrule
has a columnar hollow section which penetrates in a longitudinal
direction of the ferrule, the ferrule has, at its first end, a
first opening which has the same diameter as that of the hollow
section, and the ferrule has, at its second end, a second opening
which has a diameter larger than the diameter of the hollow
section.
18. The metal ferrule according to claim 17, wherein the hollow
section includes a first hollow section, a second hollow section
which has a diameter larger than that of the first hollow section,
and a third hollow section having a tapered configuration which
connects the first hollow section and the second hollow
section.
19. The metal ferrule according to claim 18, wherein a coated
portion of an optical fiber is accommodated in the second hollow
section, and a clad of the optical fiber is accommodated in the
first hollow section.
20. A ferrule used for connecting optical fibers, wherein the
ferrule is integrally formed of only a metal material.
21. The ferrule according to claim 20, which is produced by
electroforming.
22. The ferrule according to claim 20, wherein the metal is one
selected from the group consisting of aluminum, nickel, iron,
copper, cobalt, tungsten, and alloys thereof.
23. The ferrule according to claim 20, wherein a plurality of
hollow sections for allowing the optical fiber to pass therethrough
are formed.
24. The ferrule according to claim 20, wherein holes for allowing
the optical fiber to penetrate therethrough have a tapered
configuration at both ends of the ferrule, and the ferrule is used
for a mechanical splice.
25. The ferrule according to claim 20, wherein the ferrule has a
columnar hollow section which penetrates in a longitudinal
direction of the ferrule, the ferrule has, at its first end, a
first opening which has the same diameter as that of the hollow
section, and the ferrule has, at its second end, a second opening
which has a diameter larger than the diameter of the hollow
section.
26. The ferrule according to claim 25, wherein the hollow section
includes a first hollow section, a second hollow section which has
a diameter larger than that of the first hollow section, and a
third hollow section having a tapered configuration which connects
the first hollow section and the second hollow section.
27. The metal ferrule according to claim 26, wherein a coated
portion of the optical fiber is accommodated in the second hollow
section, and a clad of the optical fiber is accommodated in the
first hollow section.
28. The ferrule according to claim 20, which is used for an optical
fiber connector.
29. An optical fiber connector for connecting optical fibers,
comprising: a ferrule integrally formed of only a metal material;
and a housing for accommodating the ferrule.
30. The optical fiber connector according to claim 29, wherein the
ferrule is formed by electroforming.
31. The optical fiber connector according to claim 29, further
comprising a holder for holding the ferrule and positioning the
ferrule in a rotational direction in the housing.
32. The optical fiber connector according to claim 29, further
comprising, in the ferrule, an optical fiber which is shorter than
a length of the ferrule, wherein a tip of the optical fiber and a
tip of the ferrule has been PC polished.
33. The optical fiber connector according to claim 29, wherein the
housing is a plug.
34. The optical fiber connector according to claim 29, further
comprising a sleeve for aligning the ferrule.
35. The optical fiber connector according to claim 29, wherein the
housing is a jack.
36. The optical fiber connector according to claim 33, further
comprising an adapter for making detachable connection to the plug,
the adapter having a sleeve for aligning the ferrule.
37. The optical fiber connector according to claim 29, further
comprising an optical fiber cable, wherein a tip of an optical
fiber of the optical fiber cable is located at a tip of the
ferrule.
38. The optical fiber connector according to claim 37, wherein the
tip of the optical fiber and the tip of the ferrule have been
simultaneously polished.
39. The optical fiber connector according to claim 38, wherein the
polishing is flat polishing or PC polishing.
40. A wire member-supporting apparatus for being used when a
ferrule having multiple cores for connecting optical fibers is
produced by means of electroforming, the apparatus comprising: a
base plate; a pair of first positioning projections provided
mutually opposingly on the base plate, each of the first
projections having an identical width; and two wire members
stretched in parallel to one another with the pair of first
positioning projections interposed therebetween.
41. The apparatus according to claim 40, wherein the two wire
members are positioned by the aid of the projections, and a spacing
distance between the two wire members is defined thereby.
42. The apparatus according to claim 41, wherein the two wire
members are connected at their ends respectively to form one wire
member.
43. The apparatus according to claim 40, wherein the projection is
a pin provided on the base plate.
44. The apparatus according to claim 40, further comprising a
plurality of guide pins for winding the wire member therearound in
order to maintain tension of the wire member.
45. The apparatus according to claim 40, further comprising: a pair
of second positioning projections provided mutually opposingly on
the base plate, each of the second projections having an identical
width; and two wire members stretched in parallel to one another
with the pair of second positioning projections interposed
therebetween, wherein: the wire members stretched in parallel to
one another with the first projections interposed therebetween are
mutually parallel to the wire members stretched in parallel to one
another with the second projections interposed therebetween, and
the respective adjoining wire members are separated from each other
by an identical distance.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an optical fiber connector,
a ferrule to be used for the optical fiber connector, and a method
for producing the ferrule. In particular, the present invention
relates to an optical fiber connector for correctly aligning mutual
positions of cores of optical fibers and connecting them to one
another by inserting the optical fibers into cylindrical ferrules
to support them, a ferrule to be used for the optical fiber
connector, and a method for producing the ferrule. The present
invention also relates to a wire member-supporting apparatus to be
used for producing the ferrule.
[0003] 2. Description of the Related Art
[0004] In recent years, the electric cable for the telephone line
is being replaced with the optical fiber cable on a worldwide
scale. The use of the optical fiber is not limited to the optical
communication based on the telephone. The optical fiber is also
widely used for optical devices, apparatuses for LAN, and a variety
of optical systems. Methods are known to mutually connect optical
fibers in such an optical communication system, including a
permanent connection method based on the use of fusion or
mechanical splice, and a detachable connection method based on the
use of an optical fiber connector. It is required for the optical
fiber connector used for the latter method that attachment and
detachment can be easily performed, and the optical fiber connector
is resistant to the environment. Additionally, in order to respond
to the demand for the optical communication system to realize long
distance communication and large capacity, for example, it is
required for the optical fiber connector that the connection loss
is low, and the nonreflective treatment is applied in order to
stabilize laser transmission.
[0005] Conventionally, as shown in (C) of FIG. 1, an optical fiber
connector comprises tubular parts (hereinafter referred to as
"ferrules") 1a, 1b having a perfect circular cross section for
highly accurately holding optical fibers 40a, 40b having a diameter
of about 0.13 mm at predetermined positions and fixing them
coaxially, and an aligning section 42 for holding the ferrules 1a,
1b while allowing them to make mutual abutment. For example, the
ferrule has a columnar configuration as shown in (A) of FIG. 1, and
it is made of a zirconia ceramic material or the like. The ferrule
1 shown in (A) of FIG. 1 is a ferrule of the one-core type. For
example, the ferrule 1 has a perfect circular through-hole 2 of
.phi.=0.126 mm which is formed in the longitudinal direction at the
center of the column having a length of about 8 mm. A ferrule 1'
shown in (B) of FIG. 1 is a ferrule of the two-core type. The
ferrule 1' is bored with two through-holes 2a, 2b for allowing two
optical fibers to pass therethrough.
[0006] When the ferrule as shown in (A) of FIG. 1 is produced, the
following method has been hitherto adopted. At first, a mixture of
zirconia powder and resin is used as a raw material which is molded
to have a cylindrical configuration by employing, for example, a
mold for injection molding or extrusion molding to mold the
cylindrical configuration. Subsequently, a molded product is fired
at a temperature of about 500.degree. C. to decompose the resin
component, followed by being fired at a high temperature of about
1200.degree. C. An obtained cylindrical fired product has a
through-hole into which a diamond-polishing member having a liner
configuration is inserted so that the inner diameter of the
through-hole is finely adjusted. Finally, the outer portion of the
cylindrical product is machined about the center of the inner hole
to finish the ferrule so that it has a perfect circular shape.
[0007] In the molding method described above, the fired molded
product is slightly contracted due to the firing, and the inner
diameter thereof is deviated from a desired dimension. For this
reason, the polishing process based on the use of the
diamond-polishing member, which is performed after the firing, is a
necessary and indispensable treatment. However, the polishing
process is laborious, and it requires skill, causing the decrease
in productivity. Further, it has been not easy to obtain a
perfectly uniform inner diameter concerning the position in the
axial direction of the inner hole of the fired product even when
the polishing process is performed, for example, because the
diamond is not uniformly attached to the linear polishing member.
Further, a problem arises in that the equipment cost is expensive,
because the diamond-polishing member is consumed and exhausted.
[0008] A molding machine and a mold, which are expensive and
specialized in this purpose, are required to perform the injection
molding or the extrusion molding as described above. Especially,
the molding machine and the mold are conspicuously abraded by the
extremely hard zirconia powder, and hence their service lives are
short as well. It is also possible to use a hard material for the
surfaces of the molding machine and the mold. However, the
production cost is extremely expensive for such a special molding
machine and a special mold. Further, the energy cost is increased,
and the energy source is wasted as well, because the firing is
performed at a high temperature of 500 to 1200.degree. C. in the
firing step. If the production cost of the ferrule is increased as
described above, the production cost of an optical fiber connector
including the ferrule accommodated therein is also increased.
[0009] Further, the following problem also arises. Although the
ferrule of the one-core type as shown in (A) of FIG. 1 has been
hitherto dominantly used, the ferrule of the two-core type as shown
in (B) of FIG. 1 or ferrules having more than two cores are
gradually demanded. In the case of the ferrules having two or more
cores, it is extremely difficult to perform the step to establish
the dimension by means of the polishing with the diamond-polishing
member. The production of ferrules having three or more cores has
been substantially impossible.
[0010] When optical fibers are connected to one another by using an
optical fiber connector, the process is executed by means of the
connection in which tips of the optical fibers are allowed to make
mutual abutment, i.e., so-called physical contact (hereinafter
referred to as "PC"), in order to decrease the reflection loss at
the connecting portion. In order to achieve the PC connection, the
following processing has been performed. That is, the end surface
of the ferrule is polished to have a convex spherical surface or an
oblique convex spherical surface, or the end surface of the ferrule
is polished to have a flat surface or an oblique flat surface,
together with the tip of the optical fiber in a state in which the
optical fiber is charged in the ferrule. The conventional ferrule
made of zirconia or glass has involved the problem that such
process cannot be easily performed.
[0011] In the conventional technique, when the ferrule is installed
to the optical fiber connector, then the ferrule is installed in a
holder, and it is installed to the optical fiber connector together
with the holder, in order to adjust the rotational position of the
ferrule. A problem has been also pointed out in that the number of
parts of the optical fiber connector is increased due to the use of
such a holder.
SUMMARY OF THE INVENTION
[0012] The present invention has been made in consideration of the
problems involved in the conventional technique as described above,
a first object of which is to provide a ferrule, a method for
producing the same, and an apparatus for producing the same,
wherein the ferrule can be produced at low energy cost with a
simple and cheap equipment without any necessity for the expensive
and special equipment such as a molding machine and a mold.
[0013] A second object of the present invention is to provide a
ferrule, a method for producing the same, and an apparatus for
producing the same, wherein the ferrule is excellent in dimensional
stability, and it can be produced in accordance with a process with
high productivity without necessitating any special skill of an
operator.
[0014] A third object of the present invention is to provide a
ferrule, a method for producing the ferrule, and an apparatus for
producing the ferrule, wherein the ferrule can be easily produced
even when it is designed to have multiple cores.
[0015] A fourth object of the present invention is to provide a
ferrule involving an extremely small dimensional error, if any,
wherein the ferrule can be easily produced.
[0016] A fifth object of the present invention is to provide an
optical fiber connector at low cost, which makes it possible to
connect optical fibers with high accuracy.
[0017] According to a first aspect of the present invention, there
is provided a method for producing a ferrule to be used for
connecting optical fibers, the method comprising:
[0018] depositing a metal by means of electroforming around at
least one wire member to produce a rod-shaped electroformed
product; and
[0019] removing the wire member from the electroformed product.
[0020] The method of the present invention is characterized in that
the extremely thin wire member is used as a base mold to produce
the ferrule in accordance with the electroforming method. The inner
diameter of the obtained metal tube is determined by the outer
diameter of the wire member. The inner diameter accuracy of the
metal tube is also determined by the outer diameter accuracy of the
wire member. Therefore, the ferrule, which has the extremely
excellent inner diameter accuracy, can be obtained with the wire
member which has a cross section (perfect circle) similar to that
of the optical fiber, which has a width or a diameter slightly
larger than that of the optical fiber, and which has highly
accurate linearity and roundness. The obtained ferrule includes an
inner hole which has high linearity and roundness. Therefore, it is
unnecessary to perform the polishing operation having been hitherto
performed to ensure the dimensional accuracy of the inner diameter
of the ferrule. In order to remove the wire member from the
electroformed product, only the wire member may be dissolved out of
the electroformed product, or the wire member is extracted or
extruded from the electroformed product, after the metal is
deposited around the wire member in accordance with the
electroforming. Accordingly, it is possible to obtain the
cylindrical metal tube which is formed with the through-hole
corresponding to the cross-sectional shape of the wire member. It
is desirable that the wire member to be used is a wire member
having an outer diameter of not more than 0.2 mm, especially not
more than 0.13 mm.
[0021] In order to obtain the ferrule by machining the
electroformed product, the electroformed product is cut into those
having a predetermined length. The outer circumference of the
electroformed product may be subjected to cutting about the center
of a through-hole which is formed by removing the wire member from
the electroformed product.
[0022] In the method of the present invention, for example, when
the wire member is made of aluminum or alloy thereof, it is
preferable that the wire member is removed from the electroformed
product by dissolving the wire member with an alkaline or acidic
solution after the electroforming. When the wire member is made of
iron or alloy thereof, it is preferable that a mold release
treatment is applied to the wire member before the electroforming,
and the wire member is removed from the electroformed product by
extracting or extruding the wire member from the electroformed
product after the electroforming.
[0023] In the method of the present invention, a two-core ferrule
may be produced by arranging two wire members so that they are
separated from each other by a predetermined distance to perform
the electroforming. In this procedure, the two wire members are
arranged so that a pair of pins each having an identical diameter
are interposed by the wire members, and thus the spacing distance
between the two wire members can be controlled easily and highly
accurately. A ferrule having three or more cores can be also
produced such that three or more wire members are arranged in
parallel to one another while being separated from each other by an
identical spacing distance, for example, with two or more pins.
[0024] According to a second aspect of the present invention, there
is provided a metal ferrule produced in accordance with the method
according to the first aspect.
[0025] According to a third aspect of the present invention, there
is provided a ferrule to be used for connecting optical fibers, the
ferrule being formed of only a metal material in an integrated
manner.
[0026] The metal ferrule of the present invention can be produced,
for example, by means of the electroforming method of the present
invention extremely accurately, easily, and cheaply. When two
optical fibers are joined to one another via an optical fiber
connector which accommodates the ferrule, the tip of the ferrule is
polished together with the optical fiber for the purpose of flat
junction or PC junction. The ferrule of the present invention is
polished extremely easily, because it is made of metal. The
polishing operation, which is highly accurately controlled, can be
applied to the ferrule of the present invention. Therefore, it is
possible to perform the PC junction in a well suited manner, and it
is possible to join optical fibers with low reflection loss.
[0027] The ferrule of the present invention has, at its both ends,
holes for allowing the optical fiber to penetrate therethrough, the
holes being machined to have a tapered configuration, and it may be
used as a sleeve for a mechanical splice.
[0028] The ferrule may have a columnar hollow section penetrating
in a longitudinal direction of the ferrule, the ferrule may have,
at its first end, a first opening which has the same diameter as
that of the hollow section, and the ferrule may have, at its second
end, a second opening which has a diameter larger than the diameter
of the hollow section (see FIG. 20). The hollow section may include
a first hollow section, a second hollow section which has a
diameter larger than that of the first hollow section, and a third
hollow section having a tapered configuration which connects the
first hollow section and the second hollow section. In this
arrangement, a coated portion of the optical fiber is accommodated
in the second hollow section, and a clad of the optical fiber is
accommodated in the first hollow section. That is, the second
hollow section functions as a conventional ferrule holder. The
third hollow section facilitates the introduction of the clad of
the optical fiber into the first hollow section.
[0029] According to a third aspect of the present invention, there
is provided an optical fiber connector for connecting optical
fibers, comprising:
[0030] a ferrule formed of only a metal material in an integrated
manner; and
[0031] a housing for accommodating the ferrule.
[0032] The polishing process for PC connection can be carried out
easily and highly accurately, because the optical fiber connector
of the present invention includes the ferrule made of metal.
Therefore, it is possible to realize the optical fiber connector
with low reflection loss at low cost. The metal ferrule described
above is preferably produced by means of the electroforming method
according to the present invention.
[0033] The housing of the optical fiber connector of the present
invention may function as a plug or a jack. The optical fiber
connector may further comprise a sleeve for aligning two ferrules.
The optical fiber connector may further comprise an adapter for
making detachable connection to the plug. In this arrangement, the
adapter may include a sleeve for aligning the ferrule at its
inside. The optical fiber connector may further comprise an optical
fiber cable.
[0034] According to a fourth aspect of the present invention, there
is provided a wire member-supporting apparatus for being used when
a ferrule having multiple cores for connecting optical fibers is
produced by means of electroforming, the apparatus comprising:
[0035] a base plate;
[0036] a pair of first positioning projections provided mutually
opposingly on the base plate, each of the first projections having
an identical width; and
[0037] two wire members stretched in parallel to one another with
the pair of first positioning projections interposed
therebetween.
[0038] The apparatus of the present invention is extremely
effective to be used for the production of the ferrule having the
multiple cores, the apparatus being installed in an electroforming
bath. The two wire members contact with the projections, for
example, such that they are urged against the projections such as
reference pins provided on the base plate, in mutually opposite
directions. Therefore, the wire members are positioned at both
sides of the projections respectively. Accordingly, the spacing
distance between the two wire members is highly accurately managed
in accordance with the diameter of the reference pin. In order to
change the spacing distance between a plurality of inner holes
formed in the ferrule having the multiple cores, reference pins
having a variety of diameters may be previously prepared, and the
reference pins may be appropriately exchanged depending on the
spacing distance between the inner holes.
[0039] The apparatus may further comprise a pair of second
positioning projections provided mutually opposingly on the base
plate, each of the second projections having an identical width,
and two wire members stretched in parallel to one another with the
pair of second positioning projections interposed therebetween,
wherein the wire members stretched in parallel to one another with
the first projections interposed therebetween are mutually parallel
to the wire members stretched in parallel to one another with the
second projections interposed therebetween, and the respective
adjoining wire members are arranged and separated from each other
by an identical distance. Accordingly, it is possible to produce a
ferrule of the four-core type in which four inner holes are formed
and arranged to give an identical spacing distance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 shows cross-sectional views illustrating an optical
fiber connector and ferrules, wherein (A) of FIG. 1 shows a
longitudinal sectional view of a one-core type ferrule and a
sectional view thereof taken in an X-X direction, (B) of FIG. 1
shows a longitudinal sectional view of a two-core type ferrule and
a sectional view thereof taken in an X-X direction, and (C) of FIG.
1 shows a schematic sectional view illustrating the optical fiber
connector for connecting optical fibers.
[0041] FIG. 2 shows a schematic arrangement of an electroforming
apparatus according to an embodiment of the present invention.
[0042] FIG. 3 shows a side view (A) and a plan view (B)
illustrating a support jig to be used for the apparatus shown in
FIG. 2.
[0043] FIG. 4 shows a specified embodiment of the supporting jig
which is usable for the apparatus shown in FIG. 2, depicting a side
view illustrating the support jig suitable to produce the two-core
type ferrule.
[0044] FIG. 5 shows sectional views (A) to (F) of a variety of
wires of those of the multiple-core type other than those having a
circular cross section according to the present invention.
[0045] FIG. 6 conceptually illustrates a procedure for extruding
the wire from an electroformed product in accordance with the
method of the present invention.
[0046] FIG. 7 conceptually illustrates the provision of tapes 20
disposed at predetermined spacing distances on the wire when the
wire is extracted from the electroformed product in accordance with
the method of the present invention.
[0047] FIG. 8 conceptually shows the wire in a state in which the
tape 20 illustrated in FIG. 7 has been peeled off after the
electroforming.
[0048] FIG. 9 conceptually illustrates a procedure for extracting
the wire from the electroformed product by using a jig when the
wire is extracted from the electroformed product in accordance with
the method of the present invention.
[0049] FIG. 10 shows a plan view illustrating a schematic
arrangement of a support jig to be used in the fourth embodiment of
the present invention.
[0050] FIG. 11 conceptually shows a wire to be attached to the
support jig shown in FIG. 10.
[0051] FIG. 12 shows a plan view (A) and a side view (B)
illustrating a hook to be attached to the support jig shown in FIG.
10.
[0052] FIG. 13 shows a sectional view illustrating an electroformed
product obtained in the fourth embodiment.
[0053] FIG. 14 conceptually shows a part of a wire support jig to
be used to produce a ferrule having three or more cores.
[0054] FIG. 15 illustrates an exemplary structure of a sleeve for a
mechanical splice, wherein (A) of FIG. 15 shows a sectional view of
the sleeve, and (B) of FIG. 15 shows a method for permanently
connecting two optical fibers with the sleeve.
[0055] FIG. 16 shows a schematic sectional view illustrating a
structure of an optical fiber connector plug according to the
present invention.
[0056] FIG. 17 shows a schematic sectional view illustrating a
structure of an optical fiber connector according to the present
invention.
[0057] FIG. 18 shows a schematic sectional view illustrating a
structure of an optical fiber connector-equipped optical cable
according to the present invention.
[0058] FIG. 19 shows a sectional structure of a ferrule obtain by
performing the electroforming with an apparatus described in the
sixth embodiment, followed by machining to give a rectangular
parallelepiped-shaped contour.
[0059] FIG. 20 shows a structure and a method of use of an
integrated type ferrule comprising a ferrule and a conventional
ferrule holder which are formed in an integrated manner.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
[0060] At first, explanation will be made with reference to FIG. 2
for an apparatus for producing the ferrule of the present invention
by means of the electroforming. The apparatus shown in FIG. 2
comprises an electroforming bath 50, an electroforming solution 3
charged in the electroforming bath 50, and anodes 4 and a cathode 8
which are arranged in the electroforming bath 50. The four anodes 4
are provided to surround the cathode on a base 52 which is
installed on the bottom of the electroforming bath 50. As described
later on, the cathode 8 is provided on a support jig 5, and it is
electrically connected to a wire member 9 which is stretched
between upper and lower ends of the support jig 5. Air nozzles 6,
which are provided on the base 52, are disposed at intervals of 90
degrees in the circumferential direction of the wire member 9.
[0061] The electroforming solution 3 is determined depending on the
quality of the metal material to be subjected to the electroforming
around the wire member 9, for which it is possible to use, for
example, a metal for electroforming such as nickel or alloy
thereof, iron or alloy thereof, copper or alloy thereof, cobalt or
alloy thereof, tungsten alloy, and fine particle-dispersed metal.
Those usable for the electroforming solution 3 include a solution
containing a major component of an aqueous solution of nickel
sulfamate, nickel chloride, nickel sulfate, ferrous sulfamate,
ferrous borofluoride, copper pyrophosphate, copper sulfate, copper
borofluoride, copper silicofluoride, copper titanofluoride, copper
alkanolsulfonate, cobalt sulfate, sodium tungstate or the like, and
a solution obtained by dispersing, in the foregoing solution, fine
powder of silicon carbide, tungsten carbide, boron carbide,
zirconium oxide, silicon nitride, alumina, diamond or the like.
Among them, a bath containing a major component of nickel sulfamate
is especially appropriate in view of the easiness of the
electroforming, the small stress of the electroformed product, the
chemical stability, and the easiness of welding.
[0062] The metal component of the electroforming solution serves as
a material for constituting the electroformed product, i.e., the
ferrule. As described later on, the ferrule is subjected to the PC
polishing in order to effect the PC connection. In view of the PC
polishing, it is especially preferred to use a nickel/cobalt alloy
as the metal component.
[0063] The electroforming solution may be filtrated at a high speed
in the electroforming bath with a filter (not shown) having a
filtration accuracy of about 0.1 to 2 .mu.m, and it may be heated
so that its temperature may be controlled to be within a proper
temperature range of about 50.+-.5.degree. C. It is preferable that
an active carbon treatment may be occasionally applied to remove
organic impurities. It is desirable that the electric power is
applied at a low current density of about 0.2 A/dm.sup.2 to remove
metal impurities such as copper from the electroforming solution in
the bath by using carbon as an anode and a corrugated sheet made of
iron plated with nickel as a cathode.
[0064] The anode 4 is selected depending on the metal intended to
be electroformed, which is selected, for example, from nickel,
iron, copper, and cobalt. Those having a plate-shaped configuration
or a spherical configuration may be appropriately used. When the
spherical electrodes are used, for example, the spheres may be used
such that they are placed in a basket made of titanium, and they
are covered with a bag made of polyester.
[0065] The support jig 5 will be explained in detail with reference
to FIG. 3. (A) of FIG. 3 shows a side view, and (B) of FIG. 3 shows
a sectional view of a lower plate 11 as viewed in a direction of
B-B. The support jig 5 comprises an upper plate 10 and the lower
plate 11 which are coupled to one another with four support pillars
12 intervening therebetween. Each of the upper plate 10 and the
lower plate 11 may be made of an electrically insulating material
such as polyvinyl chloride resin, polyamide resin, polyacetal
resin, and polyethylene resin. The support pillar 12 may be made of
a metal such as stainless steel and titanium, or plastic. The upper
plate 10 and the lower plate 11 may be fixed to the support pillars
12 by the aid of screws (not shown) respectively. A stainless screw
13a, which serves as the cathode 8, is provided at a central
portion of the upper plate 10 so that the stainless screw 13a
penetrates through the upper plate 10. The stainless screw 13a
fixes a first end 7a of a spring 7 made of stainless steel at the
lower surface of the upper plate 10. Similarly, a stainless screw
13b is provided at a central portion of the lower plate 11 so that
the stainless screw 13b penetrates through the lower plate 11 to
protrude from the upper surface of the lower plate 11. A clip 15
made of plastic is fixed to the screw 13b. As described above,
circular holes 14 for air nozzles are bored at four positions
through the lower plate 11. A first end of the wire member 9 is
hooked by a second end 7b of the spring 7 made of stainless steel.
A second end of the wire member 9 is grasped by the clip 15 while
stretching the wire member 9 and extending the spring 7. When the
wire member 9 is attached to the support jig 5 as described above,
the wire member 9 is supported in the electroforming bath 50 in a
state of being straightly stretched in the vertical direction.
[0066] The support jig 5 shown in FIG. 3 is a jig for performing
the electroforming of the one-core type ferrule. When a two-core
type ferrule is electroformed, for example, it is possible to use a
support jig 5' having a structure as shown in FIG. 4. The support
jig 5' shown in FIG. 4 includes auxiliary members 17 made of
plastic which are provided at two positions between an upper plate
10 and a lower plate 11. A wire-holding member 18 made of plastic,
which has pores 19 bored therethrough at two positions, is embedded
in a central portion of the auxiliary member 17. Stainless screws
13 and clips 15 are provided at two positions respectively. In
order to maintain the predetermined spacing distance and the
parallelism of the two wire members 9, solder members 25 for
integrating the wire members 9 while being separated from each
other by predetermined distances are provided on the wire members 9
supported between the auxiliary members 17. The support jig 5' has
the same structure as that of the support jig 5 shown in FIG. 3
except for the structure as specified above.
[0067] In the case of the ferrule having three or more cores, the
wire-holding member 18 may be modified depending on the number of
wires in the same manner as in the support jig 5' shown in FIG. 4,
and the numbers of the stainless screws 13 and the clips 15 may be
increased. However, the method for holding the wire member 9 is not
limited to the method described above. For example, an elastic
member such as rubber may be used other than the spring, or a
weight may be attached to the lower end of the wire, in the method
for stretching the wire. In order to control the spacing distance
between the two wire members more accurately, it is preferable to
use a support jig which will be explained in the fourth embodiment
described later on.
[0068] In the case of the ferrule having two or more cores, the
high dimensional accuracy is required as described above.
Therefore, the cross section of the wire member 9 is not limited to
the circular configuration. For example, it is also preferable to
use wire materials having cross-sectional configurations other than
the circular configuration as shown in (A)-(G) of FIG. 5. (A) shows
a wire for producing a two-core type ferrule, having an elliptic
configuration. Phantom lines in the drawing correspond to optical
fibers which are allowed to pass through the inside of the ferrule
to be obtained by the electroforming with the wire member.
[0069] (B) of FIG. 5 shows a sectional view of a wire member for
producing a three-core type ferrule, having a triangular
cross-sectional configuration with rounded corners. (C) of FIG. 5
shows a sectional view of a wire member for producing a four-core
type ferrule, having a quadrilateral cross-sectional configuration
with rounded corners. (D) of FIG. 5 shows a sectional view of a
wire member for producing a five-core type ferrule, having a
pentagonal cross-sectional configuration with rounded corners. (E)
of FIG. 5 shows a sectional view of a wire member for producing a
six-core type ferrule, having a hexagonal cross-sectional
configuration with rounded corners. (F) of FIG. 5 shows a sectional
view of a wire member for producing a seven-core type ferrule,
having a heptagonal cross-sectional configuration with rounded
corners. (G) of FIG. 5 shows a sectional view of a wire member for
producing a four-core type ferrule, having an oblong
cross-sectional configuration. In (G) of FIG. 5, it is assumed that
optical fibers indicated by phantom lines are arranged mutually
adjacently at the inside of the obtained ferrule. The wires shown
in (A)-(G) of FIG. 5 may have a shape without any rounded corners.
The wires may be used in place of the wire member 9 shown in FIGS.
1 to 4.
[0070] Returning to FIG. 2, the air blow nozzles 6 discharge a
small amount of air from their holes to agitate the electroforming
solution 3. However, the agitation of the electroforming solution 3
is not limited to the method based on air, for which it is possible
to adopt other techniques based on, for example, propeller,
ultrasonic wave, and ultra-vibration. Especially, it is desirable
to use the ultrasonic wave agitation in view of the maintenance of
the linearity of the wire member 9.
[0071] Those appropriately selected and used for the wire member 9
include, for example, metal wires made of iron or alloy thereof,
aluminum or alloy thereof, and copper or alloy thereof, those
plated with thin solder on such metal wires, and plastic wires made
of nylon, polyester, Teflon or the like. Among them, in the case of
the plastic wire, it is necessary to apply electroless plating
based on, for example, nickel or silver, in order to give
conductivity to the surface. It is advantageous to use conductive
plastic. In this case, when the electric power is applied to the
conductive plastic to heat it after the electroforming, the
extracting mold release is easily performed for the electroformed
product. The wire member 9 determines the inner diameter of the
ferrule obtained by the electroforming. Therefore, the high
accuracy is required for the thickness, the roundness, and the
linearity of the wire. The adjustment may be carried out for the
thickness, the roundness, and the linearity of the wire by means
of, for example, the method based on the extrusion with a die or
the wire drawing, or the centerless processing. At present, in the
case of a stainless wire having a diameter of 125 .mu.m, for
example, a stainless wire member product, which is in an error
range of about .+-.0.5 .mu.m, is available. In the case of the
wires of the multiple-core type having the cross-sectional
configurations other than the circular configuration as shown in
FIG. 5, it is possible to obtain an accurate dimension by means of,
for example, the extrusion based on a die.
[0072] Next, explanation will be made for the operation for forming
the tubular member by means of the electroforming with the
electroforming apparatus 100 shown in FIG. 2. The electroforming
bath 50 is charged with the electroforming solution 3, and then a
DC voltage is applied to the anodes 4 and the cathode 8 so that the
current density is about 4 to 20 A/dm.sup.2. When the
electroforming is performed for about 1 day at the current density
described above, an electroformed product having a thickness of a
diameter of 3 mm is allowed to grow around the wire member 9. After
completion of the electroforming, the support jig 5 is taken out of
the bath 50, and the wire member 9 is removed from the support jig
5. The wire member 9 can be removed, for example, by extracting it
from the electroformed product, or by dissolving it with a heated
acidic or alkaline aqueous solution. In the case of a metal wire
with solder plating, the metal wire may be extracted while heating
it.
[0073] Alternatively, the wire member 9 can be also taken out of
the electroformed product by means of extrusion. For example, a
cemented carbide pin 22 and a guide 21 having a through-hole 21a
formed therein as shown in FIG. 6 are used to arrange the guide 21
with respect to the electroformed product 23 so that the
through-holes 21a, 23a of them are coupled to one another with the
cemented carbide pin 22 penetrating therethrough. Thus, the wire
member 9 can be also extruded from the electroformed product 23
with the cemented carbide pin 22. It is desirable that this
procedure is carried out after the end of the wire member 9 of the
electroformed product 23 is slightly dissolved with a chemical
agent.
[0074] The procedure, in which the wire member 9 existing at the
center of the electroformed product is extracted, extruded, or
dissolved with the chemical agent, may be determined depending on
the selected material of the wire member 9. In general, when the
wire member is difficult to be dissolved in the chemical agent, and
it has a large tensile strength, then the extraction or extrusion
procedure is preferably utilized. When the wire member is easily
dissolved in the chemical agent, the dissolving procedure is
preferably adopted. For example, when the wire member is made of
iron or alloy thereof, the following procedure is available. That
is, after the wire member 9 is subjected to the mold release
treatment, the electroforming is carried out as described above
while covering parts of the wire with the electrically insulating
member 20 such as vinyl tape as shown in FIG. 7. When the
electrically insulating member 20 is peeled off from the
electroformed product to expose the wire member 9 as shown in FIG.
8, it is easy to extract the wire member 9 from the electroformed
product 23. In the case of the metal wire applied with solder
plating and the plastic wire applied with electroless plating, the
wire may be extracted in the same manner as described above without
performing the mold release treatment. In the case of the metal
wire applied with solder plating, the wire may be extracted while
being heated. When the extracting method is used, the wire member 9
is especially desirably a stainless wire as an alloy of iron.
Experimentally, the extracting procedure was successfully performed
for a stainless wire having a diameter of 0.126 mm having a length
up to about 100 mm.
[0075] When the wire member 9 is made of, for example, aluminum or
alloy thereof, or copper or alloy thereof, it is effective to
perform the removal by means of dissolution, because the wire
member 9 is easily dissolved in an acidic or alkaline aqueous
solution. It is preferable to use a strongly alkaline aqueous
solution as the dissolving solution which dissolves aluminum or
alloy thereof and which scarcely affects the electroformed metal.
Specifically, the wire can be easily dissolved and removed by
effecting heating to about 100.+-.3.degree. C. by using a strongly
alkaline aqueous solution composed of, for example, sodium
hydroxide or potassium hydroxide at a concentration of about 5 to
10 w/v %. Experimentally, an aluminum wire having a length of 10 mm
was successfully dissolved and removed in about 90 minutes. In this
case, it is unnecessary to perform the extraction. Therefore, it is
unnecessary to perform the electroforming by covering the wire with
the electrically insulating member as shown in FIG. 7. It is enough
to perform the electroforming for the entire surface of the wire
member 9. Further, it is unnecessary to perform the mold release
treatment for the wire member 9.
[0076] The obtained electroformed product can be used as a ferrule
after cutting the product into those having a predetermined length,
for example, with a thin blade cutter. Especially, when the method
of the present invention is used, the dimensional accuracy of the
inner diameter of the ferrule is extremely high. The accuracy is
determined by the dimensional error of the wire member 9 described
above. In order to enhance the roundness of the outer diameter of
the ferrule, it is preferable to perform finish machining for the
outer circumferential portion. The finish machining for the outer
circumferential portion may be performed such that the outer
circumference is subjected to cutting by means of NC machining.
When the wire member 9 is removed by means of the dissolving
method, the following procedure is available. That is, after
performing the electroforming, the linear electroformed product is
cut into those having a desired length. After that, the wire member
9 is completely dissolved in the acidic or alkaline solution to
form the through-hole at the inside of the electroformed product.
Subsequently, the outer circumference can be finished by means of,
for example, NC machining. In this case, the dissolving step may be
carried out after the outer circumference is subjected to the
machining.
[0077] The obtained ferrule may be fitted to a ferrule holder in
order that the rotational direction of the ferrule is positionally
determined, and the ferrule is accommodated in an optical fiber
connector housing. In order to connect the optical fibers with the
optical fiber connector based on the use of the ferrule, it is
desirable to use the PC connection of the optical fibers with each
other as described above. In order to perform the PC connection,
the end surface of the ferrule is machined into a convex spherical
surface or an inclined convex spherical surface, in a form in which
the optical fiber is inserted into the ferrule. The machining can
be carried out with an end surface grinder. The ferrule of the
present invention is a ferrule made of metal formed by the
electroforming. Therefore, the ferrule is advantageous in that the
PC polishing operation can be performed easier as compared with
conventional ferrules made of zirconia or glass. Further, it has
been revealed that the height of the optical fiber tip after the PC
polishing is approximately the same as that of the polished surface
of the ferrule. Therefore, the optical fiber can be connected
extremely accurately by using the ferrule of the present invention
and the optical fiber connector containing the same. Accordingly,
it is possible to realize the connection at low reflection
loss.
[0078] First Embodiment
[0079] An aluminum alloy wire (alloy of copper, magnesium, and
aluminum) of .phi.=0.126 mm having a circular cross section was
prepared. The wire was set to the jig 5 in a state of being
stretched in the vertical direction by means of the elasticity of
the spring 7 as shown in (A) of FIG. 3. The surface of the alloy
wire was degreased by sufficiently wiping the surface of the alloy
wire with gauze immersed with petroleum benzine. An electroforming
solution 3 containing a major component of nickel sulfamate was
charged in the electroforming bath 50 shown in FIG. 2. The four
anodes 4, which were composed of nickel balls placed in a net made
of titanium enclosed in a polyester bag, were installed at the four
corners of the base 52 around the center of the wire member 9. The
electroforming bath was heated to obtain a temperature of
55.+-.5.degree. C. while performing high speed filtration at a
filtration accuracy of 1 .mu.m. The jig 5 attached with the
aluminum alloy wire was washed well with water, and then it was
installed as shown in FIG. 2.
[0080] A DC voltage was applied to the cathode 8 and the nickel
anodes 4 to give a current density of about 4 to 20 A/dm.sup.2. The
electroforming was carried out for 1 day under the condition as
described above to obtain a nickel electroformed product having a
thickness of .phi.=about 3 mm. The electroformed product was taken
out of the bath, and it was washed. After that, the electroformed
product was cut into those having a length of 8.50 mm with an NC
automatic machining machine. The cut electroformed product was
immersed for 3 hours in a 20% sodium hydroxide aqueous solution
heated to 100.+-.3.degree. C. to completely dissolve and remove the
aluminum alloy wire. Thus, the electroformed product having a
tubular configuration was obtained. Subsequently, the electroformed
product was well washed with water by applying ultrasonic wave,
followed by being dried. After that, the electroformed product was
machined with the NC automatic machining machine to have a
thickness (outer diameter) of 2.00 mm and a length of 8.00 mm.
Thus, a finished product was obtained. The inner diameter was 0.126
mm.+-.0.5 .mu.m along the axial direction, although no machining
was performed at all after the electroforming. This fact means that
the inner diameter dimensional error is determined by the error of
the wire member (0.126 mm.+-.0.5 .mu.m) when the method of the
present invention is used, i.e., the ferrule having high accuracy
can be produced with ease when an available highly accurate wire
member is used.
[0081] Second Embodiment
[0082] A wire member 9 composed of SUS 304 of .phi.=0.126 mm having
a circular cross section was prepared, and the wire member 9 was
set to the jig 5 in the same manner as in the first embodiment. As
shown in FIG. 7, the wire member 9 was covered with a vinyl
adhesive tape 20 at intervals of 40 mm. The jig 5 was washed with
water, and then it was degreased and washed with water. After that,
a mold release treatment was applied by immersing the wire member 9
at room temperature for 10 minutes in an aqueous solution of a
mixture of commercially available Nikkanon Tack A, B produced by
Nihon Kagaku Sangyo Co., Ltd. Subsequently, the wire member 9 was
sufficiently washed with water, and then the electroforming was
performed at 9 A/dm.sup.2 for one day in the same manner as in the
first embodiment to obtain a nickel electroformed product having a
thickness of .phi.=about 3 mm in average. The electroformed product
was set to an extracting jig 24 formed with a through-hole 24a as
shown in FIG. 9. The wire member 9 was grasped by pincers to pull
it, and it was extracted from the electroformed product 23. The
electroformed product had a thickness of .phi.=about 3 mm and a
length of about 40 mm with a pore (inner hole) of .phi.=0.126 mm
formed at the axial center. The outer circumference of the
electroformed product was subjected to cutting with a compact NC
automatic machining machine about the center of the pore to obtain
a finished product having a thickness of 2.00 mm and a length of
8.00 mm. The error of the inner diameter dimension was 0.126
mm.+-.0.5 .mu.m in the axial direction, although no machining was
applied at all after the electroforming, in the same manner as in
the first embodiment.
[0083] Third Embodiment
[0084] An aluminum alloy wire having an elliptic cross section as
shown in (A) of FIG. 5 was prepared. The aluminum alloy wire was an
oval having a cross section with a minor axis of 0.126 mm and a
major axis of 0.252 mm. The electroforming was performed with the
aluminum alloy wire in the same manner as explained in the first
embodiment. As a result, a two-core type ferrule was successfully
obtained.
[0085] Fourth Embodiment
[0086] This embodiment is illustrative of a case of the production
of a two-core type ferrule as shown in (B) of FIG. 1, especially a
ferrule including two pores which are separated from each other by
a partition wall in the ferrule.
[0087] A support jig 60 shown in FIG. 10 is a jig to be used in the
electroforming bath in order to produce the two-core type ferrule
as described above. The jig 60 has a pair of reference pins 64a,
64b for adjusting the spacing distance between the wire members 90,
the reference pins 64a, 64b being embedded at mutually opposing
positions on a base plate 62 made of plastic. Each of the reference
pins 64a, 64b is a columnar pin made of stainless steel having a
diameter of 500 .mu.m, and each of them is embedded in the base
plate surface to make protrusion at a height of 5 to 10 mm from the
base plate surface. Guide pins 66 to 66e made of tungsten, which
are used to guide the wire member 90 and remove any slack of the
wire member 90, are provided on the base plate 62. The guide pins
66a to 66c maintain the tension of the wire member 90 disposed on
the side of the reference pin 64a, and the guide pins 66d, 66e
maintain the tension of the wire member 90 disposed on the side of
the reference pin 64b. A hook holder 68 made of metal is provided
at the lower end of the base plate 62. An opening 62a is formed at
a central portion of the base plate 62 in order to avoid the
anisotropy of the electrodeposition.
[0088] The wire member 90 is a wire made of aluminum alloy of
.phi.=0.126 mm having a circular cross section. As shown in FIG.
11, rings 90a, 90b are formed at both ends of the wire member 90.
The wire 90 is supported by the support jig 60 as follows. The
first end 90a of the wire 90 is arranged at the upper end of the
base plate 62. The wire 90 is allowed to extend successively along
the guide pins 66c, 66b. The wire 90 partially circumscribes the
reference pin 64a in the counterclockwise rotational direction, and
then it is directed downwardly. Subsequently, the wire 90 partially
circumscribes the lower reference pin 64b in the counterclockwise
rotational direction, and then it partially circumscribes the guide
pin 66d. The wire 90 passes through a hook 70 as described later
on, and it partially circumscribes the guide pin 66d in the
clockwise direction. Subsequently, the wire 90 partially
circumscribes the lower reference pin 64b again in the
counterclockwise direction, and then it is directed upwardly. The
wire 90 partially circumscribes the upper reference pin 64a in the
counterclockwise direction, and then it partially circumscribes the
guide pin 66a to arrive at the upper end of the base plate 62. The
both ends 90a, 90b of the wire are connected to one another on the
guide pin 66c.
[0089] The wire 90 is pressed against the surface of the base plate
62 by the aid of a holding plate 72 between the reference pin 64a
and the opening 62a. The wire 90 is hooked, under the guide pins
66d, 66e, by a first engaging section 70a of the hook 70 which has
a shape as shown in (A) and (B) of FIG. 12. A second engaging
section 70b of the hook 70 is hooked by an end of a hook holder 68.
As described above, the tension is maintained for the first part
90a and the second part 90b of the wire 90 by the aid of the guide
pins 66a to 66e, the reference pins 64a, 64b, and the hook 70. The
spacing distance between the first part 90a and the second part 90b
of the wire 90 stretched in parallel to one another over the
opening of the base plate 62 is adjusted by the reference pins 64a,
64b. The spacing distance between the first part 90a and the second
part 90b of the wire 90 can be easily changed by replacing the
reference pins 64a, 64b with other pins having a different
diameter. That is, when it is intended to produce a two-core type
ferrule having a spacing distance of 300 .mu.m based on the outer
diameter of the through-hole, it is preferable to use reference
pins 60a, 60b of .phi.=300 .mu.m.
[0090] The support jig 60 shown in FIG. 10 was installed in the
electroforming bath 50 shown in FIG. 2 in place of the support jig
5. In this procedure, the lower end of the base plate 62 of the
support jig 60 was fixed on the base 52, and the upper end of the
base plate 62 was supported at a position over the bath 50. The
electroforming solution 3 was charged until it arrived at a height
corresponding to the holding plate 72 of the support jig 60. The
electroforming solution 3 and the electroforming apparatus 100 were
constructed in the same manner as in the first embodiment except
for the support jig 5.
[0091] A DC voltage was applied to the cathode 8 and the nickel
anodes 4 to give a current density of about 4 to 20 A/dm.sup.2. The
electroforming was carried out for 1 day under the condition as
described above to obtain a nickel electroformed product having an
elliptic cross section with a minor axis of about 1800 .mu.m and a
major axis of about 2100 mm. The electroformed product was taken
out of the bath 50, and it was washed. After that, the
electroformed product was cut into those having a length of 8.50 mm
by using an NC automatic machining machine. The cut electroformed
product was immersed for 3 hours in a 20% sodium hydroxide aqueous
solution heated to 100.+-.3.degree. C. to completely dissolve and
remove the aluminum alloy wire. Thus, a tubular electroformed
product was obtained. FIG. 13 shows a sectional view of the
obtained electroformed product. As shown in FIG. 13, the
electroformed product 95 having an elliptic cross section had
through-holes 95a, 95b having an inner diameter of 125 .mu.m formed
at the inside while being separated from each other by a spacing
distance of 500 .mu.m.
[0092] Subsequently, the electroformed product 95 was sufficiently
washed with water by means of ultrasonic wave, followed by being
dried. After that, the outer circumferential portion was subjected
to cutting by using the NC automatic machining machine to process
the product to have a perfect circular configuration of an outer
diameter of 2000 .mu.m. The product was machined to have a length
of 8.00 mm. The inner diameter dimension of the through-holes 95a,
95b of the electroformed product 95 was 0.126 mm.+-.0.5 .mu.m along
the axial direction, although no machining was applied at all after
the electroforming. This fact means that the inner diameter
dimensional error is determined by the error of the wire member
(0.126 mm.+-.0.5 .mu.m) in the same manner as in the one-core type
ferrule obtained in the first embodiment, i.e., the two-core type
ferrule having high accuracy can be produced with ease when an
available highly accurate wire member is used.
[0093] Fifth Embodiment
[0094] In this embodiment, the electroforming was carried out by
using the same electroforming condition and the same electroforming
apparatus as those used in the fourth embodiment except that a wire
composed of SUS 304 of .phi.=0.126 mm having a circular cross
section was used as the wire 90.
[0095] The wires of the obtained electroformed product were set to
a jig which resembled the extracting jig shown in FIG. 9 but which
had two through-holes. The pair of wires were grasped by pincers
respectively to pull them, and they were extracted from the
electroformed product. As shown in FIG. 13, the electroformed
product had through-holes 95a, 95b having an inner diameter of 125
.mu.m at the inside, the through-holes 95a, 95b being separated
from each other by a spacing distance of 500 .mu.m. Subsequently,
the electroformed product was sufficiently washed with water by
applying ultrasonic wave, followed by being dried. After that, an
NC automatic machining machine was used to cut the outer
circumferential portion, and the product was processed into a
perfect circle having an outer diameter of 2000 .mu.m. The product
was processed to have a length of 8.00 mm. The inner diameter
dimension of the through-holes 95a, 95b of the electroformed
product 95 was 0.126 mm.+-.0.5 .mu.m in the axial direction,
although no machining was applied at all after the
electroforming.
[0096] Sixth Embodiment
[0097] The fourth and fifth embodiments are illustrative of the
exemplary production of the two-core type ferrule. However,
ferrules having three or more cores can be produced by improving
the apparatus shown in FIG. 10. For example, as shown in FIG. 14,
reference pins 98a to 98d are used in place of the reference pins
62a, 62b of the support jig shown in FIG. 10. Further, auxiliary
guide pins 102, 104a, 104b are used. In this embodiment, it is
unnecessary to use the guide pins 66d, 66e. When the pins are
arranged as described above, the spacing distance between wire
portions 90a, 90b of the wire 90 stretched via the pins is
determined by the outer diameter of the reference pins 98a, 98c.
The spacing distance between wire portions 90c, 90d is determined
by the outer diameter of the reference pins 98b, 98d. The spacing
distance between wire portions 90b, 90c is determined by the
spacing distance based on the outer diameter of the reference pins
98a, 98b and the spacing distance based on the outer diameter of
the reference pins 98c, 98d in consideration of the thickness of
the wire. When the electrodeposition is performed by using the jig
having the reference pins as shown in FIG. 14, a four-core type
ferrule is obtained, which has through-holes separated from each
other by predetermined spacing distances. The central positions of
the four through-holes formed in the ferrule are automatically
determined by the diameter and the embedded position of each of the
reference pins 98a to 98d of the support jig. Therefore, it is
possible to produce the ferrule including the optical fiber
through-holes which are formed and arranged extremely highly
accurately. The ferrule thus obtained may have, for example, a
cross-sectional structure as shown in FIG. 19 by appropriately
machine the contour after the electroforming.
[0098] The wire support structure shown in FIG. 14 is illustrative.
It is possible to provide a support jig which makes it possible to
form ferrules having five or more cores by means of the
electroforming highly accurately with ease by appropriately
increasing the number of reference pins.
[0099] Seventh Embodiment
[0100] This embodiment is illustrative of a case in which a sleeve
for a mechanical splice is constructed by using the ferrule made of
nickel produced in the first to third embodiments. The sleeve for
the mechanical splice is a sleeve for permanently connecting two
optical fibers. The sleeve can be formed, for example, by cutting
out the through-hole of the ferrule produced in the first
embodiment to have a tapered configuration, starting from both
sides toward the inside of the ferrule as shown in (A) of FIG. 15.
A slit 112 for releasing air when optical fibers are inserted from
the both sides can be provided at a central portion in the
longitudinal direction of the ferrule 110. The machining as
described above is performed extremely easily, because the ferrule
of the present invention is the ferrule made of metal obtained by
the electroforming.
[0101] The sleeve (ferrule 110) thus obtained can be used as shown
in (B) of FIG. 15 such that two optical fibers 40a, 40b are
inserted into tapered holes 110a, 110b at the both ends of the
sleeve, and they are connected at the central portion of the sleeve
110. The optical fibers 40a, 40b can be reliably fixed in the
ferrule by forcibly inserting the optical fibers 40a, 40b, because
the ferrule 110 of the present invention is made of metal.
Therefore, it is unnecessary to make adhesion by using any
adhesive. The optical fibers 40a, 40b can be fixed by means of
welding, because the ferrule is made of metal.
[0102] Eighth Embodiment
[0103] This embodiment is illustrative of a case in which an
optical fiber connector (connector plug) accommodating the ferrule
produced in the first to third embodiments is constructed with
reference to FIG. 16.
[0104] FIG. 16 shows an example of the optical fiber connector
structure having been previously subjected to the PC polishing. The
optical fiber connector 115 comprises a ferrule 92, a ferrule
holder 106 for holding the ferrule so that the rotational position
of the ferrule is determined, and a housing 108 for accommodating
the above components to function as a plug. The ferrule made of
nickel produced in the first embodiment was used as the ferrule 92.
The through-hole is widened to form a tapered configuration at the
rear end 94 of the ferrule 92 so that the optical fiber is easily
inserted. The ferrule holder 106 has a through-hole 106 formed in a
coaxial configuration having a diameter, for example, of 0.9 mm
which is larger than the rear end 92b of the ferrule 92. The
optical fiber is inserted into the through-hole together with its
coated portion 400.
[0105] A connecting optical fiber 40c, which is shorter than the
entire length of the ferrule 92, has been already inserted into the
tip of the ferrule 92. The tip 93 of the ferrule 92 is previously
applied with the PC polishing to have a convex spherical
configuration together with the end of the optical fiber 40c. The
PC polishing was performed with an end surface grinder. The ferrule
92 was polished by means of the PC polishing extremely easily and
highly accurately, because the ferrule 92 was made of nickel.
[0106] As described above, the optical fiber, which is shorter than
the entire length of the ferrule 92, is previously inserted into
the optical fiber connector 115, and the PC polishing is applied
beforehand before shipping. Accordingly, it is possible to omit the
PC polishing operation at any connection job site. At the
connection job site, the optical fiber 40a is inserted into the
opening 106a formed in the ferrule holder 106. The optical fiber
40a is connected to the optical fiber 40c at a fiber connection
point pp in the ferrule 92. The optical fiber connector 115
constructed at the job site as described above is coupled to
another optical fiber connector jack, a connector section of an
optical device, or an adapter for the optical fiber connector.
[0107] The mechanical strength of the ferrule of the present
invention is higher than those of conventional ferrules made of
ceramic or glass, because the ferrule of the present invention is
made of metal. The ferrule of the present invention improves the
durability concerning repeated PC junction and the durability of
the connector itself.
[0108] Ninth Embodiment
[0109] This embodiment illustrates the connection between the
optical fiber connector (connector plug) having the structure as
shown in the eighth embodiment and another optical fiber
connector.
[0110] FIG. 17 shows a situation in which the optical fiber
connector 115a (herein referred to as "connector plug") described
in the eighth embodiment is connected to an optical fiber connector
jack 130 to be coupled to the connector plug 115a. An optical fiber
40a has been already introduced into the connector plug 115a, and
subjected to the PC polishing at the tip of the ferrule 92a. The
connector jack 130 comprises an adapter 140 and the connector plug
115b. The adapter 140 and the connector plug 115b are detachably
coupled to one another by engaging an engaging hook 132b of the
adapter 140 with an engaging section 134b formed on a housing 108b
of the connector plug 115b. The connector plug 115b has the same
structure as that of the connector plug 115a. The tip of the
ferrule 92b is subjected to the PC polishing to have a convex
spherical configuration together with the tip of the optical fiber
40b.
[0111] In order to couple the connector jack 130 to the connector
plug 115a, the engaging hook 132a of the adapter 140 attached to
the connector jack 130 is engaged with the engaging section 134a
formed on the housing 108a of the connector plug 115a. When the
connector jack 130 is coupled to the connector plug 115a, then the
ferrule 92a and the ferrule 92b are aligned coaxially by the aid of
an alignment sleeve 142 of the adapter 140, and their tips are
subjected to PC junction highly accurately. Accordingly, the light
is transmitted at low reflection loss via the PC junction from the
optical fiber 40a to the optical fiber 40b or in the direction
opposite to the above.
[0112] The optical fiber connector of this embodiment may be
recognized as any one of the combination of the two connector plugs
115a, 115b and the adapter 140 and the combination of the connector
plug 115a and the connector jack 130.
[0113] Tenth Embodiment
[0114] FIG. 18 shows an example of the structure of an optical
fiber connector-equipped optical cable (optical cable-equipped
optical fiber connector). As shown in FIG. 18, the optical fiber
connector-equipped optical cable 120 is constructed by connecting
the optical fiber connector 108 as shown in FIG. 16 to both ends of
the optical fiber cable 114. However, a single continuous optical
fiber 40a has been already introduced into each of the ferrules.
The optical cable 120 can be connected, for example, to another
optical cable or another optical fiber connector by the aid of the
adapter 140 as shown in FIG. 17.
[0115] Eleventh Embodiment
[0116] FIG. 20 shows another embodiment of the ferrule of the
present invention. A ferrule 150 shown in FIG. 20 is a columnar
ferrule made of nickel-cobalt alloy formed by the electroforming. A
pore 150a having a diameter of about 0.126 mm, through which an
optical fiber passes, penetrates through the center of the column.
The pore 150a is widened in a tapered configuration at one end, and
it continues to a hollow section 150b having a diameter of 0.9 mm.
The optical fiber 40a is inserted from the side of the hollow
section 150b of the ferrule 150. A coated portion 400 (for example,
.phi.=0.9 mm) of the optical fiber 40a is also inserted into the
hollow section 150b. That is, the ferrule 150 functions as the
ferrule 92 (92a, 92b) and the holder 106 (106a, 106b) shown in
FIGS. 16 and 17. In the case of the conventional ferrule, the
center of the pore is eccentric with respect to the outer
circumference. Therefore, the reflection loss has been prevented
from increase by rotating the holder so that the mutual positions
of the cores of the optical fibers are coincident. However, the
ferrule obtained by the electroforming of the present invention has
the extremely high dimensional accuracy of the inner diameter.
Therefore, it is possible to omit the holder. In other words, the
ferrule shown in FIG. 20 can be recognized as a holder-integrated
ferrule.
[0117] Accordingly, the ferrule having the structure as shown in
FIG. 20 can be accommodated in a connector housing without using
any holder. Therefore, the use of the ferrule having such a
structure makes it possible to further simplify the structure of
the optical fiber connector.
[0118] The ferrule having the structure as shown in FIG. 20 can be
produced by means of the electroforming with a wire member having a
shape corresponding to the pore 150a and the hollow section 150b,
i.e., a wire member coaxially having a small diameter section
corresponding to the pore 150a and a large diameter section
corresponding to the hollow section 150b. Alternatively, an
electroformed product having the pore 150a is formed by means of
the electroforming with a wire member having a diameter
corresponding to the pore 150a, and then the wire member is removed
to cut the electroformed product into those having an appropriate
size. Subsequently, one end of the obtained electroformed product
is machined to apply cutting so that the pore 150a is deformed to
have the shape of the hollow section 150b.
[0119] The present invention has been specifically explained above
in accordance with the embodiments. However, the embodiments are
merely exemplary, and improvements and modifications within a range
of being conceived by those skilled in the art are included in the
scope of the present invention. The embodiment described above is
illustrative of the optical fiber connector which accommodates the
one-core type ferrule. However, it is needless to say that the
optical fiber connector can be constructed by using the
multiple-core type ferrule as produced in the embodiments described
above.
[0120] Explanation has been made as exemplified by the case in
which the aluminum alloy and SUS are used as the material for the
ferrule. However, arbitrary materials may be used provided that the
electroforming can be performed with the materials. The optical
fiber connector includes arbitrary optical fiber connectors
accommodating the ferrule, including, for example, plug-type
connectors, jack-type connectors, combinations of them,
combinations of two plugs and an adapter, receptacles, and optical
fiber cable-equipped connectors.
[0121] The present invention is based on the use of the
electroforming method. Therefore, it is unnecessary to use any
special molding machine and any mold which are expensive and which
require durability. The ferrule can be easily produced with the
cheap and versatile electroforming apparatus.
[0122] In the present invention, it is unnecessary to fire the
molded product at a high temperature of 500 to 1200.degree. C. as
having been hitherto performed. It is sufficient to heat the
electroforming solution to about 60.degree. C. Therefore, the
present invention lies in the method for producing the ferrule in
which the energy cost is low, and the energy is saved.
[0123] In the present invention, the dimension transfer performance
is extremely excellent, because the electroforming method is used.
It is unnecessary to polish the electroformed product with the
grinder, and hence the manual operation is omitted. Therefore, the
defective ratio is decreased, and the productivity is improved.
Especially, the dimensional error of the inner diameter of the
obtained ferrule is determined by the dimensional accuracy of the
wire member used as the base material for the electroforming.
Accordingly, it is easy to manage the dimension of the product.
Therefore, unlike the conventional technique in which the holder
(capillary) for rotatably supporting the ferrule in the optical
fiber connector is used when the ferrule is accommodated in the
optical fiber connector, it is possible to omit the use of such a
holder by using the ferrule of the present invention. Thus, the
ferrule of the present invention makes it possible to simplify the
structure of the optical fiber connector.
[0124] In the case of the conventional method, it has been
extremely difficult to obtain the dimension by means of polishing
for those of the multiple-core type, giving the problem that those
having three or more cores are incapable of production. However,
such ferrules can be easily produced in accordance with the method
of the present invention substantially in the same manner as in the
one-core type ferrule.
[0125] When the electroforming apparatus equipped with the
supporting apparatus of the present invention is used, the
multiple-core type ferrule can be produced easily and accurately at
low cost.
[0126] The optical fiber connector of the present invention is
provided with the ferrule made of metal formed by the
electroforming. Therefore, it is easy to perform the PC polishing
or the flat polishing therefor, and thus the productivity is
excellent. Further, the PC polishing or the flat polishing can be
performed highly accurately, and hence the highly accurately
controlled connection can be made between the excellent ferrules.
Thus, it is possible to realize the optical fiber connector with
low reflection loss. Further, the ferrule made of metal is
excellent in mechanical strength. Therefore, the present invention
is also advantageous in that the durability of the PC junction and
the durability of the optical connector are improved.
* * * * *