U.S. patent application number 10/460405 was filed with the patent office on 2003-12-25 for optical semiconductor module.
This patent application is currently assigned to The Furukawa Electric Co., Ltd.. Invention is credited to Fukushima, Toru, Koseki, Takashi, Miyokawa, Jun.
Application Number | 20030235377 10/460405 |
Document ID | / |
Family ID | 27655646 |
Filed Date | 2003-12-25 |
United States Patent
Application |
20030235377 |
Kind Code |
A1 |
Miyokawa, Jun ; et
al. |
December 25, 2003 |
Optical semiconductor module
Abstract
An optical semiconductor module includes an optical
semiconductor element; an optical fiber optically coupled with the
semiconductor element; a base having an upper surface and a lower
surface; and a package. The package has a bottom plate on which the
base is mounted, a front wall having a hole through which the
optical fiber is inserted, and a rear wall opposite to the front
wall. The optical fiber and the optical semiconductor element are
mounted on the upper surface. The base has a rear face formed on an
end portion opposite to the front wall, and the rear face is
positioned above the lower surface of the base.
Inventors: |
Miyokawa, Jun; (Tokyo,
JP) ; Koseki, Takashi; (Tokyo, JP) ;
Fukushima, Toru; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
The Furukawa Electric Co.,
Ltd.
Tokyo
JP
|
Family ID: |
27655646 |
Appl. No.: |
10/460405 |
Filed: |
June 13, 2003 |
Current U.S.
Class: |
385/92 |
Current CPC
Class: |
G02B 6/4248 20130101;
G02B 6/4201 20130101; G02B 6/4256 20130101; G02B 6/4257 20130101;
G02B 6/424 20130101; G02B 6/4269 20130101; G02B 6/4277 20130101;
G02B 6/4251 20130101 |
Class at
Publication: |
385/92 |
International
Class: |
G02B 006/42 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2002 |
JP |
2002-174969 |
Claims
What is claimed is:
1. An optical semiconductor module, comprising: an optical
semiconductor element; an optical fiber optically coupled with the
semiconductor element; a base having an upper surface and a lower
surface, the optical fiber and the optical semiconductor element
being mounted on the upper surface; and a package having a bottom
plate on which the base is directly mounted, a front wall having a
hole through which the optical fiber is inserted, and a rear wall
opposite to the front wall, wherein the base has a rear face formed
on an end portion opposite to the front wall, the rear face being
positioned above the lower surface.
2. The optical semiconductor module according to claim 1, wherein
the rear face is tapered such that the rear face approaches to the
upper surface as approaching to the rear wall of the package.
3. The optical semiconductor module according to claim 1, wherein
the rear face is curved such that the rear face approaches to the
upper surface as approaching to the rear wall of the package.
4. The optical semiconductor module according to claim 1, wherein
the rear face constitutes a step.
5. The optical semiconductor module according to claim 1, wherein a
diameter of the hole in the front wall is larger than a diameter of
the hole at a position away from the front wall.
6. The optical semiconductor module according to claim 1, wherein
the package is any one of a butterfly package and a dual-in-line
package.
7. The optical semiconductor module according to claim 1, wherein
at least one of sides of a main body of the package has a length
not larger than 16 millimeter.
8. An optical semiconductor module, comprising: an optical
semiconductor element; an optical fiber optically coupled with the
semiconductor element; a base having an upper surface and a lower
surface, the optical fiber and the optical semiconductor element
being mounted on the upper surface; a package having a bottom plate
on which the base is directly mounted, and a front wall having a
hole through which the optical fiber is inserted; and a lid having
a first portion disposed above the base and a second portion facing
the hole, the first portion and the second portion of the lid being
combined with each other to cover the package.
9. The optical semiconductor module according to claim 8, wherein
the package further has a rear wall opposite to the front wall, the
rear wall being combined with the second portion of the lid.
10. The optical semiconductor module according to claim 9, wherein
the base has a rear face formed on an end portion opposite to the
front wall, the rear face being positioned above the lower
surface.
11. The optical semiconductor module according to claim 8, wherein
the rear face is tapered such that the rear face approaches to the
upper surface as approaching to the rear wall of the package.
12. The optical semiconductor module according to claim 8, wherein
the rear face is curved such that the rear face approaches to the
upper surface as approaching to the rear wall of the package.
13. The optical semiconductor module according to claim 8, wherein
the rear face constitutes a step.
14. The optical semiconductor module according to claim 8, wherein
a diameter of the hole in the front wall is larger than a diameter
of the hole at a position away from the front wall.
15. The optical semiconductor module according to claim 8, wherein
the package is any one of a butterfly package and a dual-in-line
package.
16. The optical semiconductor module according to claim 8, wherein
at least one of sides of a main body of the package has a length
not larger than 16 millimeter.
17. An optical semiconductor module, comprising: an optical
semiconductor element; an optical fiber optically coupled with the
semiconductor element; a base having an upper surface and a lower
surface, the optical fiber and the optical semiconductor element
being mounted on the upper surface; a package having a bottom plate
on which the base is mounted, and a front wall having a hole
through which the optical fiber is inserted; and a lid having a
cover portion disposed above the base, wherein at least one of the
base and the package has a means for preventing any one of a
reduction in an optical coupling efficiency between the optical
fiber and the semiconductor element; and a breakage of the optical
fiber during assembling the semiconductor module.
18. The optical semiconductor module according to claim 17, wherein
the means includes any one of a rear face that is formed on an end
portion opposite to the front wall such that the rear face is
positioned above the lower surface; and a wall portion facing the
hole, and combined with the cover portion to cover the package.
Description
BACKGROUND OF THE INVENTION
[0001] 1) Field of the Invention
[0002] The present invention relates to an optical semiconductor
module having an optical semiconductor element and an optical fiber
that are used for optical communications.
[0003] 2) Description of the Related Art
[0004] FIG. 23A is a plan view of a part of a conventional
semiconductor laser diode (hereinafter, "LD") module, and FIG. 23B
is a longitudinal cross-sectional view of the part. The LD module
includes a base 6 onto which a heat sink 3 and a carrier 5 are
soldered. On the heat sink 3, an LD element 1 and a thermistor 2
are mounted, and on the carrier 5, a photo diode (hereinafter,
"PD") element 4 is mounted. Further, a metal ferrule 7a supporting
an optical fiber 7 is fixed onto the base 6 via two support members
6a by YAG laser welding or with solder. The welding points, in the
drawings, are denoted by solid circles P.sub.wd. The optical fiber
7 is precisely aligned so as to be optically coupled with a laser
beam emitted from the LD element 1, and is fixed onto the support
member 6a.
[0005] FIG. 24 is a longitudinal cross-sectional view of the
conventional LD module, where the base 6 is accommodated within a
package 8, and is fixed onto a bottom plate 8e of the package 8.
The package 8 is sealed with a lid 9 at the upper opening, thereby
to complete the assembly of the LD module. A lensed fiber, one end
of which being formed in a spherical or a wedged shape to serve as
a lens portion, is used as the optical fiber 7 in order to ensure a
high coupling efficiency between the optical fiber 7 and the laser
beam emitted from the LD element 1. The other end of the optical
fiber 7 is led out of the package 8 through a longitudinal hole 8a
of a snout 8b prior to mounting of the base 6 onto the bottom plate
8e of the package 8. A portion between the optical fiber 7 and the
internal wall of the snout 8b is hermetically sealed with sealant S
like solder or synthetic resin.
[0006] The LD module, particularly one using the lensed fiber,
requires that the LD element 1 and the lensed fiber are coupled
with an extremely high precision, and that the optical fiber 7 and
the support member 6a are precisely positioned.
[0007] In the LD module shown in FIG. 24, the base 6 is directly
fixed onto the bottom plate 8e, with no Peltier module for cooling
interposed. The longitudinal hole 8a in FIG. 24 is formed through a
front wall 8c of the package 8 at a position far down from the
upper end of the front wall 8c. Such position of the longitudinal
hole 8a makes the mounting of the base 6 difficult.
[0008] FIG. 25 is a longitudinal cross-sectional view of the
conventional LD module in the mounting step. In the mounting step,
the base 6 is accommodated onto the bottom plate 8e, maintaining a
state that the optical fiber 7 passes through the longitudinal hole
8a. In such a situation, a position of the metal ferrule 7a holding
the optical fiber 7 is limited by the position of the longitudinal
hole 8a, causing often an interference between a lower portion of
the base 6 and a rear wall 8d of the package 8 when mounting the
base 6, depending on sizes of the package 8 and the base 6. And
while the base 6 is being mounted onto the bottom plate 8e of the
package 8 so as to avoid the interference, stress is often applied
to the optical fiber 7 and thereby the optical fiber 7 is bent,
pressed, or pulled. In this way, this stress often causes
misalignment between the LD element 1 and the optical fiber 7.
[0009] Further, in the mounting step, the optical fiber 7 is often
excessively bent at a portion A encircled by a dashed line in FIG.
25, by contact with the snout 8b. In some cases, the optical fiber
7 is coated with metal (e.g., gold), in order to facilitate the
hermetic sealing of the optical fiber 7 inside the inner space of
the snout 8b with solder S or other sealant, or in order to
facilitate the soldering of the optical fiber 7 to the base 6. Such
metal-coated optical fibers have a minimum allowable bending
curvature radius larger than that of non-coated optical fibers and
are more repulsive against the bending deformation. Therefore, the
optical fiber 7 needs to be handled so as not to be bent too
much.
[0010] The similar situation may be present not only in optical
semiconductor modules in general of butterfly-type, including
receiver modules (hereinafter, "PD modules") having a PD element
mounted on the base 6, but also in the LD module of so-called DIL
(Dual In Line) type which utilizes a small-sized package.
SUMMARY OF THE INVENTION
[0011] The optical semiconductor module according to one aspect of
the present invention includes an optical semiconductor element; an
optical fiber optically coupled with the semiconductor element; a
base having an upper surface and a lower surface, the optical fiber
and the optical semiconductor element being mounted on the upper
surface; and a package having a bottom plate on which the base is
directly mounted, a front wall having a hole through which the
optical fiber is inserted, and a rear wall opposite to the front
wall, wherein the base has a rear face formed on an end portion
opposite to the front wall, the rear face being positioned above
the lower surface.
[0012] The optical semiconductor module according to another aspect
of the present invention includes an optical semiconductor element;
an optical fiber optically coupled with the semiconductor element;
a base having an upper surface and a lower surface, the optical
fiber and the optical semiconductor element being mounted on the
upper surface; a package having a bottom plate on which the base is
directly mounted, and a front wall having a hole through which the
optical fiber is inserted; and a lid having a first portion
disposed above the base and a second portion facing the hole, the
first portion and the second portion of the lid being combined with
each other to cover the package.
[0013] The other features and advantages of the present invention
are specifically set forth in or will become apparent from the
following detailed descriptions of the invention when read in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a longitudinal cross-sectional view of a LD module
according to a first embodiment of the present invention;
[0015] FIG. 2 is a top plan view of a package of the LD module
shown in FIG. 1;
[0016] FIG. 3 is a longitudinal cross-sectional view of a part of
the LD module shown In FIG. 1;
[0017] FIG. 4 is a longitudinal cross-sectional view of the LD
module in the mounting step;
[0018] FIG. 5A and FIG. 5B are longitudinal cross-sectional views
of other examples of a base of the LD module;
[0019] FIG. 6A is a top plan view of other example of the base, and
FIG. 6B is a longitudinal cross-sectional view of the base shown in
FIG. 6A;
[0020] FIG. 7 is a longitudinal cross-sectional view of a LD module
according to one example of a second embodiment of the present
invention;
[0021] FIG. 8 is a longitudinal cross-sectional view of the LD
module shown in FIG. 7 in the mounting step;
[0022] FIG. 9 is a longitudinal cross-sectional view of a LD module
according to another example of the second embodiment in the
mounting step;
[0023] FIG. 10 is a longitudinal cross-sectional view of a LD
module according to still another example of the second embodiment
in the mounting step;
[0024] FIG. 11 is a longitudinal cross-sectional view of a LD
module according to still another example of the second embodiment
in the mounting step;
[0025] FIG. 12 is a longitudinal cross-sectional view of a LD
module according to still another example of the second embodiment
in the mounting step;
[0026] FIG. 13 is a longitudinal cross-sectional view of a PD
module according to a third embodiment of the present
invention;
[0027] FIG. 14A is a top plan view of one example of a base used
for the PD module shown in FIG. 13, and FIG. 14B is a side view of
the base shown in FIG. 14A;
[0028] FIG. 15 is a longitudinal cross-sectional view of the PD
module shown in FIGS. 14A and 14B in the mounting step;
[0029] FIG. 16 is a side view of a LD module according to a fourth
embodiment of the present invention;
[0030] FIG. 17 is a top plan view of the LD module shown in FIG.
16;
[0031] FIG. 18 is a longitudinal cross-sectional view of a LD
module according to a fifth embodiment of the present
invention;
[0032] FIG. 19 is a longitudinal cross-sectional view of the LD
module shown in FIG. 18 in the mounting step;
[0033] FIG. 20 is a longitudinal cross-sectional view of another
example of the LD module according to the fifth embodiment, having
a different package from that shown in FIG. 18;
[0034] FIG. 21 is a longitudinal cross-sectional view of still
another example of the LD module according to the fifth embodiment,
having a different form of a snout from that shown in FIG. 18;
[0035] FIGS. 22A to 22C are longitudinal cross-sectional views of
still other examples of the LD module according to the fifth
embodiment, having different forms of a snout and different forms
of a base from the LD module shown in FIG. 18;
[0036] FIG. 23A is a plan view of a part of a conventional LD
module, and FIG. 23B is a side view of the part;
[0037] FIG. 24 is a longitudinal cross-sectional view of the
conventional LD module; and
[0038] FIG. 25 is a longitudinal cross-sectional view of the
conventional LD module in the mounting step.
DETAILED DESCRIPTION
[0039] Exemplary embodiments of the optical semiconductor module
relating to the present invention will be explained in detail below
with reference to the accompanying drawings. In the following
embodiments, constituent parts identical with those of the LD
module shown in FIG. 24 are designated with like reference
symbols.
[0040] An optical semiconductor module according to a first
embodiment of the present invention is an LD module. FIG. 1 is a
longitudinal cross-sectional view of the LD module. This LD module
10 differs from the conventional LD module shown in FIG. 24, in
that a base 11 is fixed onto the bottom plate 8e instead of the
base 6. On the base 11 are provided, the heat sink 3 mounting
thereon the LD element 1 and the thermistor 2, the carrier 5
mounting thereon the PD element 4, and two pieces of support
members 11a supporting the metal ferrule 7a holding the optical
fiber 7. The metal ferrule 7a is fixed to the base 11 through the
two support members 11a by YAG laser-welding or soldering. The
optical fiber 7 is arranged to pass through the longitudinal hole
8a of the snout 8b. The portion between the optical fiber 7 and the
internal wall of the snout 8b is hermetically sealed with a sealant
S like solder. The package 8 is sealed with the lid 9 at the upper
opening. The package 8 also has a front wall 8c and a rear wall 8d
that faces the front wall 8c.
[0041] FIG. 2 is a top plan view of the package 8. The package 8 is
of a butterfly type having a plurality of leads L.sub.d protruding
from the package 8 at both sides. The snout 8b is covered with a
rubber covering B.sub.g. A part of the optical fiber 7 that is led
out of the package 8 is protected by a protective tube T.sub.g. The
package 8 has a length L not larger than 16 millimeter, a width W
not larger than 10 millimeter, and a height H not larger than 8
millimeter, as shown in FIGS. 1 and 2.
[0042] FIG. 3 is a longitudinal cross-sectional view of a part of
the LD module shown in FIG. 1, and specifically illustrates the
base 11. The base 11 differs from the base 6 shown in FIGS. 23A,
23B, 24, and 25, in the shape of the rear end portion to be faced
to the rear wall 8d of the package 8. As shown in FIG. 3, the base
11 has a rear end portion E having an upper edge F.sub.U and an
lower edge F.sub.L. The lower edge F.sub.L is positioned nearer to
the front end portion of the base 11 than the upper edge F.sub.U.
In other words, the base 11 has a taper 11b that is inclined from
the vicinity of the upper edge F.sub.U toward the lower edge
F.sub.L, at the rear end portion E. As a result, the formation of
the taper 11b is equivalent to elimination of the rear lower corner
of the base 11.
[0043] FIG. 4 is a longitudinal cross-sectional view of the LD
module in the mounting step. When the base 11 is mounted into the
package 8 in a direction of an arrow mark shown in the FIG. 4, no
interference occurs between the base 11 and the rear wall 8d of the
package 8. This is because of the elimination of the rear lower
corner of the base 11 by the taper 11b. Therefore, the base 11 can
be easily mounted onto the bottom plate 8e of the package 8.
Consequently, no significant misalignment between the LD element 1
and the optical fiber 7 can occur in the mounting step and it is
possible to suppress a reduction in the coupling efficiency between
the laser beam emitted from the LD element 1 and the optical fiber
7.
[0044] Moreover, the prevention of interference between the base 11
and the rear wall 8d results in a prevention of an excessive bend
of the optical fiber 7 at the portion A encircled by the dashed
line in FIG. 4. Consequently, the optical fiber 7 can be maintained
at a large radius of bending curvature during the mounting step
into the package 8, and is free from a breakage arising from the
excessive bending.
[0045] The shape of the rear end portion E of the base 11 is not
limited to that shown in FIG. 3. The rear end portion E may be
formed into various shapes to avoid an interference against the
rear wall 8d in the mounting step. For example, the rear end
portion may be formed into a curved face 11c with a curvature
radius of r as shown in FIG. 5A, or a step 11d with a height h2 and
a length L1 as shown in FIG. 5B.
[0046] In the LD module 10 according to the present embodiment, the
base 11 is mounted into the package 8 in the state that the rear
end portion E is slightly inclined from a horizontal state such
that the optical fiber 7 led from the snout 8b to the outside of
the package is not excessively bent. When the base 11 is formed
Into the taper 11b, for example, a height h1 of the base 11 from
its bottom surface to a line of intersection between the taper 11b
and the rear end surface of the base 11 is set to a range of about
0.4.ltoreq.h1/t.ltoreq.1.0, where t is a thickness of the base 11,
as shown in FIG. 3. While an inclination angle of the taper face
11b is suitably set according to a size of the package 8, an
inclination angle .theta. within a side cross-sectional surface of
the base 11 parallel to an optical axis is set to a range of about
20.degree..ltoreq..theta..ltoreq.60.degree.. On the other hand,
when the base 11 is formed to have the curved face 11c having a
cylindrical surface or the step 11d, the radius r of the
cylindrical surface (see FIG. 5A) or the height h2 and the length
L1 of the step (see FIG. 5B) are set to ranges of about
0.4.ltoreq.r/t, L1/t.ltoreq.1.0, and 0.4.ltoreq.h2/t.ltoreq.0.7,
where t is a thickness of the base 11.
[0047] The optical fiber 7 may be directly fixed with solder Sd,
onto a support member 11e that is fixed to the base 11, with no
metal ferrule 7a employed, as shown in FIGS. 6A and 6B. It is
needless to mention that the rear end portion E of the base 11 may
also be formed into the curved face 11c or the step 11d as shown in
FIG. 5A or FIG. 5B. The support member 11e may be made of nonmetal
such as ceramic, for example. When the optical fiber 7 is fixed
onto the support member 11e with an adhesive or a synthetic resin,
an optical fiber of which external periphery is not metal-coated
may also be used.
[0048] FIG. 7 is a longitudinal cross-sectional view of an LD
module according to the second embodiment of the present invention.
The LD module 15 differs from the conventional LD module, in the
shape of its package. The LD module 15 is configured as an optical
semiconductor module having a butterfly-type package. As shown in
FIG. 7, a snout 108b of a package 108 consists of a first part
108b.sub.1 and a second part 108b.sub.2. The second part 108b.sub.2
has a larger diameter then that of the first part 108b.sub.1, and
is positioned between the first part 108b.sub.1 and a front wall
108c of the package 108. These first part 108b.sub.1 and the second
part 108b.sub.2 have a longitudinal hole 108a through them, for
guiding the optical fiber 7 to the outside. The longitudinal hole
108a consists of a first longitudinal hole 108a.sub.1 of the first
part 108b.sub.1, and a second longitudinal hole 108a.sub.2 of the
second part 108b.sub.2. The longitudinal hole 108a is, concretely,
formed such that an upper boundary F.sub.UI of the second
longitudinal hole 108a.sub.2 is located higher than an upper
boundary F.sub.UO of the first longitudinal hole 108a.sub.1. As a
result, the optical fiber 7, when led to the outside of the package
108 through the longitudinal hole 108a, is prevented from being
brought into contact with the internal surface of the second
longitudinal hole 108a.sub.2. Therefore, an excessive bending
deformation of the optical fiber 7 is suppressed.
[0049] Consequently, in the LD module 15, in the mounting step of
the base 11 into the package 108, it is possible not only to
maintain a state of a large bending curvature radius of the optical
fiber 7 by the taper 11b but also to prevent the optical fiber 7
from being brought into contact with the internal surface of the
second longitudinal hole 108a.sub.2 of the second part 108b.sub.2
of the snout 108.sub.b, as shown in FIG. 8. Consequently, in the LD
module 15, it possible to prevent an excessive bending deformation
of the optical fiber 7 arising from the interference between the
optical fiber 7 and the internal surface of the longitudinal hole
108a that would otherwise occur at a portion A encircled by a
dashed line.
[0050] The LD module 15 according to the second embodiment has an
effect that the second part 108b.sub.2 provided in the snout 108b
prevents the optical fiber 7 from being excessively bent, in
addition to the effect that the taper 11b of the base 11
facilitates the mounting of the base 11 into the package 108.
Therefore, in the LD module 15, it is possible to suppress a
breakage of the metal-coated optical fiber 7 in the mounting step
more surely than in the LD module 10 according to the first
embodiment. Note that the longitudinal hole 108a may have a
plurality of diameters so as to have three or more steps. The snout
108b may take a shape other than that shown in FIG. 7, as far as it
is possible to suppress the bending deformation of the optical
fiber 7 in the mounting step. For example, the second part
108b.sub.2 of the snout 8b is inclined toward the upper end portion
of the front wall 108c, and the upper boundary F.sub.UI of the
longitudinal hole 108a is positioned higher than the upper boundary
F.sub.UO.
[0051] A package 208 may be used in place of the package 108 (see
FIG. 9). The package 208 has a front wall 208c, a rear wall 208d, a
bottom plate 208e, and a snout 208b. An external diameter of the
snout 208b is uniform along the longitudinal direction. The snout
208b has a longitudinal hole 208a whose diameter is linearly small
toward the outside. In other words, the longitudinal hole 208a has
taper at its internal surface along the longitudinal direction. The
taper may not necessarily be formed over the entire of the internal
surface along its longitudinal direction but may be formed at least
on a part thereof. For example, the taper is formed on only a part
of the internal surface near the front wall 208c.
[0052] Further, a package 308 may be used in place of the package
108 (see FIG. 10). The package 308 has a front wall 308c, a rear
wall 308d, a bottom plate 308e, and a snout 308b having a
longitudinal hole 308a. The snout 308b has a first part 308b.sub.1
and a second part 308b.sub.2. A part of the longitudinal hole 308a
on the first part 308b.sub.1 has a uniform diameter along the
longitudinal direction, and a part of longitudinal hole 308a on the
second part 308b.sub.2 has diameter that is linearly small toward
the first part 308b.sub.1. External diameters of the snout 308b are
values corresponding to the diameters of the longitudinal hole 308a
of the first part 308b.sub.1 and of the second part 308b.sub.2.
[0053] Further, a package 408 may be used in place of the package
108 (see FIG. 11). The package 408 has a front wall 408c, a rear
wall 408d, a bottom plate 408e, and a snout 408b having a
longitudinal hole 408a. The external diameter of snout 408b and the
diameter of the longitudinal hole 408a are linearly small from the
front wall 408c toward the outside of the package 408.
[0054] Furthermore, a package 508 may be used in place of the
package 108 (see FIG. 12). The package 508 has a front wall 508c, a
rear wall 508d, a bottom plate 508e, and a snout 508b having a
longitudinal hole 508a. The external and internal faces of snout
508b are curved such that an external diameter of the snout 508b
and a diameter of the longitudinal hole 508a become gradually small
from the front wall 508c toward the outside of the package 508.
[0055] FIG. 13 is a longitudinal cross-sectional view of a PD
module according to a third embodiment of the present invention.
The PD module differs from the LD module shown in FIG. 1, in that
the base 11 having the tapered rear end portion E is used for the
PD module. The PD module 20 is an optical semiconductor module
having a butterfly-type package. A carrier 5 on which a PD element
4 is provided and a metal support member 11e are mounted on the
base 11. The metal support member 11e is fixed onto the base 11
with solder. The support member 11e may be made of nonmetal, such
as ceramic, for example. The optical fiber 7 coated with metal is
directly fixed onto the metal support member 11e with solder Sd, as
shown in FIGS. 13, 14A, and 14B. A portion between the optical
fiber 7 and the internal wall of the snout 8b is hermetically
sealed with a sealant S like solder or synthetic resin. An upper
portion of the package 8 is sealed with a lid 9.
[0056] The base 11 has the rear end portion E with the tapered face
11b, like that shown in FIG. 1. The PD module 20 is formed as
explained above. Therefore, as shown in FIG. 15, in the mounting
step of the base 11 into the package 8, it is possible to prevent
an interference between the base 11 and the rear wall 8d of the
package 8. Accordingly, the base 11 can be easily mounted into the
package 8. Consequently, in the mounting step, there occurs no
misalignment between the PD element 4 and the optical fiber 7. As a
result, it becomes possible to avoid a reduction in the optical
coupling efficiency between the PD element 4 and the optical fiber
7.
[0057] Since the rear end portion E of the base 11 has a taper, the
optical fiber 7 is free from excessive bending at a portion A
encircled by a dashed line in FIG. 15 when mounting the base 11
into the package 8 with the optical fiber 7 being inserted through
the longitudinal hole 8a. Since the optical fiber 7 maintains a
state of a large bending curvature radius, a breakage of the
optical fiber 7 is avoided.
[0058] The rear end portion E of the base 11 may be formed into
various shapes, such as, for example, the curved face 11c or the
step 11d as shown in FIG. 5A or FIG. 5B.
[0059] FIG. 16 is a longitudinal cross-sectional view of a package
of a LD module according to a fourth embodiment. The LD module 30
differs from the LD module 10 according to the first embodiment in
the type of package. Concretely, in the LD module 30, a package 608
closed with a lid 609 is a DIL-type. FIG. 17 is a top plan view of
the package of the LD module 30.
[0060] As shown in FIGS. 16 and 17, the LD module 30 has a
plurality of leads Ld extending downward from the side surfaces of
the package 608. An unillustrated snout of the package 608 is
covered with a rubber covering B.sub.g, and a part of the optical
fiber 7 that is led out of the package 608 is protected by a
protective tube T.sub.g. The package 608 has a length L not larger
than 16 millimeter, a width W not larger than 10 millimeter, and a
height H not larger than 8 millimeter. The base 11 shown in one of
FIG. 3 and FIGS. 5A to 6B is mounted into the package 8.
[0061] Therefore, although the LD module 30 is very small, the base
11 can be easily mounted into the package 608. Consequently, it is
possible to avoid a reduction in the coupling efficiency between
the laser beam emitted from the LD element 1 to the optical fiber
7.
[0062] Since a rear end portion E of the base 11 is formed into the
taper 11b, a curved face 11c, or a step 11d, the optical fiber 7 is
not excessively bent in the mounting step. As a result, the optical
fiber 7 can be maintained at a large bending curvature radius, and
thus free from breakage in the mounting step.
[0063] Note that if a longitudinal hole through which the optical
fiber 7 passes is formed to have a larger size at the inside than
at the outside of the package 608 as shown in FIGS. 7 to 12, it is
possible to more surely suppress an excessive bending deformation
of the optical fiber 7 in the mounting step, thereby to surely
avoid a breakage of the optical fiber 7.
[0064] FIG. 18 is a longitudinal cross-sectional view of a LD
module according to a fifth embodiment of the present invention.
The LD module 35 differs from the optical semiconductor modules
according to the first through the fourth embodiments, in a base
and a lid of a package. In the first through the fourth embodiment,
the rear end portion of the base 11 or a longitudinal hole 708a
provided in the snout 708b of a package 708 was processed in
various ways. On the other hand, in the LD module 35, a
butterfly-type or DIL-type package 708 fails to have a rear wall at
a side opposite to the snout 708b, or it has a rear wall with at
least a part thereof removed.
[0065] For example, in the LD module 35 shown in FIG. 18, the
butterfly-type or DIL-type package 708 has no rear wall opposite to
a front wall 708c. Instead, the wall that faces the front wall 708c
is replaced by a perpendicular plate 709a that is integrated with a
lid 709.
[0066] Therefore, as shown in FIG. 19, the package 708 is open at
the rear side thereof (i.e., at the left side in FIG. 18 and FIG.
19) when mounting the base 11 onto the bottom plate 708e. Hence, it
is possible to insert the base 11 into the package 708 from the
left without causing interference of the optical fiber 7 with the
inner wall of the longitudinal hole 708a at its end exposed on the
front wall 708c. It is substantially unnecessary to curve the
optical fiber 7 at a portion A of the package 708 encircled by a
dashed line. Since the optical fiber 7 can be maintained at a large
bending curvature radius, a breakage of the optical fiber 7 is
avoided. Further, it becomes possible to avoid a reduction in the
optical coupling efficiency between the LD element 1 and the
optical fiber 7.
[0067] Another package and lid in place of the package 708 and the
lid 709 may be used if the package is open at the side opposite to
the snout before closing with the lid. For example, as shown in
FIG. 20, a package 808 in place of the package 708 may be used for
an LD module 45, wherein the upper portion of a rear wall 808d
opposite to a front wall 808c is removed, and a perpendicular plate
809b provided integrally with the lid 809 may be located at this
removed portion.
[0068] Since the optical fiber 7 can be inserted horizontally in
this embodiment, a snout may be formed to have a longitudinal hole
908a with a diameter that is uniform in the longitudinal direction,
as shown in FIG. 21.
[0069] These LD modules shown in FIGS. 20 and 21 make the mounting
step easy, without substantially bending the optical fiber 7, in a
similar manner to that shown in FIG. 19. Further, the rear end
portion E of the base 11 may have a taper, a curved face or a step,
like that shown in FIG. 3, FIG. 5A, or FIG. 5B, whereby it is
possible to prevent the optical fiber 7 from being excessively bent
due to the interference between the rear end portion E of the base
11 and the residual rear wall 808d, in the mounting step.
[0070] In addition, a snout of the package may have forms other
than those shown in FIGS. 18 and 21. For example, LD modules 65,
75, and 85 shown in FIGS. 22A to 22C have packages 1008, 1108, and
1208, respectively. A snout 1008b of the package 1008 shown in FIG.
22A corresponds to the snout 208b shown in FIG. 9, a snout 1108b of
the package 1108 shown in FIG. 22B corresponds to the snout 308b
shown in FIG. 10, and a snout 1208b of the package 1208 shown in
FIG. 22C corresponds to the snout 408b shown in FIG. 11.
[0071] These package may be used for not only the LD module but
also the PD module according to the third embodiment.
[0072] Advantages derived from the present invention may include
one or more of the following.
[0073] According to one or more embodiment of the present
invention, it is easy to mount the base into the package.
[0074] According to one or more embodiment of the present
invention, it is possible to avoid a reduction in the coupling
efficiency between the optical fiber and the optical semiconductor
element.
[0075] According to one or more embodiment of the present
invention, it is possible to prevent the optical fiber from being
excessively bent, thereby to maintain the state of a large radius
of bending curvature and prevent a breakage of the optical
fiber.
[0076] Although the invention has been described with respect to a
specific embodiment for a complete and clear disclosure, the
appended claims are not to be thus limited but are to be construed
as embodying all modifications and alternative constructions that
may occur to one skilled in the art which fairly fall within the
basic teaching herein set forth.
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