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| United States Patent |
5,499,309
|
|
Kozuka
, et al.
|
March 12, 1996
|
Method of fabricating optical component including first and second
optical waveguide chips having opposed inclined surfaces
Abstract
A V groove and guide grooves are defined in a ceramic substrate, and an
optical fiber is fixedly disposed in the V groove by the ceramic substrate
and a cover, thereby producing a first optical waveguide chip. A V groove
and guide grooves are also defined in another ceramic substrate, and an
optical fiber is fixedly disposed in the V groove by the ceramic substrate
and a cover, thereby producing a second optical waveguide chip. The first
optical waveguide chip has an end face inclined to the direction of
propagation of light through the optical fiber thereof, and the second
optical waveguide chip also has an end face inclined to the direction of
propagation of light through the optical fiber thereof. The first and
second optical waveguide chips are positioned relatively to each other by
guide pins intimately placed in the guide grooves, and the inclined end
faces extend substantially parallel to each other with an air layer
interposed therebetween. An optical component such as an optical
transmission/reception module thus produced can easily be reduced in size
and cost, and fabricated in an integrated configuration.
| Inventors:
|
Kozuka; Yoshinari (Nagoya, JP);
Osugi; Yukihisa (Nagoya, JP);
Fukuyama; Masashi (Nagoya, JP)
|
| Assignee:
|
NGK Insulators, Ltd. (JP)
|
| Appl. No.:
|
314302 |
| Filed:
|
September 30, 1994 |
Foreign Application Priority Data
| Current U.S. Class: |
385/38; 385/47; 385/48; 385/65 |
| Intern'l Class: |
G02B 006/26 |
| Field of Search: |
385/15-18,31,38,39,44,45,47-52,65,83,147
|
References Cited [Referenced By]
U.S. Patent Documents
| 3970360 | Jul., 1976 | Kersten et al. | 385/39.
|
| 4165496 | Aug., 1979 | Domenico, Jr. et al. | 372/31.
|
| 4285571 | Aug., 1981 | Winzer | 385/47.
|
| 4373775 | Feb., 1983 | Gasparian | 385/47.
|
| 4900118 | Feb., 1990 | Yanagawa et al. | 385/49.
|
| 5390266 | Feb., 1995 | Heitmann et al. | 385/44.
|
| Foreign Patent Documents |
| 0292331 | Nov., 1988 | EP.
| |
| 0509789 | Oct., 1992 | EP.
| |
| 2549243 | Jan., 1985 | FR.
| |
| 63-289509 | Nov., 1988 | JP | 385/47.
|
| 1-118806 | May., 1989 | JP.
| |
Other References
"Optical Fiber Coupling Approaches for Multi-Channel Laser and Detector
Arrays," K. P. Jackson et al., SPIE, vol. 994, Optoelectronic Materials,
Devices, Packaging, and Interconnects II (1988), pp. 40-47 (no month).
|
Primary Examiner: Lee; John D.
Attorney, Agent or Firm: Parkhurst Wendel & Rossi
Claims
What is claimed is:
1. A method of fabricating an optical component, comprising the steps of:
forming a first optical waveguide chip having a first optical waveguide;
forming a second optical waveguide chip having a second optical waveguide
and different from said first optical waveguide chip;
processing said first optical waveguide chip to form a first end face
thereof at which an end of said first optical waveguide is exposed;
polishing said first optical waveguide chip to an optical finish to incline
a second end face thereof at which an opposite end of said first optical
waveguide is exposed, to a direction in which light is propagated through
said first optical waveguide;
processing said second optical waveguide chip to form a third end face
thereof at which an end of said second optical waveguide is exposed;
polishing said second optical waveguide chip to an optical finish to
incline a fourth end face thereof at which an opposite end of said second
optical waveguide is exposed, to a direction in which light is propagated
through said second optical waveguide; and
positioning said first optical waveguide chip and said second optical
waveguide chip relative to each other such that said second and fourth end
faces extend substantially parallel to each other with a layer interposed
therebetween which has a refractive index that is different from the
refractive index of at least one of said first and second optical
waveguides, said first and second optical waveguides being optically
coupled to each other such that a portion of light propagated from said
first optical waveguide to said second optical waveguide is reflected out
of at least one of the first and second optical waveguide chips by at
least one of said second end face of said first optical waveguide chip and
said fourth end face of said second optical waveguide chip, the reflected
light propagating through a light transmissive portion of at least one of
said optical waveguide chips.
2. A method according to claim 1, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in a substrate and fixing the optical fiber in
the V or U groove with the substrate and a cover.
3. A method according to claim 1, wherein both the step of forming a first
optical waveguide chip having a first optical waveguide and the step of
forming a second optical waveguide chip having a second optical waveguide
comprise the steps of placing an optical fiber in a V groove of a V-shaped
cross section or a U groove of a U-shaped cross section which is defined
in a substrate and fixing the optical fiber in the V or U groove with the
substrate and a cover.
4. A method according to claim 1, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the step of diffusing an impurity in a
dielectric substrate to form the optical waveguide in said dielectric
substrate.
5. A method according to claim 1, wherein both the step of forming a first
optical waveguide chip having a first optical waveguide and the step of
forming a second optical waveguide chip having a second optical waveguide
comprise the step of diffusing an impurity in a dielectric substrate to
form the optical waveguide in said dielectric substrate.
6. A method according to claim 5, wherein said step of diffusing an
impurity in a dielectric substrate to form the optical waveguide in said
dielectric substrate comprises the step of diffusing an impurity into a
dielectric substrate made of LiNbO.sub.3, LiTaO.sub.3, glass, or a
semiconductor to form the optical waveguide in said dielectric substrate.
7. A method according to claim 1, wherein said layer comprises one of a
layer of air, a layer of dielectric, or a layer of metal.
8. A method according to claim 1, wherein said layer comprises one of a
layer of dielectric or a layer of metal, and the ends of said first and
second optical waveguides which are exposed at said second and fourth end
faces are held in direct contact with opposite surfaces, respectively, of
said layer and are optically coupled to each other.
9. A method according to claim 1, wherein one of the step of forming a
first optical waveguide chip having a first optical waveguide and the step
of forming a second optical waveguide chip having a second optical
waveguide comprises the steps of placing an optical fiber in a V groove of
a V-shaped cross section or a U groove of a U-shaped cross section which
is defined in a substrate and fixing the optical fiber in the V or U
groove with the substrate and a cover, and wherein the other of the step
of forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the step of diffusing an impurity in a
dielectric substrate to form the optical waveguide in said dielectric
substrate.
10. A method according to claim 1, wherein said step of positioning
comprises the steps of defining first and second guide grooves in said
first and second optical waveguide chips and positioning said first and
second optical waveguide chips with reference to pins intimately held in
said first and second guide grooves.
11. A method according to claim 1, wherein both of the step of forming a
first optical waveguide chip having a first optical waveguide and the step
of forming a second optical waveguide chip having a second optical
waveguide comprise the steps of placing an optical fiber in a V groove of
a V-shaped cross section or a U groove of a U-shaped cross section which
is defined in a substrate and fixing the optical fiber in the V or U
groove with the substrate and a cover, and wherein said step of
positioning comprises the steps of defining first and second guide grooves
in said first and second optical waveguide chips and positioning said
first and second optical waveguide chips with reference to pins intimately
held in said first and second guide grooves.
12. A method according to claim 1, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in a substrate and fixing the optical fiber in
the V or U groove with the substrate and a cover made of a material which
passes light propagated through said optical fiber, said method further
comprising the step of fixing to said cover a light-detecting element for
detecting the light which is reflected out of at least one of the first
and second optical waveguide chips by at least one of said second end face
and said fourth end face.
13. A method according to claim 1, further comprising the step of providing
a light source for introducing light into said second optical waveguide.
14. A method according to claim 13, further comprising the step of
providing an optical coupling means for optically coupling the light from
said light source to the end of said second optical waveguide which is
exposed at said third end face.
15. A method according to claim 1, wherein said step of forming a first
optical waveguide chip having a first optical waveguide comprises the step
of forming a first optical waveguide having a plurality of parallel
optical waveguides, and said step of forming a second optical waveguide
chip having a second optical waveguide comprises the step of forming a
second optical waveguide having a plurality of parallel optical
waveguides.
16. A method according to claims 1, further comprising the step of
providing a light-detecting element for detecting the light which is
reflected out of at least one of the first and second optical waveguide
chips by at least one of said second end face and said fourth end face.
17. A method of fabricating an optical component, comprising the steps of:
forming a first optical waveguide chip having a first optical waveguide;
forming a second optical waveguide chip having a second optical waveguide
which has a refractive index different from the refractive index of said
first optical waveguide, and different from said first optical waveguide
chip;
processing said first optical waveguide chip to form a first end face
thereof at which an end of said first optical waveguide is exposed;
polishing said first optical waveguide chip to an optical finish to incline
a second end face thereof at which an opposite end of said first optical
waveguide is exposed, to a direction in which light is propagated through
said first optical waveguide;
processing said second optical waveguide chip to form a third end face
thereof at which an end of said second optical waveguide is exposed;
polishing said second optical waveguide chip to an optical finish to
incline a fourth end face thereof at which an opposite end of said second
optical waveguide is exposed, to a direction in which light is propagated
through said second optical waveguide; and
positioning said first optical waveguide chip and said second optical
waveguide chip relative to each other such that said second and fourth end
faces extend substantially parallel to each other, the ends of said first
and second optical waveguides which are exposed at said second and fourth
end faces being held in direct contact with each other and being optically
coupled to each other such that a portion of light propagated from said
first optical waveguide to said second optical waveguide is reflected out
of at least one of the first and second optical waveguide chips by at
least one of said second end face of said first optical waveguide chip and
said fourth end face of said second optical waveguide chip, the reflected
light propagating through a light transmissive portion of at least one of
said optical waveguide chips.
18. A method according to claim 17, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in a substrate and fixing the optical fiber in
the V or U groove with the substrate and a cover.
19. A method according to claim 17, wherein both of the step of forming a
first optical waveguide chip having a first optical waveguide and the step
of forming a second optical waveguide chip having a second optical
waveguide comprise the steps of placing an optical fiber in a V groove of
a V-shaped cross section or a U groove of a U-shaped cross section which
is defined in a substrate and fixing the optical fiber in the V or U
groove with the substrate and a cover.
20. A method according to claim 17, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the step of diffusing an impurity in a
dielectric substrate to form the optical waveguide in said dielectric
substrate.
21. A method according to claim 20, wherein said step of diffusing an
impurity in a dielectric substrate to form the optical waveguide in said
dielectric substrate comprises the step of diffusing an impurity into a
dielectric substrate made of LiNbO.sub.3, LiTaO.sub.3, glass, or a
semiconductor to form the optical waveguide in said dielectric substrate.
22. A method according to claim 17, wherein both of the step of forming a
first optical waveguide chip having a first optical waveguide and the step
of forming a second optical waveguide chip having a second optical
waveguide comprise the step of diffusing an impurity in a dielectric
substrate to form the optical waveguide in said dielectric substrate.
23. A method according to claim 17, wherein one of the step of forming a
first optical waveguide chip having a first optical waveguide and the step
of forming a second optical waveguide chip having a second optical
waveguide comprises the steps of placing an optical fiber in a V groove of
a V-shaped cross section or a U groove of a U-shaped cross section which
is defined in a substrate and fixing the optical fiber in the V or U
groove with the substrate and a cover, and wherein-the other of the step
of forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the step of diffusing an impurity in a
dielectric substrate to form the optical waveguide in said dielectric
substrate.
24. A method according to claim 17, wherein said step of positioning
comprises the steps of defining first and second guide grooves in said
first and second optical waveguide chips and positioning said first and
second optical waveguide chips with reference to pins intimately held in
said first and second guide grooves.
25. A method according to claim 17, wherein at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide comprises the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in a substrate and fixing the optical fiber in
the V or U groove with the substrate and a cover made of a material which
passes light propagated through said optical fiber, said method further
comprising the step of fixing to said cover a light-detecting element for
detecting the light which is reflected out of at least one of the first
and second optical waveguide chips by at least one of said second end face
and said fourth end face.
26. A method according to claim 17, further comprising the step of
providing a light source for introducing light into said second optical
waveguide.
27. A method according to claim 26, further comprising the step of
providing an optical coupling means for optically coupling the light from
said light source to the end of said second optical waveguide which is
exposed at said third end face.
28. A method according to claim 17, wherein said step of forming a first
optical waveguide chip having a first optical waveguide comprises the step
of forming a first optical waveguide having a plurality of parallel
optical waveguides, and said step of forming a second optical waveguide
chip having a second optical waveguide comprises the step of forming a
second optical waveguide having a plurality of parallel optical
waveguides.
29. A method according to claim 17, further comprising the step of
providing a light-detecting element for detecting the light which is
reflected out of at least one of the first and second optical waveguide
chips by at least one of said second end face and said fourth end face.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of fabricating an optical
component, and more particularly to a method of fabricating an optical
transmission/reception module for use in optical CATV and optical
communication fields.
2. Description of the Related Art
As the optical fiber transmission technology advances, various research
activities are directed to optical CATV and optical communication systems
which utilize the wide-band characteristics of the optical fibers. It is
expected that there will be realized a Fiber-To-The-Home (FTTH) system
which has optical fibers led to homes for starting various information
services in the near future. For realizing a full-fledged FTTH system, it
is necessary to reduce the size and cost of optical terminals connected to
respective homes.
The FTTH system requires a bidirectional optical transmission mode which
needs to be performed by an optical reception/transmission module
comprising a light source for emitting an optical signal, a
light-detecting element for converting the optical signal into an electric
signal, and an optical coupler for transmitting light from the optical
source and light to the light-detecting element to optical fibers that are
used to transmit light.
FIG. 1 of the accompanying drawings schematically shows a conventional
optical reception/transmission module A. As shown in FIG. 1, the optical
reception/transmission module A comprises a laser diode 1, a photodiode 2,
and an optical coupler 3. The optical coupler 3 comprises two optical
fibers 4, 5 fused together. Therefore, it is difficult to reduce the
length of the optical coupler 3. The optical coupler 3 and the laser diode
1, and the optical coupler 3 and the photodiode 2 are connected to each
other by optical fibers through fused regions 6 thereof. Consequently, the
optical reception/transmission module A is relatively long in its
entirety. If a plurality of optical reception/transmission modules A are
required, then since the individual optical reception/transmission modules
A have to be arrayed horizontally or vertically, the space taken up by the
optical reception/transmission modules A increases and the cost of the
entire system also increases as the number of optical
reception/transmission modules A increases.
As described above, inasmuch as the optical coupler 3 is composed of the
two optical fibers 4, 5 fused together and the optical
reception/transmission module A is made up of three components, i.e., the
laser diode 1, the photodiode 2, and the optical coupler 3, the
conventional optical reception/transmission module A has been problematic
with respect to both the space occupied thereby and the cost thereof. In
the case where the optical reception/transmission module A is incorporated
in an on-demand access system of CATV, it is necessary to use many optical
couplers 3 and optical reception/transmission modules A in a transmission
terminal. Therefore, such an on-demand access system with the conventional
optical couplers 3 and optical reception/transmission modules A takes up a
large space and is expensive.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of fabricating
an optical component such as an optical coupler or an optical
reception/transmission module in a manner to reduce the size thereof.
Another object of the present invention is to provide a method of
fabricating an optical component such as an optical coupler or an optical
reception/transmission module easily in an integrated configuration, so
that the optical component can be reduced in size and cost.
According to the present invention, there is provided a method of
fabricating an optical component, comprising the steps of:
forming a first optical waveguide chip having a first optical waveguide;
forming a second optical waveguide chip having a second optical waveguide
and different from said first optical waveguide chip;
processing said first optical waveguide chip to form a first end face
thereof at which an end of said first optical waveguide is exposed;
polishing said first optical waveguide chip to an optical finish to incline
a second end face thereof at which an opposite end of said first optical
waveguide is exposed, to a direction in which light is propagated through
said first optical waveguide;
processing said second optical waveguide chip to form a third end face
thereof at which an end of said second optical waveguide is exposed;
polishing said second optical waveguide chip to an optical finish to
incline a fourth end face thereof at which an opposite end of said second
optical waveguide is exposed, to a direction in which light is propagated
through said second optical waveguide; and
positioning said first optical waveguide chip and said second optical
waveguide chip relatively to each other such that said second and fourth
end faces extend substantially parallel to each other with a layer
interposed therebetween which has a refractive index that is different
from the refractive index of at least one of said first and second optical
waveguides, said first and second optical waveguides are optically coupled
to each other, and a portion of light propagated from said first optical
waveguide to said second optical waveguide is reflected out of at least
one of the first and second optical waveguide chips by at least one of
said second end face of said first optical waveguide chip and said fourth
end face of said second optical waveguide chip.
According to the above method, the first optical waveguide chip having the
first optical waveguide is formed and polished to an optical finish such
that the second end face of the first optical waveguide chip where the end
of the first optical waveguide is exposed is inclined to the direction of
propagation of light through the first optical waveguide, and the second
optical waveguide chip having the second optical waveguide and different
from the first optical waveguide chip is formed and polished to an optical
finish such that the fourth end face of the second optical waveguide chip
where the end of the second optical waveguide is exposed is inclined to
the direction of propagation of light through the second optical
waveguide. The first and second optical waveguides are positioned
relatively to each other such that the second and fourth end faces extend
substantially parallel to each other with a layer interposed therebetween
which has a refractive index that is different from the refractive index
of at least one of the first and second optical waveguides. A portion of
light propagated from the first optical waveguide to the second optical
waveguide is reflected out of at least one of the first and second optical
waveguide chips by at least one of the second and fourth end faces of the
first and second optical waveguide chips.
According to the present invention, there is also provided a method of
fabricating an optical component, comprising the steps of:
forming a first optical waveguide chip having a first optical waveguide;
forming a second optical waveguide chip having a second optical waveguide
which has a refractive index different from the refractive index of said
first optical waveguide, and different from said first optical waveguide
chip;
processing said first optical waveguide chip to form a first end face
thereof at which an end of said first optical waveguide is exposed;
polishing said first optical waveguide chip to an optical finish to incline
a second end face thereof at which an opposite end of said first optical
waveguide is exposed, to a direction in which light is propagated through
said first optical waveguide;
processing said second optical waveguide chip to form a third end face
thereof at which an end of said second optical waveguide is exposed;
polishing said second optical waveguide chip to an optical finish to
incline a fourth end face thereof at which an opposite end of said second
optical waveguide is exposed, to a direction in which light is propagated
through said second optical waveguide; and
positioning said first optical waveguide chip and said second optical
waveguide chip relatively to each other such that said second and fourth
end faces extend substantially parallel to each other, the ends of said
first and second optical waveguides which are exposed at said second and
fourth end faces are held in direct contact with each other and optically
coupled to each other, and a portion of light propagated from said first
optical waveguide to said second optical waveguide is reflected out of at
least one of the first and second optical waveguide chips by at least one
of said second end face of said first optical waveguide chip and said
fourth end face of said second optical waveguide chip.
According to the above method, the first optical waveguide chip having the
first optical waveguide is formed and polished to an optical finish such
that the second end face of the first optical waveguide where the end of
the first optical waveguide chip is exposed is inclined to the direction
of propagation of light through the first optical waveguide, and the
second optical waveguide chip having the second optical waveguide whose
refractive index differs from that of the first optical waveguide and
different from the first optical waveguide chip is formed and polished to
an optical finish such that the fourth end face of the second optical
waveguide chip where the end of the second optical waveguide is exposed is
inclined to the direction of propagation of light through the second
optical waveguide. The first and second optical waveguides are positioned
relatively to each other such that the second and fourth end faces extend
substantially parallel to each other and the exposed ends of the first and
second optical waveguides are held in direct contact with each other and
optically coupled to each other. A portion of light propagated from the
first optical waveguide to the second optical waveguide is reflected out
of at least one of the first and second optical waveguide chips by at
least one of the second and fourth end faces of the first and second
optical waveguide chips.
Therefore, since a portion of light propagated from the first optical
waveguide to the second optical waveguide is reflected out of at least one
of the first and second optical waveguide chips by at least one of the
second and fourth end faces of the first and second optical waveguide
chips, the optical component has a length smaller than a conventional
optical component which is composed of two optical fibers fused to each
other.
The first optical waveguide is disposed in the first optical waveguide
chip, and the second optical waveguide chip is disposed in the second
optical waveguide chip, and the first and second optical waveguides are
optically coupled to each other and light is emitted from the first
optical waveguide chip and/or the second optical waveguide chip by the
inclined end faces of the first and second optical waveguide chips. If a
plurality of light paths are required, then a plurality of first optical
waveguides may be disposed in the first optical waveguide chip, and a
plurality of second optical waveguides may be disposed in the second
optical waveguide chip. As a result, the optical component may easily be
fabricated in an integrated configuration, and reduced in size and cost.
In the case where the second optical waveguide whose refractive index
differs from that of the first optical waveguide is disposed in the second
optical waveguide chip, even though the first and second optical
waveguides are positioned relatively to each other such that the exposed
ends of the first and second optical waveguides are held in direct contact
with each other and optically coupled to each other, a portion of light
propagated from the first optical waveguide to the second optical
waveguide is reflected out of at least one of the first and second optical
waveguide chips. Consequently, the first and second optical waveguide
chips can easily be positioned relatively to each other.
At least one or both of the step of forming the first optical waveguide
chip having the first optical waveguide and the step of forming the second
optical waveguide chip having the second optical waveguide may comprise
the steps of placing an optical fiber in a V groove of a V-shaped cross
section or a U groove of a U-shaped cross section which is defined in the
substrate and fixing the optical fiber in the V or U groove with the
substrate and the cover. With such a process, the first optical waveguide
and/or the second optical waveguide becomes an optical fiber. Since this
optical fiber is of the same material as the optical fiber used for
transmission, these optical fibers can easily be spliced to each other
with a small optical loss.
If the first optical waveguide and/or the second optical waveguide is
formed by a process including the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in the substrate and fixing the optical fiber in
the V or U groove with the substrate and the cover, then the optical fiber
is positioned accurately in the optical waveguide chip. Even though the
first optical waveguide and/or the second optical waveguide is an optical
fiber, since the cover is disposed over the optical fiber, a
light-detecting element for detecting light emitted out of the first
optical waveguide and/or the second optical waveguide may be disposed on
the cover. Therefore, the light-detecting element may be installed with
ease.
At least one or both of the step of forming the first optical waveguide
chip having the first optical waveguide and the step of forming the second
optical waveguide chip having the second optical waveguide may comprise
the step of diffusing an impurity in a dielectric substrate to form an
optical waveguide in the dielectric substrate. With such a process, a
number of optical waveguides may easily be formed in a substrate, and may
easily be fabricated in an integrated configuration. Where the first
optical waveguide and/or the second optical waveguide is in the form of an
optical waveguide formed by diffusing an impurity in the dielectric
substrate, a light-detecting element or the like may easily be placed on
the dielectric substrate even without placing a cover on the dielectric
substrate.
Preferably, said step of diffusing an impurity in a dielectric substrate to
form the optical waveguide in said dielectric substrate comprises the step
of diffusing an impurity into a dielectric substrate made of LiNbO.sub.3,
LiTaO.sub.3, glass, or a semiconductor to form the optical waveguide in
said dielectric substrate.
In the case where the second and fourth end faces extend substantially
parallel to each other with a layer interposed therebetween which has a
refractive index that is different from the refractive index of at least
one of said first and second optical waveguides, the second and fourth end
faces preferably extend substantially parallel to each other with a layer
of air, a dielectric, or metal interposed therebetween.
If the layer interposed between the second and fourth end faces is an air
layer, the layer should preferably have a thickness in the range of from
0.5 to 10 .mu.m. If the thickness of the layer were smaller than 0.5
.mu.m, then a portion of light propagated from said first optical
waveguide to said second optical waveguide would not be practically
sufficiently reflected by at least one of said second end face of said
first optical waveguide chip and said fourth end face of said second
optical waveguide chip. If the thickness of the layer were greater than 10
.mu.m, then the intensity of light propagated from said first optical
waveguide to said second optical waveguide would be too low.
In the case where the second and fourth end faces extend substantially
parallel to each other with a layer interposed therebetween which has a
refractive index that is different from the refractive index of at least
one of said first and second optical waveguides, the second and fourth end
faces preferably extend substantially parallel to each other with a layer
of a dielectric or metal interposed therebetween. With the layer of a
dielectric or metal being interposed between the second and fourth end
faces, the ends of the first and second optical waveguides which are
exposed at said second and fourth end faces are held in direct contact
with opposite surfaces, respectively, of said layer.
Consequently, the distance between the exposed ends of the first and second
optical waveguides is determined highly accurately, and hence it is
possible to determine with accuracy an intensity of light which is
transmitted from the first optical waveguide to the second optical
waveguide and an intensity of light which is emitted out of at least one
of the first and second optical waveguide chips.
Since the dielectric or metal layer is interposed between the exposed ends
of the first and second optical waveguides, the intensity of light which
is transmitted from the first optical waveguide to the second optical
waveguide and the intensity of light which is emitted out of at least one
of the first and second optical waveguide chips can easily be controlled
by selecting a material of the dielectric or metal layer.
One of the step of forming a first optical waveguide chip having a first
optical waveguide and the step of forming a second optical waveguide chip
having a second optical waveguide may comprise the steps of placing an
optical fiber in a V groove of a V-shaped cross section or a U groove of a
U-shaped cross section which is defined in a substrate and fixing the
optical fiber in the V or U groove with the substrate and a cover, and the
other may comprise the step of diffusing an impurity in a dielectric
substrate to form the optical waveguide in said dielectric substrate.
The step of positioning said first optical waveguide chip and said second
optical waveguide chip relatively to each other may comprise the steps of
defining first and second guide grooves in said first and second optical
waveguide chips and positioning said first and second optical waveguide
chips with reference to pins intimately held in said first and second
guide grooves. Using the first and second guide grooves and the guide
pins, it is possible to position the first and second optical waveguides
easily with respect to each other.
Both of the step of forming a first optical wave- guide chip having a first
optical waveguide and the step of forming a second optical waveguide chip
having a second optical waveguide may comprise the steps of placing an
optical fiber in a V groove of a V-shaped cross section or a U groove of a
U-shaped cross section which is defined in a substrate and fixing the
optical fiber in the V or U groove with the substrate and a cover, and the
step of positioning said first optical waveguide chip and said second
optical waveguide chip relatively to each other may comprise the steps of
defining first and second guide grooves in said first and second optical
waveguide chips and positioning said first and second optical waveguide
chips with reference to pins intimately held in said first and second
guide grooves.
The method according to the present invention may further comprise the step
of providing a light-detecting element for detecting the light which is
reflected out of at least one of the first and second optical waveguide
chips by at least one of said second end face and said fourth end face.
If the light-detecting element is employed, at least one of the step of
forming a first optical waveguide chip having a first optical waveguide
and the step of forming a second optical waveguide chip having a second
optical waveguide should preferably comprise the steps of placing an
optical fiber in a V groove of a V-shaped cross section or a U groove of a
U-shaped cross section which is defined in a substrate and fixing the
optical fiber in the V or U groove with the substrate and a cover made of
a material which passes light propagated through said optical fiber, and
the light-detecting element is fixed to the cover.
The method according to the present invention may further comprise the step
of providing a light source for introducing light into said second optical
waveguide.
The method according to the present invention may further comprise the step
of providing an optical coupling means for optically coupling the light
from said light source to the end of said second optical waveguide which
is exposed at said third end face.
The step of forming a first optical waveguide chip having a first optical
waveguide may comprise the step of forming a first optical waveguide
having a plurality of parallel optical waveguides, and said step of
forming a second optical waveguide chip having a second optical waveguide
may comprise the step of forming a second optical waveguide having a
plurality of parallel optical waveguides. With these steps, a highly
integrated optical component may be produced.
The angle formed between the second end face of the first optical waveguide
and the direction of propagation of light through the first optical
waveguide, and the angle formed between the fourth end face of the second
optical waveguide and the direction of propagation of light through the
second optical waveguide should preferably be 80.degree. or less. If these
angles were greater than 80.degree., then the angle of reflection would be
too small, and the distance between the reflecting surfaces and the
light-detecting element would be too large, resulting in a widely spread
light beam and a reduced intensity of detected light.
The angle formed between the second end face of the first optical waveguide
and the direction of propagation of light through the first optical
waveguide, and the angle formed between the fourth end face of the second
optical waveguide and the direction of propagation of light through the
second optical waveguide should more preferably be the Brewster's angle or
less. The angle of incidence ranging between the Brewster's angle and the
critical angle allows the reflectivity to be large.
However, the angle formed between the second end face of the first optical
waveguide and the direction of propagation of light through the first
optical waveguide, and the angle formed between the fourth end face of the
second optical waveguide and the direction of propagation of light through
the second optical waveguide should be (90.degree.-- critical angle) or
more.
The above and other objects, features, and advantages of the present
invention will become apparent from the following description when taken
in conjunction with the accompanying drawings which illustrate preferred
embodiments of the present invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a conventional optical reception/transmission
module;
FIG. 2 is a perspective view illustrating a method of fabricating an
optical component according to a first embodiment of the present
invention;
FIG. 3 is a cross-sectional view illustrating the method of fabricating an
optical component according to the first embodiment of the present
invention;
FIG. 4 is a side elevational view illustrating the method of fabricating an
optical component according to the first embodiment of the present
invention;
FIG. 5 is a perspective view illustrating a method of fabricating an
optical component according to a second embodiment of the present
invention;
FIG. 6 is a cross-sectional view illustrating the method of fabricating an
optical component according to the second embodiment of the present
invention;
FIG. 7 is a perspective view illustrating a method of fabricating an
optical component according to a third embodiment of the present
invention;
FIG. 8 is a cross-sectional view illustrating the methods of fabricating an
optical component according to the first and second embodiments of the
present invention;
FIG. 9 is a cross-sectional view illustrating a method of fabricating an
optical component according to a fourth embodiment of the present
invention;
FIG. 10 is a cross-sectional view illustrating a method of fabricating an
optical component according to a fifth embodiment of the present
invention;
FIG. 11 is a cross-sectional view illustrating a method of fabricating an
optical component according to a sixth embodiment of the present
invention;
FIG. 12 is a cross-sectional view illustrating a method of fabricating an
optical component according to a seventh embodiment of the present
invention;
FIG. 13 is a cross-sectional view illustrating a method of fabricating an
optical component according to an eighth embodiment of the present
invention;
FIG. 14 is a cross-sectional view illustrating a method of fabricating an
optical component according to a ninth embodiment of the present
invention; and
FIG. 15 is a cross-sectional view illustrating a method of fabricating an
optical component according to a tenth embodiment of the present invention
.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 4, an optical reception/transmission module 200 fabricated
according to the present invention has a package 250 with a single-mode
optical fiber 16 extending from one end thereof. An optical connector 18
such as an FC connector is connected to a distal end of the optical fiber
16 remote from the package 250.
As shown in FIG. 3, the package 250 houses a component assembly 210
therein. The component assembly 210 comprises a first optical waveguide
chip 10, a second optical waveguide chip 30, a photodiode module 80
mounted on the first optical waveguide chip 10, and a laser diode module
70 mounted on an end face 46 of the second optical waveguide chip 30.
The photodiode module 80 has a photodiode 82 disposed therein. The laser
diode module 70 includes a laser diode 72 and a lens 74 for converging a
laser beam 71 emitted from the laser diode 72 onto an optical fiber 36.
As shown in FIGS. 2 and 3, the first optical waveguide chip 10 comprises a
ceramic substrate 12 and a cover 22 of quartz. The ceramic substrate 12
has a V groove 14 having a V-shaped cross section for placing the optical
fiber 16 therein and a pair of guide grooves 20, the V groove 14 and the
guide grooves 20 being defined in an upper surface of the ceramic
substrate 12. The optical fiber 16 has an end portion fixedly disposed in
the V groove 14 by the ceramic substrate 12 and the cover 22. The optical
connector 18 is joined to the opposite distal end of the optical fiber 16.
The photodiode module 80 is fixedly mounted on an upper surface of the
cover 22.
The second optical waveguide chip 30 comprises a ceramic substrate 32 and a
cover 42. The ceramic substrate 32 has a V groove 34 having a V-shaped
cross section for placing a single-mode optical fiber 36 therein and a
pair of guide grooves 40, the V groove 34 and the guide grooves 40 being
defined in an upper surface of the ceramic substrate 32. The optical fiber
36 is fixedly disposed in the V groove 34 by the ceramic substrate 32 and
the cover 42. The end face 46 of the second optical waveguide chip 30 is
polished to an optical finish such that it lies at 90.degree. with respect
to the direction in which light 96 is propagated through the optical fiber
36. The laser diode module 70 is attached to the end face 46. The V
grooves 14, 34 may be replaced with U grooves each having a U-shaped cross
section.
The first optical waveguide chip 10 has an end face 24 polished to an
optical finish such that it is inclined at .theta.=62.degree. with respect
to the direction in which light 90 is propagated through the optical fiber
16. The second optical waveguide chip 30 has an end face 44 polished to an
optical finish such that it is inclined at .theta.=62.degree. with respect
to the direction in which light 96 is propagated through the optical fiber
36. Guide pins 50 are intimately inserted in the guide grooves 20, 40,
thereby positioning the first optical waveguide chip 10 and the second
optical waveguide chip 30 relatively to each other.
The end faces 24, 44 of the first and second optical waveguide chips 10, 30
extend substantially parallel to each other with an air layer 60
interposed therebetween, the air layer 60 having a thickness of about 5
.mu.m. With such an arrangement, the optical fibers 16, 36 are optically
coupled to each other, and a portion of light propagated from the optical
fiber 16 to the optical fiber 36 is reflected into the photodiode 82 by
the end faces 24, 44.
A method of fabricating the optical reception/transmission module according
to a first embodiment of the present invention will be described below.
As shown in FIGS. 2 and 3, a ceramic substrate 12 having a length of 5 mm,
a width of 5 mm, and a thickness of 3 mm is prepared, and a V groove 14
having a V-shaped cross section is defined centrally in the ceramic
substrate 12 for accommodating a single-mode optical fiber 16 which has a
diameter of 125 .mu.m, and two guide grooves 20 are defined in the ceramic
substrate 12 one on each side of the V groove 14 for accommodating
respective rod-shaped guide pins 50 each having a diameter of 700 .mu.m.
Then, an end portion of the optical fiber 16, which is 125 .mu.m across and
2 m long, is placed in the V groove 14, with the optical connector 18
connected to the other end of the optical fiber 16.
Thereafter, a cover 22 of quartz having a thickness of 0.3 mm is placed on
the ceramic substrate 12 over the optical fiber 16, and the ceramic
substrate 12, the optical fiber 16, and the cover 22 are joined to each
other by a resin adhesive.
The ceramic substrate 12, the optical fiber 16, and the cover 22 which are
thus bonded jointly have an end face 24 cut and polished to an optical
finish such that the end face 24 is inclined at .theta.=62.degree. with
respect to the direction in which light 90 is propagated through the
optical fiber 16. In this manner, the first optical waveguide chip 10 is
produced.
A ceramic substrate 32 having a length of 5 mm, a width of 5 mm, and a
thickness of 3 mm is prepared, and a V groove 34 having a V-shaped cross
section is defined centrally in the ceramic substrate 32 for accommodating
a single-mode optical fiber 36 which has a diameter of 125 .mu.m, and two
guide grooves 40 are defined in the ceramic substrate 32 one on each side
of the V groove 34 for accommodating the respective rod-shaped guide pins
50.
Then, the optical fiber 36, which is 125 .mu.m across and 5 mm long, is
placed in the V groove 34.
Thereafter, a cover 42 having a thickness of 0.3 mm is placed on the
ceramic substrate 32 over the optical fiber 36, and the ceramic substrate
32, the optical fiber 36, and the cover 42 are joined to each other by a
resin adhesive.
The ceramic substrate 32, the optical fiber 36, and the cover 42 which are
thus bonded jointly have an end face 44 cut and polished to an optical
finish such that the end face 44 is inclined at .theta.=62.degree. with
respect to the direction in which light 96 is propagated through the
optical fiber 36. In this manner, the second optical waveguide chip 30 is
produced.
Thereafter, a photodiode 82 is disposed above the first optical waveguide
chip 10. Specifically, a photodiode module 80 is directly placed on and
fixed to the upper surface of the cover 22, and the photodiode 82 in the
photodiode module 80 is spaced 0.2 mm from the cover 22.
A laser diode module 70 which has a laser diode 72 and a lens 74 is
attached to the end face 46 of the second optical waveguide chip 30 such
that a laser beam 71 emitted from the laser diode 72 will be converged
onto the optical fiber 36.
Guide pins 50 are inserted into the guide grooves 20 of the first optical
waveguide chip 10 and the guide grooves 40 of the second optical waveguide
chip 30 for aligning the optical axes of the optical fibers 16, 36 with
each other. The end face 24 of the first optical waveguide chip 10 and the
end face 44 of the second optical waveguide chip 30 are positioned
parallel to each other such that the air layer 60 between the end faces
24, 44 has a thickness of about 5 .mu.m. Then, a molten resin material is
introduced into the guide grooves 20, 40, thereby integrally joining the
first optical waveguide chip 10, the second optical waveguide chip 30, and
the guide pins 50. In this manner, the component assembly 210 is produced.
Then, as shown in FIG. 4, the component assembly 210 is housed in a package
250, thereby completing the optical reception/transmission module 200.
Leads 76 attached to the package 250 are electrically connected to the
laser diode 72, and leads 86 attached to the package 250 are electrically
connected to the photodiode 82. The leads 86 are connected to leads 84
(see FIG. 3).
The optical reception/transmission module 200 was measured for its
characteristics. The light which was transmitted from the optical fiber 16
to the optical fiber 36 was about 60% of the light propagated through the
optical fiber 16, and the light reflected as light 92, 94 by the end faces
24, 44 and having reached the photodiode 82 was about 5% of the light
propagated through the optical fiber 16.
FIGS. 5 and 6 illustrate a method of fabricating an optical component
according to a second embodiment of the present invention.
An optical reception/transmission module 200 fabricated according to the
second embodiment of the present invention differs from the optical
reception/transmission module 200 fabricated according to the first
embodiment in that a titanium (Ti) film 62 is disposed on the end face 44
of the second optical waveguide chip 30 and held in contact with the end
face 24 of the first optical waveguide chip 10. The other structural
details of the optical reception/transmission module 200 shown in FIGS. 5
and 6 are the same as those of the optical reception/transmission module
200 shown in FIGS. 2 and 3.
The method of fabricating an optical component according to the second
embodiment of the present invention will be described below.
As shown in FIGS. 5 and 6, a ceramic substrate 12 having a length of 5 mm,
a width of 5 mm, and a thickness of 3 mm is prepared, and a V groove 14
having a V-shaped cross section is defined centrally in the ceramic
substrate 12 for accommodating a single-mode optical fiber 16 which has a
diameter of 125 .mu.m, and two guide grooves 20 are defined in the ceramic
substrate 12 one on each side of the V groove 14 for accommodating
respective rod-shaped guide pins 50 each having a diameter of 700 .mu.m.
Then, an end portion of the optical fiber 16, which is 125 .mu.m across and
2 m long, is placed in the V groove 14, with the optical connector 18
connected to the other end of the optical fiber 16.
Thereafter, a cover 22 having a thickness of 0.3 mm is placed on the
ceramic substrate 12 over the optical fiber 16, and the ceramic substrate
12, the optical fiber 16, and the cover 22 are joined to each other by a
resin adhesive.
The ceramic substrate 12, the optical fiber 16, and the cover 22 which are
thus bonded jointly have an end face 24 cut and polished to an optical
finish such that the end face 24 is inclined at .theta.=62.degree. with
respect to the direction in which light 90 is propagated through the
optical fiber 16. In this manner, the first optical waveguide chip 10 is
produced.
A ceramic substrate 32 having a length of 5 mm, a width of 5 mm, and a
thickness of 3 mm is prepared, and a V groove 34 having a V-shaped cross
section is defined centrally in the ceramic substrate 32 for accommodating
a single-mode optical fiber 36 which has a diameter of 125 .mu.m, and two
guide grooves 40 are defined in the ceramic substrate 32 one on each side
of the V groove 34 for accommodating the respective rod-shaped guide pins
50.
Then, the optical fiber 36, which is 125 .mu.m across and 5 mm long, is
placed in the V groove 34.
Thereafter, a cover 42 having a thickness of 0.3 mm is placed on the
ceramic substrate 32 over the optical fiber 36, and the ceramic substrate
32, the optical fiber 36, and the cover 42 are joined to each other by a
resin adhesive.
The ceramic substrate 32, the optical fiber 36, and the cover 42 which are
thus bonded jointly have an end face 44 cut and polished to an optical
finish such that the end face 44 is inclined at .theta.=62.degree. with
respect to the direction in which light 96 is propagated through the
optical fiber 36. Thereafter, a Ti film 62 having a thickness of 300 .ANG.
is disposed on the inclined end face 44. An opposite end face 46 is
polished to an optical finish such that it lies at 90.degree. with respect
to the direction in which the light 96 is propagated through the optical
fiber 36. In this manner, the second optical waveguide chip 30 is
produced.
Thereafter, a photodiode 82 is disposed above the first optical waveguide
chip 10. Specifically, a photodiode module 80 is directly placed on and
fixed to the upper surface of the cover 22, and the photodiode 82 in the
photodiode module 80 is spaced 0.2 mm from the cover 22.
A laser diode module 70 which has a laser diode 72 and a lens 74 is
attached to the end face 46 of the second optical waveguide chip 30 such
that a laser beam 71 emitted from the laser diode 72 will be converged
onto the optical fiber 36.
Guide pins 50 are inserted into the guide grooves 20 of the first optical
waveguide chip 10 and the guide grooves 40 of the second optical waveguide
chip 30 for aligning the optical axes of the optical fibers 16, 36 with
each other. The end face 24 of the first optical waveguide chip 10 and the
Ti film 62 on the end face 44 of the second optical waveguide chip 30 are
held in abutment against each other. Then, a molten resin material is
introduced into the guide grooves 20, 40, thereby integrally joining the
first optical waveguide chip 10, the second optical waveguide chip 30, and
the guide pins 50. In this manner, the component assembly 210 is produced.
Then, as shown in FIG. 4, the component assembly 210 is housed in a package
250, thereby completing the optical reception/transmission module 200.
Leads 76 attached to the package 250 are electrically connected to the
laser diode 72, and leads 86 attached to the package 250 are electrically
connected to the photodiode 82. The leads 86 are connected to leads 84
(see FIG. 3).
The optical reception/transmission module 200 shown in FIGS. 5 and 6 was
measured for its characteristics. The light which was transmitted from the
optical fiber 16 to the optical fiber 36 was about 50% of the light
propagated through the optical fiber 16, and the light reflected as light
92, 94 by the end faces 24, 44 and having reached the photodiode 82 was
about 10% of the light propagated through the optical fiber 16.
In the optical reception/transmission module 200 shown in FIGS. 5 and 6,
the end faces 24, 44 are positioned in sandwiching relation to the Ti film
62 and held in contract with the Ti film 62. Therefore, any irregularities
of the distance between the end faces 24, 44 are minimized, and hence
characteristic variations of the optical reception/transmission module 200
are also minimized.
FIG. 7 illustrates a method of fabricating an optical component according
to a third embodiment of the present invention.
As shown in FIG. 7, an optical reception/transmission module 300 comprises
a first optical waveguide chip 110, a second optical waveguide chip 130, a
photodiode array 180 mounted on the first optical waveguide chip 110, a
laser diode array 172 spaced from the second optical waveguide chip 30,
and a lens array 174 disposed between the laser diode array 172 and the
second optical waveguide chip 130.
The laser diode array 172 comprises four laser diodes 171, and the lens
array 174 comprises four lenses 173. Laser beams 175 emitted from the four
laser diodes 171 are converged onto four single-mode optical fibers 136,
respectively, by the four lenses 173. The photodiode array 180 comprises
four photodiodes (not shown), and eight leads 184 extend from the
photodiode array 180.
The first optical waveguide chip 110 has a substrate 112 of LiNbO.sub.3.
Four Ti-diffused optical waveguides 117 are formed at a pitch or spacing
of 5 mm on an upper surface of the substrate 112 of LiNbO.sub.3. The
substrate 112 of LiNbO.sub.3 has an end face 126 polished to an optical
finish such that it lies at 90.degree. with respect to the direction in
which light is propagated through the Ti-diffused optical waveguides 117.
An optical fiber array 116 is composed of four optical fibers 115 whose
respective ends are aligned with and secured to the Ti-diffused optical
waveguides 117, respectively. Optical connectors (not shown) are connected
respectively to the other end of the optical fiber array 116. The
photodiode array 180 is fixedly mounted on an upper surface of the
substrate 112 of LiNbO.sub.3.
The substrate 112 may be made of LiTaO.sub.3, glass, or a semiconductor.
The second optical waveguide chip 130 has a ceramic substrate 132, a cover
142, and four optical fibers 136. The ceramic substrate 132 has V grooves
134 each having a V-shaped cross section for placing the respective
optical fibers 136 therein, the V grooves 134 being defined in an upper
surface of the ceramic substrate 132. The optical fibers 136 are disposed
in the respective V grooves 134, and held in position by the ceramic
substrate 142 and the cover 142. The second optical waveguide chip 130 has
an end face 146 polished to an optical finish such that it lies at
90.degree. with respect to the direction in which light is propagated
through the optical fibers 136.
The first optical waveguide chip 110 has an end face 124 polished to an
optical finish such that it is inclined at 62.degree. to the direction in
which light is propagated through the Ti-diffused optical waveguides 117.
The second optical waveguide chip 130 has an end face 144 polished to an
optical finish such that it is inclined at 62.degree. to the direction in
which light is propagated through the optical fibers 136.
The end face 124 of the first optical waveguide chip 110 and the end face
144 of the second optical waveguide chip 130 are held in direct contact
with each other. With such an arrangement, the Ti-diffused optical
waveguides 117 and the optical fibers 136 are directly held against, and
optically coupled to, each other, and a portion of light propagated from
the Ti-diffused optical waveguides 117 to the optical fibers 136 is
reflected into the photodiodes of the photodiode array 180 by the end
faces 124, 144.
The method of fabricating an optical component according to the third
embodiment of the present invention will be described below.
Four Ti films (not shown) each having a width of 8 .mu.m and a thickness of
300 .ANG. are formed at a pitch or spacing of 5 mm on an upper surface of
a substrate 112 of LiNbO.sub.3 having a thickness of 1 mm. Thereafter, the
Ti films are kept at a temperature of about 1000.degree. C. for 6 hours,
thereby producing four Ti-diffused optical waveguides 117 at a pitch or
spacing of 5 mm.
Then, an end face 126 of the substrate 112 of LiNbO.sub.3 is polished to an
optical finish such that it lies at 90.degree. with respect to the
direction in which light is propagated through the Ti-diffused optical
waveguides 117 (with respect to the upper surface of the substrate 112 of
LiNbO.sub.3 in this embodiment), and an end face 124 of the substrate 112
of LiNbO.sub.3 is polished to an optical finish such that it is inclined
at 62.degree. to the direction in which light is propagated through the
Ti-diffused optical waveguides 117 (to the upper surface of the substrate
112 of LiNbO.sub.3 in this embodiment). In this manner, the first optical
waveguide chip 110 is produced.
Then, a photodiode array 180 is placed on and fixed to the upper surface of
the substrate 112 of LiNbO.sub.3.
An optical fiber array 116 composed of four optical fibers 115 and having
an end connected to optical connectors (not shown) is prepared. The other
end of the optical fiber array 116 is optically adjusted and fixed to the
end face 126 of the substrate 112 of LiNbO.sub.3.
A ceramic substrate 132 having a length of 5 mm, a width of 5 mm, and a
thickness of 3 mm is prepared, and four V grooves 134 each having a
V-shaped cross section are defined centrally in the ceramic substrate 132
for accommodating four single-mode optical fibers 136 each having a
diameter of 125 .mu.m.
Then, the four optical fibers 136, which are 125 .mu.m across and 5 mm
long, are placed respectively in the V grooves 134.
Thereafter, a cover 142 having a thickness of 0.3 mm is placed on the
ceramic substrate 132 over the optical fibers 136, and the ceramic
substrate 132, the optical fibers 136, and the cover 142 are joined to
each other by a resin adhesive.
The ceramic substrate 132, the optical fibers 136, and the cover 142 which
are thus bonded jointly have an end face 144 cut and polished to an
optical finish such that the end face 144 is inclined at 62.degree. with
respect to the direction in which light is propagated through the optical
fibers 136. An opposite end 146 thereof is polished to an optical finish
such that it lies at 90.degree. with respect to the direction in which
light is propagated through the optical fibers 136. In this manner, the
second optical waveguide chip 130 is produced.
A laser diode array 172 and a lens array 174 are positioned on the side of
the end face 146 such that four laser beams 175 emitted from the
respective laser diodes 171 will be converged onto the respective optical
fibers 136 by the respective lenses 173.
The laser diodes 171 are energized to emit laser beams. While the
intensities of the emitted laser beams are being measured by the
photodiode array 180, the optical axes of the optical fibers 136 and the
Ti-diffused optical waveguides 117 are adjusted into alignment, and
thereafter the first optical waveguide chip 110 and the second optical
waveguide chip 130 are fixed to each other. In this manner, the optical
reception/transmission module 300 is produced.
Then, as shown in FIG. 4, the optical reception/transmission module 300 is
housed in a package 250, thereby completing the optical
reception/transmission module 200. Leads 76 attached to the package 250
are electrically connected to the laser diode array 172, and leads 86
attached to the package 250 are electrically connected to the photodiode
array 180. The leads 86 are connected to the leads 184 (see FIG. 7).
FIG. 8 illustrates the methods of fabricating an optical component
according to the first and second embodiments of the present invention. In
the first and second embodiments described above, the first optical
waveguide chip 10 is composed of the ceramic substrate 12, the cover 22,
and the optical fiber 16 with the optical connector 18 mounted on one end
thereof, the optical fiber 16 having a length of 2 m, longer than the
ceramic substrate 12 and the cover 22, and the second optical waveguide
chip 30 is composed of the ceramic substrate 32, the cover 42, and the
optical fiber 36 whose opposite ends terminate at the end faces 44, 46.
The end face 24 of the first optical waveguide chip 10 is inclined to the
direction of propagation of light through the optical fiber 16, and the
end face 44 of the second optical waveguide chip 30 is inclined to the
direction of propagation of light through the optical fiber 36. The end
faces 24, 44 extend substantially parallel to each other with the air
layer 60 or the Ti film 62 interposed therebetween. The photodiode module
80 is mounted on the upper surface of the cover 22 of the first optical
waveguide chip 10, and the laser diode module 70 is mounted on the end
face 46 of the second optical waveguide chip 30.
FIG. 9 illustrates a method of fabricating an optical component according
to a fourth embodiment of the present invention. In the first and second
embodiments, the photodiode module 80 is mounted on the upper surface of
the cover 22 of the first optical waveguide chip 10, and the laser diode
module 70 is mounted on the end face 46 of the second optical waveguide
chip 30. According to the fourth embodiment, no photodiode module 80 is
mounted on the upper surface of the cover 22 of the first optical
waveguide chip 10, and no laser diode module 70 is mounted on the end face
46 of the second optical waveguide chip 30. In the first and second
embodiments, the second optical waveguide chip 30 is composed of the
ceramic substrate 32, the cover 42, and the optical fiber 36 whose
opposite ends terminate at the end faces 44, 46. According to the fourth
embodiment, a second optical waveguide chip 30 is composed of a ceramic
substrate 32, a cover 42, and an optical fiber 36 having one end
terminating at an end face 44 and an opposite end projecting from an end
face 46. The other details of the fourth embodiment are the same as those
of the first and second embodiments.
FIG. 10 illustrates a method of fabricating an optical component according
to a fifth embodiment of the present invention. In the fourth embodiment
shown in FIG. 9, no photodiode module 80 is mounted on the upper surface
of the cover 22 of the first optical waveguide chip 10. According to the
fifth embodiment,.however, a photodiode module 80 is mounted on an upper
surface of a cover 22 of a first optical waveguide chip 10. The other
details of the fifth embodiment are the same as those of the fourth
embodiment.
FIG. 11 illustrates a method of fabricating an optical component according
to a sixth embodiment of the present invention. In the fifth embodiment
shown in FIG. 10, no laser diode module 70 is employed. According to the
sixth embodiment, however, a laser diode module 70 is mounted on an end of
an optical fiber 36 which projects from an end face 46. The other details
of the fifth embodiment are the same as those of the fourth embodiment.
FIG. 12 illustrates a method of fabricating an optical component according
to a seventh embodiment of the present invention. In the first and second
embodiments described above, the first optical waveguide chip 10 is
composed of the ceramic substrate 12, the cover 22, and the optical fiber
16, and the second optical waveguide chip 30 is composed of the ceramic
substrate 32, the cover 42, and the optical fiber 36. The end face 24 of
the first optical waveguide chip 10 is inclined to the direction of
propagation of light through the optical fiber 16, and the end face 44 of
the second optical waveguide chip 30 is inclined to the direction of
propagation of light through the optical fiber 36. The end faces 24, 44
extend substantially parallel to each other with the air layer 60 or the
Ti film 62 interposed therebetween.
According to the seventh embodiment, however, a first optical waveguide
chip 10 comprises a substrate 13 of LiNbO.sub.3 and a Ti-diffused optical
waveguide 17 disposed on an upper surface thereof, and a second optical
waveguide chip 30 comprises a substrate 33 of LiNbO.sub.3 and a
Ti-diffused optical waveguide 27 disposed on an upper surface thereof. An
end face 24 of the first optical waveguide chip 10 is inclined to the
direction of propagation of light through the Ti-diffused optical
waveguide 17, and an end face 44 of the second optical waveguide chip 30
is inclined to the direction of propagation of light through the
Ti-diffused optical waveguide 27. The end faces 24, 44 extend
substantially parallel to each other with an air layer 60 interposed
therebetween. In the first and second embodiments, the photodiode module
80 is mounted on the upper surface of the cover 22 of the first optical
waveguide chip 10, and the laser diode module 70 is mounted on the end
face 46 of the second optical waveguide chip 30. According to the seventh
embodiment, however, no photodiode module 80 is mounted on the first
optical waveguide chip 10, and no laser diode module 70 is mounted on the
end face 46 of the second optical waveguide chip 30. The other details of
the seventh embodiment are the same as those of the first and second
embodiments.
FIG. 13 illustrates a method of fabricating an optical component according
to an eighth embodiment of the present invention. In the seventh
embodiment shown in FIG. 12, the end faces 24, 44 extend substantially
parallel to each other with an air layer 60 interposed therebetween.
According to the eighth embodiment, end faces 24, 44 extend substantially
parallel to each other with a Ti film 62 interposed therebetween. The
other details of the eighth embodiment are the same as those of the
seventh embodiment.
FIG. 14 illustrates a method of fabricating an optical component according
to a ninth embodiment of the present invention. In the third embodiment
shown in FIG. 7, the end face 124 of the first optical waveguide chip 110
and the end face 144 of the second optical waveguide chip 130 are held in
direct contact with each other, so that the Ti-diffused optical waveguides
117 and the optical fibers 136 are held in direct contact with each other
and optically coupled to each other, and a portion of light propagated
from the Ti-diffused optical waveguides 117 to the optical fibers 136 is
reflected by the end faces 124, 144. According to the ninth embodiment,
end faces 24, 44 extend substantially parallel to each other with a Ti
film 62 interposed therebetween, so that a Ti-diffused optical waveguide
17 and an optical fiber 36 are optically coupled to each other, and a
portion of light propagated from the Ti-diffused optical waveguide 17 to
the optical fiber 36 is reflected by the end faces 24, 44. In the third
embodiment shown in FIG. 7, the photodiode array 180 is mounted on the
upper surface of the substrate 112 of LiNbO.sub.3, and the laser diode
array 172 and the lens array 174 are mounted on the end face 146 of the
second optical waveguide chip 130. According to the ninth embodiment,
however, no photodiode array 180 is mounted on the upper surface of a
substrate 13 of LiNbO.sub.3, and no laser diode array 172 and no lens
array 174 are mounted on an end face 46 of the second optical waveguide
chip 30. In the third embodiment shown in FIG. 7, the second optical
waveguide chip 130 is composed of the ceramic substrate 132, the cover
142, and optical fibers 136 whose opposite ends terminate at the end faces
144, 146. According to the ninth embodiment, the second optical waveguide
chip 30 is composed of a ceramic substrate 32, a cover 42, and an optical
fiber 36 having one end terminating at the end face 44 and an opposite end
projecting from the end face 46. The other details of the ninth embodiment
are the same as those of the third embodiment.
FIG. 15 illustrates a method of fabricating an optical component according
to a tenth embodiment of the present invention. In the ninth embodiment
shown in FIG. 14, the first optical waveguide chip 10 is composed of the
substrate 13 of LiNbO.sub.3 and the Ti-diffused optical waveguide 17
disposed on the upper surface thereof, and the optical fiber 16 is coupled
to the Ti-diffused optical waveguide 17 at the end face 26. According to
the tenth embodiment, a first optical waveguide chip 10 comprises a
ceramic substrate 12, a cover 22, and an optical fiber 16. In the ninth
embodiment shown in FIG. 14, the second optical waveguide chip 30 is
composed of the ceramic substrate 32, the cover 42, and the optical fiber
36. According to the tenth embodiment, a second optical waveguide chip 30
comprises a substrate 33 of LiNbO.sub.3 and a Ti-diffused optical
waveguide 27 disposed on the upper surface thereof, and an optical fiber
36 is coupled to the Ti-diffused optical waveguide 27 at an end face 46.
The present invention offers the following advantages:
(1) The first optical waveguide chip having the first optical waveguide is
formed and polished to an optical finish such that an end face of the
first optical waveguide chip where an end of the first optical waveguide
is exposed is inclined to the direction of propagation of light through
the first optical waveguide, and the second optical waveguide chip having
the second optical waveguide and different from the first optical
waveguide chip is formed and polished to an optical finish such that an
end face of the second optical waveguide chip where an end of the second
optical waveguide is exposed is inclined to the direction of propagation
of light through the second optical waveguide. The first and second
optical waveguides are positioned relatively to each other such that the
inclined end faces extend substantially parallel to each other with a
layer interposed therebetween which has a refractive index that is
different from the refractive index of at least one of the first and
second optical waveguides. A portion of light propagated from the first
optical waveguide to the second optical waveguide is reflected out of at
least one of the first and second optical waveguide chips by at least one
of the inclined end faces of the first and second optical waveguide chips.
An optical component thus constructed has a length smaller than a
conventional optical component which is composed of two optical fibers
fused to each other.
(2) The first optical waveguide chip having the first optical waveguide is
formed and polished to an optical finish such that an end face of the
first optical waveguide where an end of the first optical waveguide chip
is exposed is inclined to the direction of propagation of light through
the first optical waveguide, and the second optical waveguide chip having
the second optical waveguide whose refractive index differs from that of
the first optical waveguide and different from the first optical waveguide
chip is formed and polished to an optical finish such that an end face of
the second optical waveguide chip where an end of the second optical
waveguide is exposed is inclined to the direction of propagation of light
through the second optical waveguide. The first and second optical
waveguides are positioned relatively to each other such that the inclined
end faces extend substantially parallel to each other and the exposed ends
of the first and second optical waveguides are held in direct contact with
each other and optically coupled to each other. A portion of light
propagated from the first optical waveguide to the second optical
waveguide is reflected out of at least one of the first and second optical
waveguide chips by at least one of the inclined end faces of the first and
second optical waveguide chips. An optical component thus constructed has
a length smaller than a conventional optical component which is composed
of two optical fibers fused to each other.
(3) According to the present invention, the first optical waveguide is
disposed in the first optical waveguide chip, and the second optical
waveguide chip is disposed in the second optical waveguide chip, and the
first and second optical waveguides are optically coupled to each other
and light is emitted from the first optical waveguide chip and/or the
second optical waveguide chip by the inclined end faces of the first and
second optical waveguide chips. If a plurality of light paths are
required, then a plurality of first optical waveguides may be disposed in
the first optical waveguide chip, and a plurality of second optical
waveguides may be disposed in the second optical waveguide chip. As a
result, the optical component may easily be fabricated in an integrated
configuration, and reduced in size and cost.
(4) In the case where the second optical waveguide whose refractive index
differs from that of the first optical waveguide is disposed in the second
optical waveguide chip, even though the first and second optical
waveguides are positioned relatively to each other such that the exposed
ends of the first and second optical waveguides are held in direct contact
with each other and optically coupled to each other, a portion of light
propagated from the first optical waveguide to the second optical
waveguide is reflected out of at least one of the first and second optical
waveguide chips. Consequently, the first and second optical waveguide
chips can easily be positioned relatively to each other.
(5) At least one or both of the step of forming the first optical waveguide
chip having the first optical waveguide and the step of forming the second
optical waveguide chip having the second optical waveguide may comprise
the steps of placing an optical fiber in a V groove of a V-shaped cross
section or a U groove of a U-shaped cross section which is defined in the
substrate and fixing the optical fiber in the V or U groove with the
substrate and the cover. With such a process, the first optical waveguide
and/or the second optical waveguide becomes an optical fiber. Since this
optical fiber is of the same material as the optical fiber used for
transmission, these optical fibers can easily be spliced to each other
with a small optical loss.
(6) If the first optical waveguide and/or the second optical waveguide is
formed by a process including the steps of placing an optical fiber in a V
groove of a V-shaped cross section or a U groove of a U-shaped cross
section which is defined in the substrate and fixing the optical fiber in
the V or U groove with the substrate and the cover, then the optical fiber
is positioned accurately in the optical waveguide chip. Even though the
first optical waveguide and/or the second optical waveguide is an optical
fiber, since the cover is disposed over the optical fiber, a
light-detecting element for detecting light emitted out of the first
optical waveguide and/or the second optical waveguide may be disposed on
the cover. Therefore, the light-detecting element may be installed with
ease.
(7) At least one or both of the step of forming the first optical waveguide
chip having the first optical waveguide and the step of forming the second
optical waveguide chip having the second optical waveguide may comprise
the step of diffusing an impurity in a dielectric substrate to form an
optical waveguide in the dielectric substrate. With such a process, a
number of optical waveguides may easily be formed in a substrate, and may
easily be fabricated in an integrated configuration. Where the first
optical waveguide and/or the second optical waveguide is in the form of an
optical waveguide formed by diffusing an impurity in the dielectric
substrate, a light-detecting element or the like may easily be placed on
the dielectric substrate even without placing a cover on the dielectric
substrate.
(8) In the case where the inclined end faces extend substantially parallel
to each other with a layer interposed therebetween which has a refractive
index that is different from the refractive index of at least one of the
first and second optical waveguides, the layer may comprise a dielectric
or metal layer interposed between the inclined end faces, and the exposed
ends of the first and second optical waveguides may be held in direct
contact with one and other surfaces of the dielectric or metal layer. With
this arrangement, the distance between the exposed ends of the first and
second optical waveguides is determined highly accurately, and hence it is
possible to determine with accuracy an intensity of light which is
transmitted from the first optical waveguide to the second optical
waveguide and an intensity of light which is emitted out of at least one
of the first and second optical waveguide chips.
Since the dielectric or metal layer is interposed between the exposed ends
of the first and second optical waveguides, the intensity of light which
is transmitted from the first optical waveguide to the second optical
waveguide and the intensity of light which is emitted out of at least one
of the first and second optical waveguide chips can easily be controlled
by selecting a material of the dielectric or metal layer.
(9) In the case where the step of positioning the first and second optical
waveguide chips comprises the steps of defining the first and second guide
grooves in the first and second optical waveguide chips and positioning
the first and second optical waveguide chips with reference to pins
intimately held in the first and second guide grooves, the first and
second optical waveguide chips can easily be positioned relatively to each
other.
(10) In the case where the step of forming the first optical waveguide chip
having the first optical waveguide comprises the step of forming the first
optical waveguide chip having a plurality of parallel optical waveguides,
and the step of forming the second optical waveguide chip having the
second optical waveguide comprises the step of forming the second optical
waveguide chip having a plurality of parallel optical waveguides, a highly
integrated optical component can be fabricated.
Although certain preferred embodiments of the present invention has been
shown and described in detail, it should be understood that various
changes and modifications may be made therein without departing from the
scope of the appended claims.
* * * * *
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