U.S. patent application number 15/868249 was filed with the patent office on 2018-05-17 for optical connection component.
The applicant listed for this patent is Sumitomo Electric Industries, Ltd.. Invention is credited to Naoki Matsushita, Yuuichi Mitose, Tetsuya Nakanishi, Takashi Sasaki.
Application Number | 20180136409 15/868249 |
Document ID | / |
Family ID | 57984360 |
Filed Date | 2018-05-17 |
United States Patent
Application |
20180136409 |
Kind Code |
A1 |
Mitose; Yuuichi ; et
al. |
May 17, 2018 |
OPTICAL CONNECTION COMPONENT
Abstract
The present embodiment achieves effective height reduction of an
entire optical connection component constituted by a bent optical
fiber and a fiber fixing component. The fiber fixing component
includes a first portion and a second portion which constitute the
holding portion in a state of being arranged in a manner
interposing an installation plane in order to hold one of non-bent
sections positioned at both ends of a bent portion in a state where
the one of non-bent sections is arranged on the installation plane.
Total lengths of the first portion and the second portion are
different from each other, and effective height reduction of the
entire optical connection component can be achieved by arranging
the bent portion in a stepped portion formed by the total length
difference.
Inventors: |
Mitose; Yuuichi;
(Yokohama-shi, JP) ; Nakanishi; Tetsuya;
(Yokohama-shi, JP) ; Sasaki; Takashi;
(Yokohama-shi, JP) ; Matsushita; Naoki;
(Yokohami-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sumitomo Electric Industries, Ltd. |
Osaka-shi |
|
JP |
|
|
Family ID: |
57984360 |
Appl. No.: |
15/868249 |
Filed: |
January 11, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/072926 |
Aug 13, 2015 |
|
|
|
15868249 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/0365 20130101;
G02B 6/3636 20130101; G02B 6/4285 20130101; G02B 6/02395 20130101;
G02B 6/4478 20130101; G02B 6/3616 20130101; G02B 6/4249 20130101;
G02B 6/4403 20130101 |
International
Class: |
G02B 6/36 20060101
G02B006/36; G02B 6/036 20060101 G02B006/036; G02B 6/02 20060101
G02B006/02 |
Claims
1. An optical connection component comprising: a bent optical fiber
constituted by: a glass portion; and a resin coating provided on an
outer peripheral surface of the glass portion, the bent optical
fiber having an exposed section where a part of the resin coating
located on one end portion side of the bent optical fiber is
removed and the glass portion is exposed, the exposed section
includes a bent portion, a first non-bent section, and a second
non-bent section, the bent portion being bent in a state where
substantially no bending stress remains, the first non-bent section
locating at a distal end of the bent optical fiber, and the first
non-bent section and the second non-bent section interposing the
bent portion therebetween; and a fiber fixing component having a
holding portion housing the first non-bent section in a state where
the first non-bent section is arranged on an installation plane
while exposing the bent portion, the first non-bent section
extending to a position apart from an end surface of the glass
portion, wherein the fiber fixing component includes a first
portion and a second portion which constitute the holding portion
in a state of being arranged in a manner interposing the
installation plane, a length of the first portion along a
longitudinal direction of the holding portion is longer than a
length of the second portion along the longitudinal direction of
the holding portion, and the second non-bent section is arranged in
a space where the second portion is positioned with respect to the
installation plane.
2. The optical connection component according to claim 1, wherein
the first portion and the second portion are arranged such that a
part of a holding surface of the first portion to hold the first
non-bent section directly faces the space where the second non-bent
section is arranged.
3. The optical connection component according to claim 1, wherein
the first portion includes a V-groove substrate having a V-groove
to define a position of the first non-bent section on the
installation plane, and the second portion includes a lid to
define, in cooperation with the V-groove of the V-groove substrate,
a position of the first non-bent section along a direction
orthogonal to the installation plane.
4. The optical connection component according to claim 3, wherein
the lid has a corner portion defined by: a first lid surface facing
a surface of the V-groove substrate provided with the V-groove; and
a second lid surface which is continued from the first lid surface
and faces the space side where the exposed section is positioned,
the corner portion having a curvature larger than the curvature of
the bent portion on a plane including the first non-bent section
and orthogonal to the installation plane.
5. The optical connection component according to claim 4, wherein
an interval located in the exposed section and extending along the
installation plane from a position exposed from the holding portion
of the fiber fixing component to the bent portion is 50 [.mu.m] or
more and 1 [mm] or less.
6. The optical connection component according to claim 4, wherein
the corner portion has a curvature of 100 [l/mm] or less.
7. The optical connection component according to claim 1, wherein
at least a part of the fiber fixing component is made of a material
transmitting ultraviolet light.
8. The optical connection component according to claim 1, wherein
the glass portion includes a single mode optical fiber containing
SiO.sub.2 glass as a main component and guaranteeing single mode
transmission at 1.31 .mu.m, the single mode optical fiber includes
a core, a first cladding surrounding the core, a second cladding
surrounding the first cladding, and a third cladding surrounding
the second cladding, a relative refractive index difference
.DELTA.1 of the core relative to the third cladding, a relative
refractive index difference .DELTA.2 of the first cladding relative
to the third cladding, and a relative refractive index difference
.DELTA.3 of the second cladding relative to the third cladding
satisfy relations of: .DELTA.1>.DELTA.2>.DELTA.3 and
.DELTA.3<-0.5[%], and a product V3 of the relative refractive
index difference .DELTA.3 and a cross-sectional area S of the
second cladding is less than -200 [%.mu.m.sup.2].
9. The optical connection component according to claim 1, wherein
an interval extending along the installation plane to the second
non-bent section from a side surface farthest from the second
non-bent section out of side surfaces of the second portion is 5
[mm] or less on a plane including the first non-bent section and
orthogonal to the installation plane, the bent portion has a
curvature of 0.4 [l/mm] or more, and an excessive loss at the bent
portion defined by a sum of a bending loss and a leakage loss is
0.5 [dB] or less at a use wavelength.
10. The optical connection component according to claim 1, wherein
a total length of the first non-bent section housed in the holding
portion is 0.3 mm or more and 1.5 mm or less.
11. The optical connection component according to claim 1, further
comprising a potting resin covering a section located in the
exposed section and excluding the first non-bent section housed in
the holding portion.
12. The optical connection component according to claim 11, wherein
the potting resin has a minimum thickness of 60 .mu.m or more.
13. The optical connection component according to claim 11, wherein
the potting resin has a contour line defining an outer shape
thereof, the contour line including a curved portion having a
curvature of 5/3 [l/mm] or less on a plane including the first
non-bent section and orthogonal to the installation plane.
14. The optical connection component according to claim 5, wherein
the corner portion has a curvature of 100 [l/mm] or less.
15. The optical connection component according to claim 2, wherein
the first portion includes a V-groove substrate having a V-groove
to define a position of the first non-bent section on the
installation plane, and the second portion includes a lid to
define, in cooperation with the V-groove of the V-groove substrate,
a position of the first non-bent section along a direction
orthogonal to the installation plane.
16. The optical connection component according to claim 15, wherein
the lid has a corner portion defined by: a first lid surface facing
a surface of the V-groove substrate provided with the V-groove; and
a second lid surface which is continued from the first lid surface
and faces the space side where the exposed section is positioned,
the corner portion having a curvature larger than the curvature of
the bent portion on a plane including the first non-bent section
and orthogonal to the installation plane.
17. The optical connection component according to claim 16, wherein
an interval located in the exposed section and extending along the
installation plane from a position exposed from the holding portion
of the fiber fixing component to the bent portion is 50 [.mu.m] or
more and 1 [mm] or less.
18. The optical connection component according to claim 16, wherein
the corner portion has a curvature of 100 [l/mm] or less.
19. The optical connection component according to claim 17, wherein
the corner portion has a curvature of 100 [l/mm] or less.
20. The optical connection component according to claim 12, wherein
the potting resin has a contour line defining an outer shape
thereof, the contour line including a curved portion having a
curvature of 5/3 [l/mm] or less on a plane including the first
non-bent section and orthogonal to the installation plane.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation application of
PCT/JP2015/072926 filed on Aug. 13, 2015, the entire contents of
which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a manufacturing method for
an optical connection component including a bent optical fiber
obtained by partly bending an optical fiber made of silica-based
glass.
BACKGROUND ART
[0003] Due to miniaturization of an optical module, reducing a
height of an optical fiber used in the vicinity of the optical
module (suppressing a height from the substrate as for the optical
fiber having one end vertically connected to the optical module or
the like) is demanded. To reduce the height of the optical fiber,
it is necessary to form a bent portion in the optical fiber.
[0004] Patent Document 1 discloses an optical fiber component
constituted by an optical component body and an optical fiber and
having the optical fiber obliquely attached so as to form a certain
angle (preferably, 10.degree. or more) with respect to a center
line of the optical component body. The Patent Document 1 discloses
that: a steep bent portion may be generated in the optical fiber
due to oblique attachment of the optical fiber with respect to the
center line of the optical component body; there may be a problem
in which mechanical reliability of the optical fiber is
deteriorated by large distortion caused at the steep bent portion
of the optical fiber; and the distortion is removed by heating the
steep bent portion in order to secure the mechanical reliability of
the optical fiber. Additionally, the Patent Document 1 discloses
that discharging, a carbon dioxide gas laser, a gas burner, and the
like can be utilized as a heating unit to resolve the
distortion.
[0005] Patent Document 2 discloses an apparatus to bend an optical
fiber by continuously heating a certain range of the optical fiber
by using a non-contact heating unit while relatively moving the
optical fiber and the non-contact heating unit. Additionally, this
Patent Document 2 discloses that arc discharge is suitably used as
the non-contact heating unit.
CITATION LIST
Patent Literature
[0006] Patent Document 1: Japanese Patent Application Laid-Open No.
2004-325622 [0007] Patent Document 2: Japanese Patent No.
5226797
SUMMARY OF INVENTION
Technical Problem
[0008] The inventors found following problems as a result of
studying the above-described prior art. In other words, in a bent
optical fiber having one end portion formed with a bent portion, a
fiber fixing component is attached more on a distal end side of the
end portion than the bent portion is, and an optical connection
component is constituted by these bent optical fiber and fiber
fixing component. Therefore, connection between the bent optical
fiber and an optical module or the like is achieved by fixing the
fiber fixing component attached to the end portion of the bent
optical fiber to the optical module or the like.
[0009] Basically, height reduction of an optical fiber due to
high-density packaging of an optical module may not be sufficient
only forming a bent portion at an end portion of the optical fiber,
and such height reduction is to be achieved on the basis of a
structural and positional relation between a fiber fixing component
and a bent optical fiber which constitute an optical connection
component. However, above-described Patent Documents 1 and 2 do not
disclose anything about a structural and positional relation
between an obtained bent optical fiber and a fiber fixing component
to be attached to the bent optical fiber.
[0010] Furthermore, the bent optical fiber has a structure in which
mechanical strength is largely decreased at the bent portion formed
at the end portion thereof. In other words, an exposed section of a
glass portion of the optical fiber where resin coating has been
removed is heated in order to form a bent portion having a
predetermined curvature in a state where no bending stress remains,
and therefore, a surface of the bent portion becomes fragile. As
for this point, the above-described Patent Documents 1 and 2 do not
disclose anything about a specific structure to secure sufficient
mechanical strength of the bent optical fiber having the end
portion thereof attached with the fiber fixing component.
[0011] The present invention is made to solve the above-described
problems, and is directed to providing an optical connection
component having a structure in order to achieve effective height
reduction by appropriately setting a structural and positional
relation between a bent optical fiber and a fiber fixing component,
and furthermore, providing the optical connection component having
a structure in order to improve mechanical strength of the bent
optical fiber having an end portion thereof attached with the fiber
fixing component.
Solution to Problem
[0012] To solve the above problems, an optical connection component
according to the present embodiment includes a bent optical fiber
and a fiber fixing component attached to one end portion of the
bent optical fiber and adapted to fix a light input/output surface
located on the one end portion side of the bent optical fiber to an
optical module including an optical integrated circuit chip and the
like. The bent optical fiber is constituted by: a glass portion
extending along a predetermined axis; and a resin coating provided
on an outer peripheral surface of the glass portion, and
furthermore, a bent portion bent at a predetermined curvature in a
state where substantially no bending stress remains is formed in an
exposed section of the glass portion where a part of the resin
coating positioned on the one end portion side of the bent optical
fiber is removed. The fiber fixing component includes a holding
portion housing a first non-bent section in a state where the first
non-bent section is arranged on a predetermined installation plane
while exposing the bent portion, and the first non-bent section
extends to a position apart from an end surface of the glass
portion by a predetermined distance in the exposed section.
Particularly, the fiber fixing component includes a first portion
and a second portion which constitute the holding portion in a
state of being arranged in a manner interposing the installation
plane, and a length of the first portion along a longitudinal
direction of the holding portion is longer than a length of the
second portion along the longitudinal direction of the holding
portion. Additionally, in a state where the first non-bent section
is housed in the holding portion, the fiber fixing component is
fixed to the exposed section of the glass portion such that a
second non-bent section positioned on an opposite side of the first
non-bent section with respect to the bent portion is arranged in a
space where the second portion is positioned with respect to the
installation plane.
Advantageous Effects of Invention
[0013] According to the present embodiment, it is possible to
achieve effective height reduction of the entire optical connection
component constituted by the bent optical fiber and the fiber
fixing component. In other words, since a difference is provided
between the total lengths of the first portion and the second
portion which constitute the fiber fixing component, the bent
portion is arranged in a stepped portion formed by the total length
difference, and as a result, the effective height reduction of the
entire optical connection component can be achieved.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a view to describe a use state of an optical
connection component according to the present embodiment.
[0015] FIGS. 2A and 2B illustrate diagrams to describe an exemplary
structure and exemplary curvature distribution of a bent portion
and the vicinity thereof of a bent optical fiber applied to the
optical connection component according to the present
embodiment.
[0016] FIG. 3 is a view to describe an arrangement relation of main
constituent elements of the optical connection component according
to the present embodiment by using a Cartesian coordinate system
(XYZ coordinate system).
[0017] FIGS. 4A and 4B illustrate views to describe a first
exemplary structure and exemplary application of the optical
connection component according to the present embodiment.
[0018] FIGS. 5A to 5C illustrate diagrams to describe an exemplary
single mode optical fiber applicable to the optical connection
component according to the present embodiment.
[0019] FIG. 6 is a view to describe a second exemplary structure of
the optical connection component according to the present
embodiment.
[0020] FIGS. 7A and 7B illustrate views to describe a third
exemplary structure of the optical connection component according
to the present embodiment.
[0021] FIGS. 8A and 8B illustrate views of cross-sectional
structures respectively taken along lines X1-X1 and X2-X2
illustrated in FIGS. 7A and 7B of the third exemplary structure of
the optical connection component according to the present
embodiment.
[0022] FIG. 9 is a graph illustrating a relation between a minimum
curvature radius R.sub.min [mm] and displacement [mm] of the bent
optical fiber at the time of applying a predetermined tension in
the third exemplary structure of the optical connection component
according to the present embodiment.
DESCRIPTION OF EMBODIMENTS
Details of Embodiment of Present Invention
Description of Embodiment of Present Invention
[0023] First, respective aspects corresponding to the embodiment of
the present invention will be listed and described.
[0024] (1) As an aspect of the present embodiment, an optical
connection component includes a bent optical fiber and a fiber
connection component. The bent optical fiber is constituted by: a
glass portion extending along a predetermined axis; and resin
coating provided on an outer peripheral surface of the glass
portion. Additionally, in the bent optical fiber, a bent portion
bent at a predetermined curvature in a state where substantially no
bending stress remains is formed in an exposed section of the glass
portion where a part of the resin coating positioned on one end
portion side of the bent optical fiber is removed. The fiber fixing
component includes a holding portion housing a first non-bent
section in a state where the first non-bent section is arranged on
a predetermined installation plane while exposing the bent portion,
and the first non-bent section extends to a position apart from an
end surface of the glass portion by a predetermined distance in the
exposed section. Furthermore, the fiber fixing component includes a
first portion and a second portion which constitute the holding
portion in a state of being arranged in a manner interposing the
installation plane, and a length of the first portion along a
longitudinal direction of the holding portion is set longer than a
length of the second portion along the longitudinal direction of
the holding portion. In this structure, in a state where the first
non-bent section is housed in the holding portion, the fiber fixing
component is fixed to the exposed section of the glass portion such
that a second non-bent section positioned on an opposite side of
the first non-bent section with respect to the bent portion is
arranged in a space where the second portion is positioned with
respect to the installation plane. Additionally, as an aspect of
the present embodiment, the first portion and the second portion
are arranged such that a part of a holding surface of the first
portion to hold the first non-bent section directly faces the space
where the second non-bent section is arranged. With this structure,
the fiber fixing component has a stepped portion where the bent
portion is arranged.
[0025] (2) As an aspect of the present embodiment, the first
portion may include a V-groove substrate having a V-groove to
define a position of the first non-bent section on the installation
plane and arrange one or a plurality of bent optical fibers, and
the second portion may include a lid to define, in cooperation with
the V-groove of the V-groove substrate, the position of the first
non-bent section formed along a direction orthogonal to the
installation plane. As an aspect of the present embodiment, a
corner portion of the lid is shaped into a shape, preferably,
having a curvature larger than the curvature of the bent portion on
a plane including the first non-bent section and orthogonal to the
installation plane, and the corner portion of the lid is defined
by: a first lid surface facing a surface of the V-groove substrate
provided with the V-groove; and a second lid surface which is
continued from the first lid surface and faces the space side where
the exposed section of the glass portion is positioned. As an
aspect of the present embodiment, an interval located in the
exposed section of the glass portion and extending along the
installation plane from a position exposed from the holding portion
of the fiber fixing component to the bent portion is, preferably,
50 [.mu.m] or more and 1 [mm] or less. As an aspect of the present
embodiment, the shaped corner portion of the lid has the curvature
of, preferably, 100 [l/mm] or less. As an aspect of the present
embodiment, at least a part of the fiber fixing component is made
of, preferably, a material that transmits ultraviolet light.
[0026] (3) As an aspect of the present embodiment, the glass
portion may include a single mode optical fiber (hereinafter
referred to as SMF) that contains SiO.sub.2 glass as a main
component and guarantees single mode transmission at a use
wavelength. In this case, the SMF includes at least a core, a first
cladding surrounding the core, a second cladding surrounding the
first cladding, and a third cladding surrounding the second
cladding. Additionally, a relative refractive index difference
.DELTA.1 of the core relative to the third cladding, a relative
refractive index difference .DELTA.2 of the first cladding relative
to the third cladding, and a relative refractive index difference
.DELTA.3 of the second cladding relative to the third cladding
satisfy relations of .DELTA.1>.DELTA.2>.DELTA.3 and
.DELTA.3<-0.5 [%]. Additionally, the product V3 of the relative
refractive index difference .DELTA.3 and a cross-sectional area S
of the second cladding is less than -200 [%.mu.m.sup.2]. As an
aspect of the present embodiment, it is preferable that: an
interval extending along the installation plane to the second
non-bent section from a side surface farthest from the second
non-bent section out of side surfaces of the second portion is 5
[mm] or less on a plane including the first non-bent section and
orthogonal to the installation plane; the bent portion has a
curvature of 0.4 [l/mm] or more; and an excessive loss at the bent
portion defined by the sum of a bending loss and a leakage loss is
0.5 [dB] or less at the use wavelength. As an aspect of the present
embodiment, a total length of the first non-bent section housed in
the holding portion is, preferably, 0.3 mm or more and 1.5 mm or
less.
[0027] (4) As an aspect of the present embodiment, the optical
connection component may further include a potting resin covering a
section located in the exposed section of the glass portion and
excluding the first non-bent section housed in the holding portion.
As an aspect of the present embodiment, a minimum thickness of the
potting resin is, preferably, 60 .mu.m or more. As an aspect of the
present embodiment, on the plane including the first non-bent
section and orthogonal to the installation plane, a contour line
defining an outer shape of the potting resin includes, preferably,
a curved portion having a curvature of 5/3 [l/mm] or less, that is,
a curvature radius R of 0.6 [mm] or more.
[0028] Thus, the respective aspects listed in the above
"Description of Embodiment of Present Invention" can be applied to
all of remaining aspects or to any combinations of these remaining
aspects.
Details of Embodiment of Present Invention
[0029] In the following, a specific structure of an optical
connection component according to the present embodiment will be
described in detail with reference to the attached drawings. Note
that the present invention is not limited to examples herein and
intended to include all modifications within a scope recited in the
scope of claims and a meaning equivalent thereto.
[0030] FIG. 1 is a view to describe a use state of the optical
connection component according to the present embodiment, and FIG.
1 illustrates an electronic substrate 200 including an optical
integrated circuit chip and the like, a bent optical fiber 100
having one end portion formed with a bent portion BA subjected to
heat bending processing, a fiber fixing component 300 attached to
the one end portion of the bent optical fiber 100 formed with the
bent portion BA, a potting resin 400 provided in order to reinforce
and protect the bent portion BA in a state being supported by the
fiber fixing component 300, and a connector 250 provided in order
to optically connect the bent optical fiber 100 to an optical fiber
for interconnection wiring or a single mode optical fiber of an
external transmission channel (hereinafter referred to as SMF).
[0031] In the example of FIG. 1, the bent optical fiber 100 has a
glass fiber (bare fiber) 110 and resin coating 120 surrounding the
glass fiber 110, and the resin coating 120 is removed at the one
end portion formed with the bent portion BA. On the other hand, the
connector 250 is attached to the other end portion of the bent
optical fiber 100. Furthermore, since a light input/output end
surface of the bent optical fiber 100 is optically connected to the
optical integrated circuit chip and the like via the fiber fixing
component 300, mechanical strength at the connecting portion can be
improved. A bottom surface of the fiber fixing component 300 may be
inclined by about 8.degree. with respect to an installation surface
200a of the electronic substrate 200 in order to avoid increase of
a connection loss caused by reflection on the light input/output
end surface of the bent optical fiber 100. In other words, in the
example of FIG. 1, a Z-axis indicating a height direction of the
fiber fixing component 300 is inclined by about 8.degree. with
respect to the installation surface 200a of the electronic
substrate 200. Meanwhile, in a case where the bottom surface of the
fiber fixing component 300 is not inclined with respect to the
height direction (Z-axis direction), the installation surface of
the electronic substrate 200 is arranged at a position indicated by
a broken line 200b with respect to the Z-axis.
[0032] FIGS. 2A and 2B illustrate diagrams to describe an exemplary
structure and exemplary curvature distribution of the bent portion
and the vicinity thereof (an exposed section where the glass fiber
110 is exposed by removing the resin coating 120) of the bent
optical fiber 100 applied to the optical connection component
according to the present embodiment. Particularly, FIG. 2A is a
view illustrating an exemplary structure of an end portion of the
bent optical fiber 100 illustrated in FIG. 1, that is, the vicinity
of the bent portion BA formed on the end portion of the glass fiber
110 where the resin coating 120 is removed, and FIG. 2B is a
diagram illustrating exemplary curvature distribution of the bent
portion BA and the vicinity thereof.
[0033] In the present embodiment, as illustrated in FIGS. 2A and
2B, the bent portion BA and the vicinity thereof (end portion of
the bent optical fiber 100) are constituted by: a region A having a
curvature d of 0.1 [l/mm] or less (first non-bent section continued
to the bent portion BA); a region B having a curvature d of 0.4
[l/mm] or more (section corresponding to the bent portion BA and
applied with heat bending processing); and region C having a
curvature d of 0.1 [l/mm] or less (second non-bent section
continued to the bent portion BA). Here, as illustrated in FIG. 2A,
since the section applied with the heat bending processing (bent
portion BA) keeps a bent shape even without fixing both ends of the
section, no bending stress remains in this section. On the other
hand, in a section applied with non-heat bending processing, a bent
state cannot be kept without fixing both ends of the section, and
bending stress constantly remains in the section applied with the
non-heat bending processing while the bent state is kept.
[0034] Meanwhile, in FIG. 2A, R1 indicates a boundary between the
region A and the region B, and R2 indicates a boundary between the
region B and the region C, but these regions A to C are continuous
sections of the bent optical fiber 100. Additionally, in the
present specification, a "bent angle .theta." is defined by an
angle formed by two straight lines respectively extending along the
region A and the region C positioned on both sides of the region B
(bent portion BA) as illustrated in FIG. 2A.
[0035] A burner, a CO.sub.2 laser, arc discharge, a heater, or the
like can be used in the heat bending processing to be applied to
the region B corresponding to the bent portion BA. The CO.sub.2
laser has characteristics advantageous to perform precise control
for the curvature distribution because irradiation intensity, an
irradiation range, and an irradiation period can be easily
adjusted. Since the glass is opaque in the vicinity of a general
wavelength 10 [.mu.m] of the CO.sub.2 laser, it can be considered
that irradiation energy of the CO.sub.2 laser is absorbed by a
surface layer of the optical fiber and transmitted by re-radiation
and heat conduction. In a case where power of the CO.sub.2 laser is
too high, a surface temperature of the optical fiber is steeply
increased up to an evaporation temperature of the glass, and as a
result, a surface shape of the optical fiber cannot be maintained.
Therefore, irradiation power of the CO.sub.2 laser is appropriately
adjusted such that: the surface glass of the optical fiber does not
evaporate; and distortion is removed by continuously keeping a
fiber cross section of a heated portion to have a state where the
temperature is increased and held at a temperature of an operating
point or more for a predetermined period.
[0036] FIG. 3 is a view to describe an arrangement relation of main
constituent elements of the optical connection component according
to the present embodiment by using a Cartesian coordinate system
(XYZ coordinate system). FIG. 4A is a view to describe a first
exemplary structure of the optical connection component according
to the present embodiment, and FIG. 4B is a view to describe
exemplary application of the optical connection component according
to the present embodiment.
[0037] As illustrated in FIGS. 2A and 2B, the surface of the glass
fiber 110 (glass portion) is exposed at one end portion of the bent
optical fiber 100 by removing the resin coating 120. In this
exposed section, the region B (section corresponding to the bent
portion BA) bent at a predetermined curvature is formed in a state
where substantially no bending stress remains. Additionally, while
the fiber fixing component 300 has the structure exposing the
region B, the fiber fixing component 300 includes a holding portion
to house the region A located in the exposed section (first
non-bent section corresponding to the region A extending to a
position apart from the end surface of the glass fiber 110 by a
predetermined distance in FIG. 2A). Since the region A is housed in
the holding portion, the region A is in a state of being arranged
on an installation plane corresponding to a Y-Z plane in FIG. 3.
Meanwhile, as illustrated in FIG. 3, the fiber fixing component 300
includes a first portion and a second portion which constitute the
holding portion in a state of being arranged in a manner
interposing the installation plane. In the following description,
unless otherwise not particularly specified, the first portion
includes a V-groove substrate 310 having a holding surface 310a on
which a V-groove 311 to define a position of the region A on the
installation plane is formed, and the second portion includes a lid
320 to define, in cooperation with the V-groove 311 of the V-groove
substrate 310, the position of the region A along a direction
orthogonal to the installation plane. In the case where the fiber
fixing component 300 is thus constituted by the V-groove substrate
310 and the lid 320, the holding portion is constituted by: the
V-groove 311 formed on the holding surface 310a; and a surface of
the lid 320 facing the holding surface 310a.
[0038] Furthermore, in the example of FIG. 3, a length of the
V-groove substrate 310 along a longitudinal direction of the
holding portion (Z-axis direction illustrated in FIG. 3) is set
longer than a length of the lid 320 along the Z-axis direction.
Additionally, the V-groove substrate 310 and the lid 320 thus
having different lengths are arranged in a manner such that a part
of the holding surface 310a of the V-groove substrate 310 directly
faces a space where the region C positioned on an opposite side of
the region A with respect to the region B (second non-bent section
that interposes the bent portion BA in cooperation with the first
non-bent section) is arranged. As a result, a stepped portion that
defines a housing space of the region B is formed in the fiber
fixing component 300. In other words, when the fiber fixing
component 300 is fixed in the exposed section of the glass fiber
110, the region C positioned on the opposite side of the region A
with respect to the region B is arranged in a space where the lid
320 is positioned with respect to the installation plane while the
region A is in a state of being arranged in the V-groove 311. With
this structure, as illustrated in FIG. 4A, a height of the optical
connection component according to the present embodiment is reduced
by an amount D compared to a case where the bent portion BA is
arranged on the V-groove substrate 310 side (first portion side)
with respect to the installation plane (Y-Z plane).
[0039] Meanwhile, in the examples of FIGS. 3 and 4A, the fiber
fixing component 300 is constituted by two physically separated
members of the V-groove substrate 310 and the lid 320, but may also
be constituted by a single member. FIG. 4B is a view illustrating a
structure of a fiber fixing component 300A constituted by a single
member. In FIG. 4B, the fiber fixing component 300A includes a
through hole 312 as a holding portion to house an end portion of
the bent optical fiber 100, particularly, the first non-bent
section corresponding to the region A in the exposed section of the
glass fiber 110 where the resin coating 120 is removed.
Additionally, the fiber fixing component 300A is constituted by a
first portion 310A (portion corresponding to the above-described
V-groove substrate 310) and a second portion 320A (portion
corresponding to the above-described lid 320) which are arranged in
a manner interposing the installation surface (Y-Z plane) where the
through hole 312 is provided.
[0040] As illustrated in FIG. 4B, in a case of applying the fiber
fixing component 300A constituted by the single member including
the through hole 312, a ferrule having a structure categorized in a
single core connector such as an FC, an SC, and an LC, and a
multi-core connector such as an MPO and an MT can be applied as the
fiber fixing component 300A. To obtain a merit of height reduction,
an exposed region 310Aa is provided by removing a part of a normal
ferrule. On the other hand, as illustrated in FIGS. 3 and 4A, in a
case where the fiber fixing component 300 is constituted by the
V-groove substrate 310 and the lid 320, multi-component glass such
as Pyrex (registered trademark), a SiO.sub.2 substrate, or the like
can be applied as a material of the V-groove substrate 310.
However, as for the material of the V-groove substrate 310, it is
preferable to use a material that transmits UV light such that the
V-groove substrate can be bonded to an optical integrated circuit
by using a UV curing resin. Thus, since the fiber fixing component
300 is partly constituted by the material that transmits UV light,
bond fixing by the UV curing resin can be achieved, and production
efficiency of the optical connection component can be improved.
[0041] Next, the bent optical fiber 100 of the optical connection
component according to the present embodiment will be described
using FIGS. 5A to 5C. Since the bent portion BA having the large
curvature d is formed in the bent optical fiber 100, a multi-mode
optical fiber (hereinafter referred to as MMF) is generally
utilized, but in the following description, an SMF, particularly,
an example of a bend insensitive optical fiber (BIF, hereinafter
referred to as BI optical fiber) having a trench structure will be
described.
[0042] In other words, since it is also demanded to reduce a
connection loss with the SMF frequently applied to a transmission
channel installed in an optical fiber for interconnection wiring
such as the bent optical fiber 100 connected to the optical module
or the like, there is also enough room to study application of the
SMF, not limited to the MMF. Particularly, as the SMF for
interconnection wiring installed in a limited space, the BI optical
fiber having the trench structure can be expected to reduce a
bending loss while suppressing a cutoff wavelength from becoming
longer. Therefore, the inventors consider it technically
advantageous to apply the BI optical fiber as the bent optical
fiber to be inserted as a part of the interconnection wiring
between an electronic component in a base station and an external
transmission channel (SMF).
[0043] However, according to the findings of the inventors, a
photo-elastic effect by distortion is eliminated while no bending
stress remains in the obtained bent optical fiber itself in heat
bending processing disclosed in above-described Patent Documents 1
and 2. Therefore, as illustrated in FIG. 5C, an equivalent
refractive index in a bent state in a glass region constituting the
trench structure becomes higher than an equivalent refractive index
in a case of the non-heat bending processing (optical confinement
effect provided by the trench structure is reduced). Note that, in
FIG. 5C, P100 indicates distribution of an equivalent refractive
index of a BI optical fiber including a bent portion having a
curvature radius R=2 mm formed by the non-heat bending processing,
and P200 indicates distribution of an equivalent refractive index
of a BI optical fiber including a bent portion having a curvature
radius R=2 mm formed by the heat bending processing. In this case,
since the effect of the trench structure (optical confinement
effect) in the BI optical fiber is reduced, a bending loss is
increased. In other words, in a case of simply applying the SMF,
particularly, the BI optical fiber as the bent optical fiber
constituting a part of the interconnection wiring, an insertion
loss of the bent optical fiber constituted by the BI optical fiber
is significantly increased. Therefore, in the following, a
structure of the BI optical fiber having the trench structure
preliminarily considering elimination of the photo-elastic effect
will be described as an example in order that the SMF such as the
BI optical fiber can be applied to the bent optical fiber 100 of
the present embodiment.
[0044] FIG. 5A is a view illustrating a cross-sectional structure
of the BI optical fiber as an example of the SMF, FIG. 5B is
distribution of a refractive index of the BI optical fiber
illustrated in FIG. 5A, and FIG. 5C is distribution of an
equivalent refractive index of the BI optical fiber illustrated in
FIG. 5A in a state subjected to bending processing.
[0045] As illustrated in FIGS. 5A and 5B, the BI optical fiber
includes: a core 111 having a radius r1 and extending along a
predetermined axis (optical axis AX); first cladding 112 provided
on an outer peripheral surface of the core 111 and having a radius
r2; second cladding 113 provided on an outer peripheral surface of
the first cladding 112 and having a radius r3; and third cladding
114 provided on an outer peripheral surface of the second cladding
113 (region constituting the trench structure of the BI optical
fiber). Furthermore, a refractive index of the core 111 is n1, a
refractive index of the first cladding 112 is n2 (<n1), a
refractive index of the second cladding 113 is n3 (<n2), and a
refractive index of the third cladding 114 is n4 (<n1, >n3).
Furthermore, a relative refractive index difference .DELTA.1 of the
core 111 with respect to the third cladding 114, a relative
refractive index difference .DELTA.2 of the first cladding 112 with
respect to the third cladding 114, and a relative refractive index
difference .DELTA.3 of the second cladding 113 with respect to the
third cladding 114 satisfy relations of
.DELTA.1>.DELTA.2>.DELTA.3 and .DELTA.3<-0.5 [%].
Additionally, the product V3 of the relative refractive index
difference .DELTA.3 and a cross-sectional area S of the second
cladding (refractive index volume to define an optimal trench
structure) is set to less than -200 [%.mu.m.sup.2] in order to
effectively suppress increase of the bending loss caused by
elimination of the photo-elastic effect. In the bent optical fiber
100 achieved by forming the bent portion BA having the curvature d
of 0.4 [l/mm] or more at one end portion of the BI optical fiber
having the above-described structure, an excessive loss in the bent
portion BA defined by the sum of a bending loss and a leakage loss
is 0.5 [dB] or less at a use wavelength, for example, a wavelength
of 1.31 [.mu.m].
[0046] A relative refractive index difference (.DELTA.) of each
portion while setting the third cladding 114 as a reference is a
value determined by an equivalent step index (ESI). An outer
diameter of each of the first to third cladding 112, 113, and 114
is determined by utilizing a value obtained by determining a
position where a derivative value of radial change of the
refractive index becomes maximal near a boundary between cladding
and cladding.
[0047] Additionally, composition of the BI optical fiber having the
above-described structure is manufactured by appropriately adding
dopant for refractive index control to SiO.sub.2 glass. As an
example, the core 111 is made of SiO.sub.2 glass to which GeO.sub.2
is added, the first cladding 112 is made of pure SiO.sub.2 glass,
the second cladding 113 constituting the trench structure is made
of SiO.sub.2 glass to which fluorine is added, and the third
cladding 114 is made of pure SiO.sub.2 glass. Such glass
composition is excellent from the viewpoint of economy and shape
controllability. Note that Cl may also be added to the third
cladding 114. Additionally, GeO.sub.2 and fluorine may be co-doped
in the core 111.
[0048] It is desirable to have a transmission characteristic
equivalent to a general-purpose SMF compliant with the BI optical
fiber ITU-TG.652 (hereinafter referred to as SSMF) applied as the
bent optical fiber 100 of the optical connection component
according to the present embodiment, and connection to another SSMF
can be achieved economically with a low loss. In the BI optical
fiber having a low bending loss property, MPI generally tends to be
high because a bending loss in a high-order mode is low. Therefore,
in the present embodiment, a refractive index structure of the core
111 is set such that a cutoff wavelength .lamda.c measured at a
fiber length 22 m becomes 1260 [nm] or less. Consequently, a BI
optical fiber in which the MPI caused by interference with the
high-order mode is -30 dB or less can be achieved, and signal
quality required for a digital signal can be maintained.
Furthermore, in a case where an MFD at a wavelength of 1.31 [.mu.m]
is 8.6.+-.0.4 [.mu.m], connection to another SSMF can be achieved
with a low loss. Meanwhile, in a case where a fiber diameter (outer
diameter of the glass fiber 110) is formed small, distortion at the
time of bending the fiber becomes small. In this case, while a
housing property is improved, manufacture of a ferrule of an
optical connector becomes difficult in a case where a fiber shape
is too thin, and therefore, the BI optical fiber applicable to the
bent optical fiber 100 of the present embodiment has a glass outer
diameter of, preferably, 80 [.mu.] or more and 125 [.mu.m] or
less.
[0049] Meanwhile, in the structure as illustrated in FIG. 4A, when
tensile stress is applied to the bent optical fiber 100, stress
concentrates on the bent optical fiber 100 at a contact portion
with the fiber fixing component 300. For example, in the example of
FIG. 4A, in a case where the bent portion BA of the bent optical
fiber 100 is arranged on the V-groove substrate 310 side with
respect to the installation plane, stress concentrates on a portion
contacting the corner portion P1 of the V-groove substrate 310. On
the other hand, in a case where the bent portion BA of the bent
optical fiber 100 is arranged on the installation plane on the lid
320 side with respect to the installation plane, stress
concentrates on a portion contacting the corner portion P2 of the
lid.
[0050] Since the resin coating 120 at the end portion where the
bent portion BA is formed is removed, the bent optical fiber 100
has a structure in which mechanical strength in this exposed
section, particularly, the bent portion BA is significantly
lowered. Therefore, the present embodiment has a structure to
protect the vicinity of the bent portion BA. Specifically, the
optical connection component according to the present embodiment
includes various kinds of structures such as a first protection
structure that improves the structure of the fiber fixing component
300 itself and a second protection structure that protects the bent
portion BA with a potting resin in order to avoid: increase of an
insertion loss caused by stress concentration on the exposed
section of the bent optical fiber 100 contacting the corner
portions P1 and P2 of the fiber fixing component 300; and damage of
the bent optical fiber 100 itself.
[0051] FIG. 6 is a view to describe an example including the first
protection structure as a second exemplary structure of the optical
connection component according to the present embodiment.
[0052] The corner portion P2 of the lid 320 illustrated in FIG. 4A
is shaped as the first protection structure in the second exemplary
structure. In other words, on a plane (X-Z plane) including the
region A that is the non-bent section (refer to FIG. 2A) and
orthogonal to the installation plane (Y-Z plane), the corner
portion P2 of the lid 320 is defined by: a first lid surface 320a
facing the holding surface 310a of the V-groove substrate 310
provided with the V-groove 311; and a second lid surface 320b
continued to the first lid surface 320a and facing a space side
where the region B corresponding to the bent portion BA is
positioned. In the present embodiment, the corner portion P2 of the
lid is applied with rounding processing so as to have a curved
surface 321 having a curvature radius R.sub.a smaller than a
curvature radius R.sub.b of the bent portion BA of the bent optical
fiber 100 (section corresponding to the region B out of the exposed
section of the glass fiber 110). In other words, a curvature
(=1/R.sub.a [mm]) of the curved surface 321 positioned at the
corner portion P2 of the lid 320 is set larger than a curvature
(=1/R.sub.b [mm]) of the bent portion BA. With this structure, when
a distal end portion (particularly, the region A) of the bent
optical fiber 100 is pressed against the V-groove 311 by the lid
320, a risk such as rupture of the bent optical fiber 100 can be
effectively reduced even in a case where unexpected tensile stress
is applied to the bent optical fiber 100, for example, when the
position of the lid 320 is changed by hardening shrinkage of a
fixing adhesion bond at the time of bonding and fixing the fiber
fixing component 300 onto the electronic substrate 200.
[0053] Meanwhile, a length L1 of the region A housed in the holding
portion constituted by the V-groove 311 of the V-groove substrate
310 and the lid 320 is, preferably, 0.3 mm or more and 1.5 mm or
less. Furthermore, an interval L2 extending along the installation
plane to the bent portion BA from a start position of exposure of
the exposed section of the glass fiber 110, that is, the position
where the glass fiber is exposed from the holding portion of the
fiber fixing component 300 (contact end of the V-groove substrate
310 and the lid 320) is, preferably, 50 [.mu.m] or more and 1 [mm]
or less. More preferably, L2 is 500 [.mu.m] or less. An interval
along the installation plane to the region C from a side surface
farthest from the region C of the bent optical fiber 100 out of
side surfaces of the lid 320, namely, a total height L3 of the
optical connection component is, preferably, 4 [mm] or less. The
curvature d of the bent portion BA is, preferably, 0.4 [l/mm] or
more. The reason is to prevent the total height of the optical
connection component from being unnecessarily high. Additionally, a
curvature radius of the shaped curved surface 321 of the lid 320
positioned at the corner portion P2 is, preferably, 10 [.mu.m] or
more (curvature d=100 [l/mm] or less) in order to obtain an effect
of avoiding stress concentration on the bent optical fiber 100.
[0054] Furthermore, a light entrance/exit end surface of the bent
optical fiber 100 to which the fiber fixing component 300 is fixed
may have a certain angle with respect to a fiber axis (optical axis
AX illustrated in FIG. 5A). For example, a large reflection loss
with a light source, a light receiver, and a waveguide connected to
the bottom surface of the fiber fixing component 300 can be largely
taken by inclining the light input/output end surface by 8
[.degree.] with respect to the fiber axis, and stable transmission
performance can be achieved.
[0055] Next, a third exemplary structure of the optical connection
component according to the present embodiment including the second
protection structure will be described. Meanwhile, FIG. 7A is a
perspective view illustrating an optical connection component
according to the third exemplary structure in which the exposed
section of the bent optical fiber 100 is protected by the potting
resin 400 as an example of the second protection structure, and
FIG. 7B is a view illustrating a bottom surface structure of the
fiber fixing component 300. Additionally, FIGS. 8A and 8B
illustrate views to describe structural features of the potting
resin 400, and particularly, FIG. 8A is a view illustrating a
cross-sectional structure taken along a line X1-X1 (line on the Y-Z
plane) in FIG. 7A, and FIG. 8B is a view illustrating a
cross-sectional structure taken along a line X2-X2 (line on the X-Z
plane) in FIG. 7A.
[0056] The potting resin 400 is tightly fixed to the holding
surface 310a of the V-groove substrate 310 and the second lid
surface 320b of the lid 320 in a state of entirely covering the
exposed section of the bent optical fiber 100 (the surface of the
glass fiber 110 where the resin coating 120 is removed),
particularly, the section exposed from the fiber fixing component
300. Since the entire end portion of the bent optical fiber 100
formed with the bent portion BA is thus covered with the potting
resin 400 firmly fixed to the fiber fixing component 300,
deformation of the bent optical fiber 100 can be suppressed to a
certain level or less even when stress is applied to the bent
optical fiber 100, and as a result, breakage of the bent optical
fiber 100 caused by excessive deformation can be effectively
avoided.
[0057] Meanwhile, the potting resin 400 has strength equivalent to
a Young's modulus of 2.0 MPa or more and functions so as not to
allow main stress of 250 MPa or more to be applied to the bent
portion BA of the bent optical fiber 100. Additionally, needless to
mention, the potting resin 400 also has a function to prevent
damage of the bent optical fiber 100 caused by direct contact. As a
preferable structure, the potting resin 400 may have strength
equivalent to a Young's modulus of 3.5 MPa or more. As a material
of the potting resin 400, for example, a UV curing resin can be
considered, but not limited thereto.
[0058] Furthermore, as illustrated in FIG. 8A, a minimum thickness
of the potting resin 400 is, preferably, 60 .mu.m or more. This is
to avoid direct exposure of the glass fiber 110 in the section
where the resin coating 120 is removed, and maintain protection
strength.
[0059] FIG. 9 is a graph illustrating a relation between a minimum
curvature radius R.sub.min [mm] and displacement [mm] of the bent
optical fiber at the time of pulling the other end portion of the
bent optical fiber 100 (the side to which the connector 250 is
attached) with tension of 10 N in the above-described third
exemplary structure. Meanwhile, as illustrated in FIG. 8B, the
minimum curvature radius R.sub.min represents a minimum curvature
radius out of curvature radii at a curved portion included in a
contour line of the potting resin 400 defined on the plane (X-Z
plane) including the region A positioned at the end portion of the
bent optical fiber 100 and orthogonal to the installation plane
(Y-Z plane). As it can be grasped from the graph of FIG. 9, the
minimum curvature radius R.sub.min is, preferably, 0.6 [mm] or more
in order to suppress displacement of the bent portion BA to 0.5
[mm] or less such that a risk of rupture of the bent optical fiber
100 is reduced. In other words, the contour line defining an outer
shape of the potting resin 400 includes a curved portion having a
curvature d of, preferably, 5/3 [l/mm] or less in order to suppress
displacement of the bent portion BA to 0.5 [mm] or less.
REFERENCE SIGNS LIST
[0060] 100 . . . Bent optical fiber; 110 . . . Glass fiber (bare
fiber); 111 . . . Core; 112 . . . First cladding; 113 . . . Second
cladding; 114 . . . Third cladding; BA . . . Bent portion; 300 . .
. Fiber fixing component; 310 . . . V-groove substrate; 311 . . .
V-groove; 320 . . . Lid; 320a . . . First lid surface; and 320b . .
. Second lid surface.
* * * * *