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Description  |
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TECHNICAL FIELD
The present invention relates to an optical parallel transmission
transmitter/receiver used for optical communication, and an optical module
substrate having optical elements (light-receiving element/light-emitting
elements) and optical fibers.
BACKGROUND ART
Along with an increase in required transmission capacity, the optical
parallel data transmission technology for optical communication systems is
becoming promising. An optical communication system using the optical
parallel data transmission technology is divided into three sections: a
transmission section, optical fiber transmission line, and reception
section. In the transmission section, a plurality of electronic signals
forming a bit sequence are input, subjected to signal processing, waveform
shaping, and amplification, and output as optical signals through a
current driving circuit and light-emitting element. In the reception
section, the optical signals are converted into electrical signals by
light-receiving elements, and the signals are subjected to amplification
and signal processing to restore the original electrical signal bit
sequence (Latest Materials of Optical Communication Technology III,
"Optical parallel Data Transmission Scheme and Hardware Configuration",
pp. 191-192).
To realize an optical communication system using the optical parallel data
transmission scheme, it is necessary to 1 accurately and easily align the
optical axes of an optical element array and optical fiber array and fix
them, and 2 hermetically seal the optical element array which readily
degrades due to a change in humidity or temperature. A technique is known
for this purpose in which a bundle fiber is inserted between a plurality
of optical elements and a plurality of optical fibers to optically couple
the optical elements to the optical fibers (Japanese Patent Laid-Open No.
5-188250).
Additionally, as described in transactions "the 1995 IEICE Conference
C-185", a structure is known in which a V-groove is formed in the upper
surface of a silicon substrate, a light-emitting element is positioned and
fixed at a predetermined position on the distal end side of the V-groove,
and an optical fiber is arranged in the V-groove, thereby matching the
optical axes of the optical fiber and light-emitting element.
From the viewpoint of facilitation and automation of the manufacturing
process, a structure has been proposed in which optical coupling to
light-emitting elements or light-receiving elements is achieved using a
ferrule in which optical fiber strands are inserted and fixed (Japanese
Patent Application No. 9-83004).
As an element technique for optical parallel transmission, for example,
Japanese Patent Laid-Open No. 7-209556 discloses an optical
transmission/reception module which integrates an LD (Laser Diode) array,
PD (PhotoDiode) array, optical fiber array for optically coupling the LD
array and PD array, LD IC, and PD IC. In this optical
transmission/reception module, to facilitate alignment between the LD
array, the PD array, and the optical fiber array, an optical module
substrate made of silicon and having a plurality of V-grooves is used, and
the optical fiber is formed by inserting a plurality of optical fibers
into the V-grooves in the optical module substrate. Silicon is used for
the optical module substrate because working of V-grooves can be easily
and accurately realized.
DISCLOSURE OF THE INVENTION
However, when a plurality of optical fibers and a plurality of optical
elements (light-receiving elements or light-emitting elements) are to be
optically coupled using the conventional system, operation becomes hard.
For, e.g., a 12-fiber array, operation is greatly complicated unless shift
due to rotation is taken into consideration, unlike a case wherein a
single optical fiber is connected to an optical element.
In addition, when not only an optical fiber array but also a light-emitting
element array (e.g., a laser array) or light-receiving element array is
mounted on an optical module substrate, the alignment operation is to be
further facilitated, and the size of light-emitting module or
light-receiving module is to be reduced, the optical module substrate
according to the prior art has the following problems.
A laser beam emitted from each of a plurality of exit regions of a laser
array diverges to some extent. For this reason, when the laser array is
mounted on the mounting surface of an optical module substrate, the laser
beam emitted from each exit region is partially reflected by the mounting
surface of the optical module substrate. As a consequence, the coupling
efficiency of the optical fibers of the optical fiber array lowers, and
light reflected by the mounting surface generates noise.
Leakage light from a reflection region opposing each of the plurality of
exit regions is also reflected by the mounting surface. As a consequence,
the light reflected by the mounting surface generates noise.
When a light-emitting element array or light-receiving element array is to
be mounted on an optical module substrate, normally, printed
interconnections for electrically connecting the light-emitting element
array and driving circuit and the like, or the light-receiving element
array and amplification circuit and the like must be formed on the optical
module substrate. Especially, when the optical module substrate is formed
from a conductive material such as silicon, interconnections cannot be
directly formed on the surface by metallizing. hence, an insulating film
is formed on the surface, and interconnections are formed on this
insulating film. With this arrangement, however, operation errors occur in
the light-emitting module due to the parasitic capacitance generated
between the interconnections and the optical module substrate through the
insulating film, or noise is generated in the light-receiving module.
It is an object of the present invention to provide a structure capable of
easily realizing operation of optically coupling a plurality of optical
fibers and a plurality of optical elements. It is another object of the
present invention to provide an optical module substrate which prevents
any operation error of a light-emitting module or reduce noise in a
light-receiving module.
In order to achieve the above object, according to the present invention,
there is provided an optical parallel transmission receiver in which a
plurality of light-receiving elements and a plurality of optical fibers
are optically coupled via guide pins, characterized by comprising a pair
of guide pins, fiber holding means (e.g., a ferrule) for holding the pair
of guide pins in parallel and holding the plurality of optical fibers
(e.g., a tape-like optical fibers) between the pair of guide pins at a
predetermined interval, and light-receiving element holding means for
holding the plurality of light-receiving elements (e.g., a light-receiving
element array) between the pair of guide pins and holding one end of each
of the pair of guide pins so as to make a plane including light-receiving
surfaces of the light-receiving elements perpendicular to longitudinal
axes of the guide pins, wherein the fiber holding means and the
light-receiving element holding means are integrally held by resin
molding.
There is also provided an optical parallel transmission transmitter in
which a plurality of light-emitting elements and a plurality of optical
fibers are optically coupled via guide pins, characterized by comprising a
pair of guide pins, fiber holding means for holding the pair of guide pins
in parallel and holding the plurality of optical fibers between the pair
of guide pins at a predetermined interval, and light-emitting element
holding means for holding the plurality of light-emitting elements between
the pair of guide pins and holding one end of each of the pair of guide
pins so as to align optical axes of the light-emitting elements with core
axes of the optical fibers, wherein the fiber holding means and the
light-emitting element holding means are integrally held by resin molding.
According to the present invention, there is also provided an optical
parallel transmission receiver in which a plurality of light-receiving
elements and a plurality of optical fibers are optically coupled via a
pair of guide pins, characterized by comprising light-receiving element
holding means for holding the plurality of light-receiving elements and
holding one end of each of the pair of guide pins so as to make
light-receiving surfaces of the light-receiving elements cross core axes
of the optical fibers, wherein the light-receiving element holding means
is formed from an insulator.
The light-receiving element holding means may comprise a light-receiving
element array in which the plurality of light-receiving elements are
arranged in an array, a preamplifier IC connected to the light-receiving
element array and including a plurality of reception circuits, and a
heat-conductive lead frame which is in contact with the preamplifier IC at
one part and has a heat dissipation portion formed at the other part.
The light-receiving element holding means may comprise a guide pin holding
portion for holding the guide pins, a first holding portion for holding
the light-receiving element array, and a second holding portion for
holding the preamplifier IC, the first holding portion may be positioned
with reference to the guide pin holding portion, and when the
light-receiving element array is held by the first holding portion, the
light-receiving element array may be positioned with respect to the guide
pins to be inserted to the guide pin holding portion.
The light-receiving element holding means may comprise a first plate member
and a second plate member, which sandwich the lead frame, the first plate
member having a pair of through holes which form the guide pin holding
portions, and a pair of opening portions which expose part of the lead
frame and form the first holding portion and the second holding portion.
The light-receiving element array may comprise back-incident-type
light-receiving elements each having a light-receiving surface on an
opposite side of a surface having an electrode connected to the
preamplifier IC, the first holding portion may have an opening extending
to a back side of the light-receiving element holding means, the
back-incident-type light-receiving elements may be arranged to make the
light-receiving surfaces expose to the back side of the light-receiving
element holding means, and the plurality of optical fibers may be
optically coupled to the light-receiving surfaces of the
back-incident-type light-receiving elements through the pair of guide pins
on the back side of the light-receiving element holding means.
According to the present invention, there is provided an optical parallel
transmission transmitter in which a plurality of light-emitting elements
and a plurality of optical fibers are optically coupled via a pair of
guide pins, comprising light-emitting element holding means for holding
the plurality of light-emitting elements and holding one end of each of
the pair of guide pins so as to arrange optical axes of the light-emitting
elements and core axes of the optical fibers, wherein the light-emitting
element holding means may be formed from an insulator.
The light-emitting element holding means may comprise a light-emitting
element array in which the plurality of light-emitting elements are
arranged in an array, a driver IC array connected to the light-emitting
element array and having a plurality of driving circuits, and a
heat-conductive lead frame which is in contact with the driver IC array at
one part and has a heat dissipation portion formed at the other part.
The light-emitting element holding means may comprise a guide pin holding
portion for holding the guide pins, a first holding portion for holding
the light-emitting element array, and a second holding portion for holding
the driver IC array, and a light-receiving element may be arranged between
the first holding portion and the second holding portion.
The light-emitting element holding means may comprise a first plate member
and a second plate member, which sandwich the lead frame, the first plate
member having a pair of grooves which form the guide pin holding portion,
and a pair of opening portions which expose part of the lead frame and
form the first holding portion and the second holding portion.
The light-emitting element array may be mounted faceup on the lead frame
via an insulating submount.
The lead frame may be separated into two parts which are held by the first
plate member and the second plate member while being spaced apart at a
predetermined interval, and the light-emitting element array may be
mounted on one part of the lead frame while the driver IC array may be
mounted on the other part of the lead frame.
The light-emitting element holding means may comprise a guide pin holding
portion for holding the guide pins on one surface, a first holding portion
for holding the light-emitting element array, and a second holding portion
for holding the driver IC array, and the driver IC array having a
plurality of driving circuits may be in contact with the light-emitting
element holding means.
According to the present invention, there is also provided an optical
module substrate for mounting a laser array having a plurality of emission
regions, and an optical fiber array formed by arraying a plurality of
optical fibers optically coupled to the plurality of emission regions,
respectively, characterized in that a groove portion is formed in a
mounting surface for mounting the laser array at a portion corresponding
to each of the plurality of emission regions of the laser array.
When the groove portion is formed in the mounting surface for mounting the
laser array at a portion corresponding to each emission region, reflection
of a laser beam emitted from the emission region by the mounting surface
is reduced.
According to the present invention, there is provided an optical module
substrate for mounting a laser array having a plurality of emission
regions, and an optical fiber array formed by arraying a plurality of
optical fibers optically coupled to the plurality of emission regions,
respectively, which may be characterized in that a groove portion is
formed in a mounting surface for mounting the laser array at a portion
corresponding to each of a plurality of reflection regions respectively
opposing the plurality of emission regions of the laser array.
When the groove portion is formed in the mounting surface for mounting the
laser array at the portion corresponding to each reflection region,
reflection of leakage light leaking from the reflection region by the
mounting surface is reduced.
According to the present invention, there is also provided an optical
module substrate for mounting a laser array having a plurality of emission
regions, and an optical fiber array formed by arraying a plurality of
optical fibers optically coupled to the plurality of emission regions,
respectively, which may be characterized in that a groove portion is
formed in a mounting surface for mounting the laser array at a portion
corresponding to each of the plurality of emission regions of the laser
array and a portion corresponding to each of a plurality of reflection
regions respectively opposing the plurality of emission regions of the
laser array.
When the groove portion is formed in the mounting surface for mounting the
laser array at the portion corresponding to each emission region,
reflection of a laser beam emitted from the emission region by the
mounting surface is reduced. In addition, when the groove portion is
formed in the mounting surface for mounting the laser array at the portion
corresponding to each reflection region, reflection of leakage light
leaking from the reflection region by the mounting surface is reduced.
According to the present invention, there is also provided a light-emitting
module characterized by comprising a laser array having a plurality of
emission regions, an optical fiber array formed by arraying a plurality of
optical fibers optically coupled to the plurality of emission regions,
respectively, an optical module substrate for mounting the laser array and
the optical fiber array, a driving circuit for driving the laser array,
and a base for mounting the optical module substrate and the driving
circuit, wherein the optical module substrate comprises any one of the
above optical module substrates.
When any one of the above optical module substrates is used, reflection of
a laser beam emitted from the emission region of the laser array by the
mounting surface is reduced, or reflection of leakage light leaking from
the reflection region of the laser array by the mounting surface is
reduced.
According to the present invention, there is also provided an optical
module substrate for mounting a light-emitting element array formed by
arraying a plurality of light-emitting elements and an optical fiber array
formed by arraying a plurality of optical fibers optically coupled to the
plurality of light-emitting elements, respectively, characterized in that
the optical module substrate is formed from an insulating ceramic.
When the optical module substrate is formed from an insulating material, no
insulating film need be formed between printed interconnections and the
optical module substrate, and a parasitic capacitance is prevented. In
addition, when the optical module substrate is formed from a ceramic, the
workability and working accuracy are ensured.
According to the present invention, there is also provided an optical
module substrate for mounting a light-receiving array formed by arraying a
plurality of light-receiving elements and an optical fiber array formed by
arraying a plurality of optical fibers optically coupled to the plurality
of light-receiving elements, respectively, characterized in that the
optical module substrate is formed from an insulating ceramic.
When the optical module substrate is formed from an insulating material, no
insulating film need be formed between printed interconnections and the
optical module substrate, and a parasitic capacitance is prevented. In
addition, when the optical module substrate is formed from a ceramic, the
workability and working accuracy are ensured.
The optical module substrate of the present invention is preferably
characterized in that the insulating ceramic is an insulating ceramic
selected from the group consisting of alumina ceramic, zirconia ceramic,
calcium titanate ceramic, silicon nitride ceramic, and aluminum nitride
ceramic.
The optical module substrate of the present invention may be characterized
in that the substrate comprises a reflection surface for reflecting light
emerging from an end face of each of the plurality of optical fibers of
the optical fiber array and making the light incident on a corresponding
one of the light-receiving elements of the light-receiving element array,
and the reflection surface makes an angle of substantially 45.degree. with
respect to a mounting surface for mounting the optical fiber array.
In an optical module substrate made of silicon, it is difficult to form a
reflection surface that makes an angle of 45.degree. with respect to the
mounting surface because of the problem of crystal surface. However, in
the optical module substrate made of a ceramic, the reflection surface
that makes an angle of 45.degree. with respect to the mounting surface can
be easily accurately formed, and the optical coupling efficiency between
the light-receiving element array and the optical fiber array can be
easily improved.
According to the present invention, there is also provided a light-emitting
module characterized by comprising a light-emitting element array formed
by arraying a plurality of light-emitting elements, an optical fiber array
formed by arraying a plurality of optical fibers optically coupled to the
plurality of light-emitting elements, respectively, an optical module
substrate for mounting the light-emitting element array and the optical
fiber array, a driving circuit for driving the light-emitting element
array, and a base for mounting the optical module substrate and the
driving circuit, wherein the optical module substrate comprises the
optical module substrate formed from an insulating ceramic.
When the optical module substrate formed from an insulating ceramic is
used, a parasitic capacitance is prevented, and the workability and
working accuracy of the optical module substrate are ensured.
According to the present invention, there is also provided a
light-receiving module characterized by comprising a light-receiving
element array formed by arraying a plurality of light-receiving elements
to output an electrical signal corresponding to a light-receiving amount
of each of the plurality of light-receiving elements, an optical fiber
array formed by arraying a plurality of optical fibers optically coupled
to the plurality of light-receiving elements, respectively, an optical
module substrate for mounting the light-receiving element array and the
optical fiber array, an amplification circuit for amplifying the
electrical signal output from the light-receiving element array, and a
base for mounting the optical module substrate and the amplification
circuit, wherein the optical module substrate comprises the optical module
substrate formed from an insulating ceramic.
When the optical module substrate formed from an insulating ceramic is
used, a parasitic capacitance is prevented, and the workability and
working accuracy of the optical module substrate are ensured.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing an optical parallel transmission
receiver according to an embodiment of the present invention immediately
after resin molding;
FIG. 2 is a perspective view showing a PD subcarrier 3 usable for the
optical parallel transmission receiver according to an embodiment of the
present invention, which is viewed from an MT ferrule 2 side;
FIG. 3 is a perspective view showing the PD subcarrier 3 usable for the
optical parallel transmission receiver according to an embodiment of the
present invention, which is viewed from the rear side;
FIG. 4 is a perspective view showing a subassembly combining guide pins 1,
MT ferrule 2, and PD subcarrier 3 usable for the optical parallel
transmission receiver according to an embodiment of the present invention,
which is viewed from the MT ferrule 2 side;
FIG. 5 is a perspective view showing the subassembly shown in FIG. 4, which
is upside down and viewed from the PD subcarrier 3 side;
FIG. 6 is a perspective view showing the subassembly shown in FIG. 4, from
which the MT ferrule 2 is detached;
FIG. 7 is a perspective view showing a state before bending connecting lead
pins 3e into an almost S shape while omitting the half of a lid 2c of the
MT ferrule 2 for the illustrative convenience so as to indicate the
connection state between optical fibers and light-receiving elements
usable for the optical parallel transmission receiver according to an
embodiment of the present invention;
FIG. 8 is an exploded perspective view showing the MT ferrule together with
the guide pins usable for the optical parallel transmission receiver
according to an embodiment of the present invention;
FIG. 9 is a perspective view showing a metal lead frame as a constituent
component of the PD subcarrier 3 usable for the optical parallel
transmission receiver according to an embodiment of the present invention;
FIG. 10 is a perspective view showing a state wherein the metal lead frame
usable for the optical parallel transmission receiver according to an
embodiment of the present invention is sandwiched and fixed between a
first flat plate 3b and a second flat plate 3c;
FIG. 11 is a perspective view showing a state wherein the connecting lead
pins 3e shown in FIG. 10 are bent;
FIG. 12 is a perspective view showing, together with the guide pins 1 and
MT ferrule 2, a state wherein a light-receiving element array 3f and
preamplifier IC 3g are mounted on die pad portions 3j1 and 3j2 shown in
FIG. 11, respectively, and connected by wire bonding;
FIG. 13 is a perspective view showing, together with the MT ferrule 2, the
PD subcarrier 3 using back-incident-type light-receiving elements, which
is usable for the optical parallel transmission receiver according to an
embodiment of the present invention;
FIG. 14 is a perspective view showing the PD subcarrier 3 shown in FIG. 13,
which is viewed from the lower side;
FIG. 15 is a perspective view showing the connection state between the
light-receiving element array 3f and the preamplifier IC 3g which are
usable for the optical parallel transmission receiver according to an
embodiment of the present invention;
FIG. 16 is a perspective view showing a connection method according to
another embodiment, which is usable for the optical parallel transmission
receiver according to an embodiment of the present invention;
FIG. 17 is a perspective view showing an optical parallel transmission
transmitter immediately after resin molding, which is usable for an
optical parallel transmission transmitter according to the first
embodiment of the present invention;
FIG. 18 is an exploded perspective view showing the internal structures of
an MT ferrule 12 and LD subcarrier 13 before resin molding, which are
usable for the optical parallel transmission transmitter according to the
first embodiment of the present invention;
FIG. 19 is a perspective view showing a state wherein the lid of the LD
subcarrier 13 usable for the optical parallel transmission transmitter
according to the first embodiment of the present invention is omitted;
FIG. 20 is a perspective view showing the LD subcarrier 13 usable for the
optical parallel transmission transmitter according to the first
embodiment of the present invention together with a lead frame 14 and
ceramic substrate 16 (corresponding to the optical parallel transmission
transmitter shown in FIG. 19 from which the MT ferrule 12 is omitted);
FIG. 21 is an exploded perspective view showing the MT ferrule together
with guide pins usable for the optical parallel transmission transmitter
according to the first embodiment of the present invention;
FIG. 22 is a perspective view showing the guide pins and MT ferrule shown
in FIG. 21, which are viewed from the lower side;
FIG. 23 is a perspective view showing a metal lead frame as a constituent
component of the LD subcarrier 13 usable for the optical parallel
transmission transmitter according to the first embodiment of the present
invention;
FIG. 24 is a perspective view showing a state wherein the metal lead frame
usable for the optical parallel transmission transmitter according to the
first embodiment of the present invention is sandwiched and fixed between
a first flat plate 13b and a second flat plate 13c;
FIG. 25 is a perspective view showing a state wherein the structure shown
in FIG. 24 is viewed from a driver IC array mounting portion 13j1 side;
FIG. 26 is a perspective view showing, together with guide pins 11, a state
wherein a light-emitting element array 13f, driver IC array 13g, and
monitor light-receiving element 13p are mounted on the die pad portions
13j1 and 13j2 and 13m shown in FIG. 24, respectively;
FIG. 27 is a perspective view showing the optical parallel transmission
transmitter according to the first embodiment of the present invention
before resin molding, which is usable for an optical parallel transmission
transmitter according to the second embodiment and is viewed from a
ceramic substrate 26 side while detaching a lid 23e of the LD subcarrier;
FIG. 28 is a perspective view showing a state wherein a lid 22c of an MT
ferrule 22 is also detached from the optical parallel transmission
transmitter shown in FIG. 27;
FIG. 29 is a perspective view showing the state wherein the lid 22c and lid
23e are detached, which is viewed from the MT ferrule 22 side;
FIG. 30 is a perspective view showing an LD subcarrier 23 usable for the
optical parallel transmission transmitter according to the second
embodiment of the present invention together with a lead frame 24 and
ceramic substrate 26;
FIG. 31 is a perspective view showing a state wherein the lid 23e of the LD
subcarrier 23 of the optical parallel transmission transmitter according
to the second embodiment of the present invention shown in FIG. 30 is
removed;
FIG. 32 is a perspective view showing, together with the MT ferrule 22, the
LD subcarrier 23 having no lid 23e, which is usable for the optical
parallel transmission transmitter according to the second embodiment of
the present invention;
FIG. 33 is a perspective view showing, together with guide pins 21, the LD
subcarrier 23 having no lid 23e, which is usable for the optical parallel
transmission transmitter according to the second embodiment of the present
invention;
FIG. 34 is a perspective view showing a first flat plate 23b, second flat
plate 23c, and two lead frames held by them, which are usable for the
optical parallel transmission transmitter according to the second
embodiment of the present invention;
FIG. 35 is a perspective view showing a state wherein a light-emitting
element array 23f, driver IC array 23g, and monitor light-receiving
element 23p are removed from the first flat plate 23b shown in FIG. 34;
FIG. 36 is a perspective view showing a metal lead frame as a constituent
component of the LD subcarrier 23 usable for the optical parallel
transmission transmitter according to the second embodiment of the present
invention;
FIG. 37 is a perspective view showing the LD subcarrier 23 having no lid
23e, together with the guide pins 21 and MT ferrule 22, which are usable
for the optical parallel transmission transmitter according to the second
embodiment of the present invention;
FIG. 38 is a sectional view showing the MT ferrule 22 and LD subcarrier 23,
which are usable for the optical parallel transmission transmitter
according to the second embodiment of the present invention and are taken
along a plane perpendicular to the optical fiber array surface;
FIG. 39 is a perspective view showing the optical parallel transmission
transmitter before resin molding, which is usable for the optical parallel
transmission transmitter according to the second embodiment of the present
invention and is viewed from the ceramic substrate 26 side while omitting
an MT ferrule 32;
FIG. 40 is a perspective view showing a state wherein a lid 33e of the
optical parallel transmission transmitter shown in FIG. 39 is removed;
FIG. 41 is a perspective view showing an LD subcarrier 33 usable for an
optical parallel transmission transmitter according to the third
embodiment of the present invention;
FIG. 42 is a perspective view showing the LD subcarrier 33 usable for the
optical parallel transmission transmitter according to the third
embodiment of the present invention.
FIG. 43 is a perspective view showing the LD subcarrier 33 usable for the
optical parallel transmission transmitter according to the third
embodiment of the present invention;
FIG. 44 is a perspective view showing the LD subcarrier 33 usable for the
optical parallel transmission transmitter according to the third
embodiment of the present invention;
FIG. 45 is a perspective view showing the lid 33e of the LD subcarrier 33
usable for the optical parallel transmission transmitter according to the
third embodiment of the present invention;
FIG. 46 is a perspective view showing the lid 33e of the LD subcarrier 33
usable for the optical parallel transmission transmitter according to the
third embodiment of the present invention;
FIG. 47 is a perspective view showing the lid 33e of the LD subcarrier 33
usable for the optical parallel transmission transmitter according to the
third embodiment of the present invention;
FIG. 48 is a perspective view showing the lid 33e of the LD subcarrier 33
usable for the optical parallel transmission transmitter according to the
third embodiment of the present invention;
FIG. 49 is a perspective view showing the lid 33e of the LD subcarrier 33
usable for the optical parallel transmission transmitter according to the
third embodiment of the present invention;
FIG. 50 is an exploded perspective view of a light-emitting module;
FIG. 51 is a perspective view of the light-emitting module;
FIG. 52 is a perspective view of a base;
FIG. 53 is a perspective view of an optical fiber array;
FIG. 54 is a perspective view of the optical fiber array;
FIG. 55 is a perspective view of a semiconductor laser array;
FIG. 56 is a perspective view of a platform;
FIG. 57 is a perspective view of a wiring board;
FIG. 58 is a perspective view of a platform;
FIG. 59 is a perspective view of a platform; and
FIG. 60 is a view showing a state wherein an optical fiber array and
photodiode array are mounted on the platform.
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with
reference to the accompanying drawings. The same reference numerals denote
the same elements throughout the drawings, and a detailed description
thereof will be omitted.
FIG. 1 is a perspective view showing an optical parallel transmission
receiver according to an embodiment of the present invention immediately
after resin molding. For the optical parallel transmission receiver
according to this embodiment, a pair of guide pins 1, an MT ferrule 2 for
holding multiple optical fibers, and a PD subcarrier 3 for holding
light-receiving elements are resin-molded together with a lead frame 4,
thereby constructing a mold package 5.
After that, leads extending from the sides and rear side of the mold
package 5 are cut in front of support leads, and tie bars between the
leads are cut.
In this embodiment, the mold package 5 is used to fix the elements.
However, a metal package or plastic package may be used to fix the
elements.
FIGS. 2 and 3 are perspective views showing the optical parallel
transmission receiver according to this embodiment before resin molding.
FIG. 2 is a perspective view showing the PD subcarrier 3 viewed from the
MT ferrule 2 side. FIG. 3 is a perspective view showing the PD subcarrier
3 viewed from the rear side. FIGS. 2 and 3 are schematic views aiming at
clarity. For example, only some wires for connecting the PD subcarrier 3
and a ceramic substrate 6 are illustrated.
The guide pins 1 and lead frame 4 are held by a mold for resin molding
whereby the relative position between the guide pins 1, MT ferrule 2, PD
subcarrier 3, lead frame 4, and ceramic substrate 6, which are fixed by
the mold package 5, is accurately realized. At this stage, the guide pins
1, MT ferrule 2, and PD subcarrier 3 are accurately assembled with
reference to the guide pins 1.
The guide pins 1 are normally formed from a metal and have a length longer
than at least the total length of the MT ferrule 2 and PD subcarrier 3
combined with each other. Another MT ferrule (not shown) is inserted on
the guide pins 1 projecting from the MT ferrule 2. To facilitate
insertion, the distal ends of the guide pins 1 are tapered. The guide pins
1 inserted into the MT ferrule 2 are not fixed. However, to prevent the
other MT ferrule from removing the guide pins 1 when the other MT ferrule
is detached, the guide pins 1 are held in the MT ferrule 2 by a certain
force. A plurality of V-grooves are formed between the guide pins 1 at a
predetermined interval in parallel to the longitudinal direction of the
guide pins 1. A plurality of optical fibers are fixed in the grooves.
Hence, the plurality of optical fibers are arrayed at a predetermined
pitch that normally matches the standard of the other MT ferrule.
The MT ferrule 2 has at least a function of holding a plurality of optical
fibers and guide pins. For this purpose, the MT ferrule 2 has fiber
holding portions corresponding to the number of optical fibers to be held
and pin holding portions corresponding to the number of guide pins to be
held. The detailed structure will be described later with reference to
FIG. 8.
The PD subcarrier 3 is constructed by two, first flat plate 3b and second
flat plate 3c forming a pair of through holes 3a and formed from a
plastic, and a metal lead frame having, at some portions, heat dissipation
lead pins 3d and connecting lead pins 3e and sandwiched between the first
flat plate 3b and the second flat plate 3c, and is attached between the MT
ferrule 2 and the ceramic substrate 6 with reference to the guide pins 1.
To accurately position the PD subcarrier 3 with respect to the MT ferrule
2, the through holes 3a each for receiving one end of a corresponding one
of the guide pins 1 are formed in the PD subcarrier 3 to extend from the
surface of the PD subcarrier 3, which opposes the MT ferrule 2, to the
opposite surface (FIG. 3). A light-receiving element array 3f and
preamplifier IC 3g are accurately mounted on the PD subcarrier 3 with
reference to the through holes 3a. For this reason, the plurality of
optical fibers attached to the MT ferrule 2 and the plurality of
light-receiving element arrays 3f mounted on the PD subcarrier 3 can be
easily accurately optically coupled only by inserting the PD subcarrier 3
on the guide pins 1. The heat dissipation lead pins 3d extending from both
sides of the PD subcarrier 3 effectively dissipate heat from the
preamplifier, which is transmitted through the metal lead frame. Grounding
is also possible using the heat dissipation lead pins 3d. After the PD
subcarrier 3 is packaged, the connecting lead pins 3e are bent into an
almost S shape (FIG. 3) and easily connected to the ceramic substrate 6 by
wire bonding. In this embodiment, the PD subcarrier 3 and ceramic
substrate 6 are connected by wires. However, the connecting lead pins 3e
and electrode terminals on the ceramic substrate 6 may be directly
connected.
The lead frame 4 comprises a support lead 4a which forms a rectangular
frame, a die pad 4b on which the ceramic substrate 6 is mounted, and lead
pins 4c for connecting the die pad 4b and support lead 4a.
The ceramic substrate 6 is mounted on the die pad 4b of the lead frame 4.
The ceramic substrate 6 need not be strictly positioned as far as it is
connected to the PD subcarrier 3 by wires. Electronic circuits (signal
processing circuit, waveform shaping circuit, amplification circuit, and
the like) necessary for driving the light-receiving elements are formed on
the upper surface of the ceramic substrate 6.
FIG. 4 is a perspective view showing a subassembly combining the guide pins
1, MT ferrule 2, and PD subcarrier 3 usable in this embodiment, which is
viewed from the MT ferrule 2 side. FIG. 5 is a perspective view showing
the subassembly shown in FIG. 4, which is turned over and viewed from the
PD subcarrier 3 side. FIG. 6 is a perspective view showing the subassembly
shown in FIG. 4, from which the MT ferrule 2 is removed. FIG. 7 is a
perspective view showing a state before bending the connecting lead pins
3e into an almost S shape while omitting the half of a lid 2c of the MT
ferrule 2 for the illustrative convenience so as to indicate the
connection state between the optical fibers and the light-receiving
elements. To clearly indicate details, wires for connecting the connecting
lead pins 3e and preamplifier 3f and wires for connecting the
light-receiving element array 3f and preamplifier IC 3g are not
illustrated.
As an important point, the plurality of optical fibers (e.g., a fiber
array) and the plurality of light-receiving elements (e.g., a
light-receiving element array) are accurately positioned using the guide
pins as a mechanical reference such that the optical fibers and the
light-receiving surfaces of the light-receiving elements are perpendicular
(optically coupled) to each other. It is difficult to accurately position
optical fibers and light-receiving elements held by separate members on
the .mu.m order. However, accurate positioning is realized through the
guide pins by accurately forming holes for fixing the guide pins in the
two members.
The guide pins 1, MT ferrule 2, and PD subcarrier 3, which construct this
subassembly, will be sequentially described on the basis of FIGS. 4 to 7
with reference to FIGS. 8 to 11.
The guide pins 1 are normally formed into a long columnar shape to obtain
the function of positioning a plurality of members (MT ferrule 2 and PD
subcarrier 3 in this embodiment) to which the guide pins 1 are inserted
(FIGS. 7 and 8). As for the material, the guide pins 1 are formed from a
material that does not deform and curve under the use environment of the
receiver, e.g., stainless steel. The projecting amount of the guide pins 1
from the MT ferrule 2 is calculated in consideration of connection and
optical axis alignment to the MT connector or MT ferrule on the partner
side, which is inserted to the guide pins 1. The length of each guide pin
1 is determined on the basis of the calculated value.
The MT ferrule 2 comprises the lid 2c and a fiber holding member 2d (FIGS.
6 and 8). The two plate members, i.e., the lid 2c and fiber holding member
2d are abutted against each other. The pair of guide pins 1 and the
plurality of optical fibers are held between the abutment surfaces. For
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