U.S. patent application number 09/725892 was filed with the patent office on 2001-04-19 for optical system unit for optical transceiver.
Invention is credited to Kawai, Motoyoshi.
Application Number | 20010000316 09/725892 |
Document ID | / |
Family ID | 18349482 |
Filed Date | 2001-04-19 |
United States Patent
Application |
20010000316 |
Kind Code |
A1 |
Kawai, Motoyoshi |
April 19, 2001 |
Optical system unit for optical transceiver
Abstract
An optical system unit for optical transceiver is fabricated
integral with lenses by molding of a resin material for providing a
desired level of the optical characteristics with no use of
mirrors. The optical system unit for optical transceiver 201 for
optically coupling with a connector 202 having a fiber optic cable
205 has a pair of convex lenses 212 and 213 thereof provided to
face the coupling end of a transmission optical fiber 203 and the
coupling end of a reception optical fiber 204 respectively. The two
lenses 212 and 213 may be identical in the optical characteristics.
A lead frame 215 having two steps is provided beneath the two
lenses 212 and 213. A light emitting device 216 and a light
receiving device 217 are mounted on the two, upper and lower, steps
of the lead frame 215 respectively. The lead frame 215 is carefully
bent at a certain angle, aligned with the axes of the optical
fibers, and embedded in the resin material. In the molding of the
resin material, the two convex lenses 212 and 213 are formed
integrally. The optical system unit 201 employing no mirrors can
hardly be susceptible to a change in the ambient temperature.
Inventors: |
Kawai, Motoyoshi; (Tokyo,
JP) |
Correspondence
Address: |
MCGINN & GIBB, PLLC
8321 OLD COURTHOUSE ROAD
SUITE 200
VIENNA
VA
22182-3817
US
|
Family ID: |
18349482 |
Appl. No.: |
09/725892 |
Filed: |
November 30, 2000 |
Current U.S.
Class: |
385/33 ;
385/93 |
Current CPC
Class: |
G02B 6/4246 20130101;
H01L 2924/181 20130101; G02B 6/4266 20130101; G02B 6/4277 20130101;
H01L 2224/48137 20130101; G02B 6/4201 20130101; H01L 2224/48247
20130101; G02B 6/4206 20130101; G02B 6/4292 20130101; H01L
2224/48091 20130101; H01L 2224/48091 20130101; H01L 2924/181
20130101; H01L 2924/3025 20130101; H01L 2924/3025 20130101; G02B
6/4249 20130101; H01L 2924/00012 20130101; H01L 2924/00 20130101;
H01L 2924/00014 20130101 |
Class at
Publication: |
385/33 ; 359;
385/93 |
International
Class: |
G02B 006/32; G02B
006/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 12, 1999 |
JP |
11-341882 |
Claims
What is claimed is:
1. An optical system unit for optical transceiver comprising: a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; a lead frame
provided in the optically transparent resin material and formed by
bending to have two steps so that the distances of the two steps
along the axes of the optical fibers from the one end of the
transmission optical fiber and the one end of the reception optical
fiber respectively are different; a light emitting device provided
in the optically transparent resin material as located on one step
of the lead frame to face the one end the transmission optical
fiber; and a light receiving device provided in the optically
transparent resin material as located on the other step of the lead
frame to face the one end the reception optical fiber.
2. An optical system unit for optical transceiver according to
claim 1, wherein the lead frame has rows of perforations provided
therein along the bending lines so that the distances of the steps
can be adjusted by varying the angle of bending.
3. An optical system unit for optical transceiver comprising: a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; a first lead frame
and a second lead frame provided in the optically transparent resin
material and located so that their distances along the axes of the
optical fibers from the one end of the transmission optical fiber
and the one end of the reception optical fiber respectively are
different; a light emitting device provided on the first lead frame
to face the one end the transmission optical fiber; and a light
receiving device provided on the second lead frame to face the one
end the reception optical fiber.
4. An optical system unit for optical transceiver according to
claim 3, wherein one of the first and second lead frames which is
nearer to the one end of the optical fiber has a window-like
opening provided therein for clearing the optical path to the light
transmitting or receiving device mounted on the other lead
frame.
5. An optical system unit for optical transceiver according to
claim 4, wherein the other lead frame also has a window-like
opening provided therein at the same position as of the opening of
the nearer lead frame and a light receiving device of back-side
reception type is mounted to the side opposite to the optical fiber
facing side of the other lead frame with its light receiving
surface oriented to face the one end of the optical finer across
the two openings.
6. An optical system unit for optical transceiver according to
claim 3, wherein a shielding sheet made of a conductive material is
provided between the first lead frame and the second lead frame for
inhibiting the light receiving device from receiving unwanted
components of the light emitted from the light emitting device and
connected to the ground for eliminating electrical noises.
7. An optical system unit for optical transceiver comprising: a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; a lead frame
provided in the optically transparent resin material, arranged in
parallel with a plane on which the axes of the transmission optical
fiber and the reception optical fiber extend, and formed to such a
shape that the distances of two portions of its upper edge from the
one end of the transmission optical fiber and the one end of the
reception optical fiber respectively are different; a light
emitting device provided on one portion of the upper edge of the
lead frame with its light emitting surface oriented to face the one
end the transmission optical fiber; and a light receiving device
provided on the other portion of the upper edge of the lead frame
with its light receiving surface oriented to face the one end the
reception optical fiber.
8. An optical system unit for optical transceiver according to any
of claims 1, 3, and 7, wherein the transmission lens, the reception
lens, and the relevant components are provided two or more sets
corresponding to a number of the fiber optic cables employed.
Description
FIELD OF THE INVENTION
1. The present invention relates to an optical system unit for
optical transceiver and particularly an optical system unit for
optical transceiver arranged of receptacle type for coupling with a
plurality of optical fibers and transmitting and receiving optical
signal over the optical fibers.
BACKGROUND OF THE INVENTION
2. It is contemplated that an optical system unit for optical
transceiver for coupling with a plurality of optical fibers and
transmitting and receiving optical signals over the optical fibers
is equivalent to a connection hub (a cable coupler) for coupling a
group of LAN (local area network) cables for a local network such
as in an office.
3. Any LAN cable for transmission of electric signals can be joined
at one end to a relatively smaller connector and also can transmit
and receive a signal over a single line. Accordingly, the hub for
coupling the LAN cables for electric signals is common available of
a compact size.
4. On the contrary, a conventional optical system unit for optical
transceiver is designed having a desired number of connectors, each
connector joined with a fiber optic cable accommodating a
transmission optical fiber and a fiber optic cable accommodating a
reception optical fiber.
5. FIG. 9 schematically illustrates a primary part of such a
conventional optical system unit for optical transceiver. The
conventional optical system unit for optical transceiver 101 may be
coupled with two or more connectors 102. The connector 102 is
joined with one end of a transmission fiber optic cable 103 and one
end of a reception fiber optic cable 104. The optical system unit
for optical transceiver 101 includes a transmission lens 107
located opposite to and spaced by a certain distance from the end
of a transmission optical fiber 106 accommodated in the
transmission fiber optic cable 103 of the connector 102. Similarly,
it includes a reception lens 109 located opposite to and spaced by
a certain distance from the end of a reception optical fiber 108
accommodated in the reception fiber optic cable 104. Provided on
the other side of the lenses 107 and 109 opposite to the connector
102 side is a lead frame 111. A light emitting diode 112 and a
photo diode 113 are mounted on the lead frame 111 to face the
transmission lens 107 and the reception lens 109 respectively.
6. In FIG. 9, the connector 102 is illustrated as a single unit. It
is understood that the optical system unit 101 for optical
transceiver when coupled with two or more of the connectors 102
includes a corresponding number of such optical systems.
7. As the connector 102 is joined with the two fiber optic cables
103 and 104, the conventional optical system unit for optical
transceiver 101 is relatively large in the overall size. This
allows the transmission lens 107 and the reception lens 109 to be
used of large size. Also, this permits the light emitting diode 112
and the photo diode 113 to be generously spaced from each other,
thus improving the separation between a transmission signal and a
received signal.
8. However, as its connector 102 is large, the conventional optical
system unit for optical transceiver 101 becomes bulky in the
dimensions. As compared with the LAN cable joined hub as a like
unit for transmission and reception of electric signals, the
conventional optical system unit for optical transceiver 101 maybe
too large. It is hence proposed to provide a modified optical
system unit for optical transceiver which can be coupled with a
smaller connector accompanied with a single fiber optic cable for
transmission and reception of optical signals.
9. FIG. 10 is an enlarged view showing schematically a modified
optical system unit for optical transceiver coupled with one end of
the fiber optic cable. The fiber optic cable 121 includes a
transmission optical fiber 122 and a reception optical fiber 123
joined closely to each other by a distance L. The distance L maybe
as short as 0.75 mm. As a result, a connector 124 joined with the
fiber optic cable 121 can be decreased to a size equal to that of
the common LAN cable connector for electric signals. Consequently,
the modified optical system unit for optical transceiver 125
coupled with the connector 124 will be minimized in the size.
10. However, when the distance L between the two optical fibers 122
and 123 is very small, their corresponding lenses 126 and 127, the
light emitting diode 128, and the photo diode 129 may hardly be
aligned with the two optical fibers 122 and 123. For compensation,
a group of mirrors 131 to 134 are utilized to separate the two
optical paths 135 and 136, denoted by the one-dot chain lines, from
each other in directions orthogonal to the axes of the optical
fibers 122 and 123 as shown in FIG. 10 such a technique is
disclosed in "Opto-com", pp. 60, April 1998.
11. As the modified optical system unit for optical transceiver 125
shown in FIG. 10 includes the mirrors 131 to 134 for transmitting
and receiving a pair of optical signals, its price will unfavorably
be increased. Accordingly, some attempts for forming the lenses and
the mirrors integrally by molding of an optically transparent
material have been proposed. One of the attempts is depicted in the
Electric Components & Technology Conference 1998 proceeding,
"Low Wave Length Transparent Epoxy Mold Optical Data Link" by
Ichiro Tonai et al.
12. FIG. 11 is a view of the connector coupling end of such a
modified optical system unit for optical transceiver described in
the above proceeding, seen from the connector side. FIG. 12 is a
cross sectional view of the modified optical system unit for
optical transceiver 101 taken along the line A-A of FIG. 11
vertical to the sheet of paper. As shown in FIG. 12, the optical
system unit for optical transceiver 141 is coupled with a connector
142.
13. The connector 142 shown in FIG. 12 is joined with a two-core
fiber optic cable 145 having a transmission optical fiber 143 and a
reception optical fiber 144. The connector 142 has two M type
ferrule positioning holes 146 and 147 provided in the front side
thereof. When its M type ferrule positioning holes 146 and 147 are
in engagement with a pair of corresponding M type ferrule
positioning pins 148 and 149 mounted at the opposite positions on
the front side of the optical system unit for optical transceiver
141, the connector 142 is correctly coupled with the optical system
unit for optical transceiver 141.
14. The optical system unit for optical transceiver 141
incorporates a resin body 151 in which the two M type ferrule
positioning pins 148 and 149 are implanted. In the resin body 151,
each of the opposite position of the transmission optical fiber 143
and the reception optical fiber 144 project hemispherically, and
the resin body 151 construct the convex lens 152 and 153,
respectively. The resin body 151 is made of a transparent resin
material which is transparent for both a mode of light transmitted
to the transmission optical fiber 143 and a mode of light received
from the reception optical fiber 144. Also, a lead frame 155 of a
sheet form is embedded in the resin material 151 to extend on a
plane orthogonal to the M type ferrule positioning pins 148 and
149, A light emitting device 156 for emitting light via the lens
152 to the transmission optical fiber 143 is mounted on the lead
frame 155 to face the transmission optical fiber 143. Also, a light
receiving device 157 for receiving light transmitted via the lens
153 from reception optical fiber 144 is mounted on the lead frame
155 to face the reception optical fiber 144. The light emitting
device 156 is connected by a wire 161 to a transmission signal line
158 which is provided flush with the lead frame 155. Similarly, the
light receiving device 157 is connected by a wire 162 to a
reception signal line 159 which is provided flush with the leaf
frame 155.
15. In the optical system unit for optical transceiver 141 having
the above arrangement, both the light emitting device 156 and the
light receiving device 157 are mounted on the single lead frame.
Accordingly, the distance from the light emitting device 156 to the
end of the fiber optic cable 145 is equal to that from the light
receiving device 157. In practice, the light emitting device 156
and the light receiving device 157 may commonly be different from
each other in the optical characteristics including the size of the
light transmitting, or receiving area- For compensation, the two
convex lenses 152 and 153 are separately designed and fabricated
for giving optimum effects to different focal length or
aberration.
16. The modified optical system unit for optical transceiver 141
shown in FIGS. 11 and 12 allows the light emitting device 156 and
the light receiving device 157 to be aligned with the transmission
optical fiber 122 and the reception optical fiber 123 respectively,
thus eliminating the mirrors which are essentially provided in the
previous optical system unit for optical transceiver 125 shown in
FIG. 10. Also, as its lenses are fabricated by molding of a resin
material, the optical system unit for optical transceiver 141 will
be improved in the cost down.
17. However, the optical system unit for optical transceiver 141
shown in FIGS. 11 and 12 has the transmission optical fiber 122 and
the reception optical fiber 123 spaced from each other by the
distance L which is as short as 0.75 mm similar to that shown in
FIG. 10. Accordingly, because the two convex lenses 152 and 153
formed integral with the resin body 141 by the molding process are
very small in the size, their dimensional accuracy enough to have
desired lengths of the focal distance may hardly be feasible.
18. The reduction of the number of components by molding the resin
material may be achieved with the system unit shown in FIG. 10.
More particularly, while the two lenses 129 and 127 are formed as a
pair of arcuate projections as shown in FIGS. 11 and 12, the
mirrors 131 to 134 are implemented by facets exposed to the air. As
a result, those optical components are formed in a single unit.
Accordingly, the lenses will no more be fabricated separately and
the optical system unit for optical transceiver will be reduced in
the production cost. It is however true that the resin material
expands or contracts as the temperature changes. In case that the
mirrors are formed on facets tilted at a certain angle, any change
in the ambient temperature ranging from -40 to +85.degree.C. may
generate angular variation or distortion on the tilted facets.
Consequently, the optical system unit for optical transceiver 125
shown in FIG. 10 can be formed by molding the resin material but
with an unfavorable level of the optical characteristics.
SUMMARY OF THE INVENTION
19. It is thus an object of the present invention to provide an
optical system unit for optical transceiver which is so formed
integral with lenses by molding of a resin material as to exhibit a
favorable level of the optical characteristics with no use of
mirrors.
20. According to claim 1 of the present invention, an optical
system unit for optical transceiver is provided comprising: (a) a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; (b) a lead frame
provided in the optically transparent resin material and formed by
bending to have two steps so that the distances of the two steps
along the axes of the optical fibers from the one end of the
transmission optical fiber and the one end of the reception optical
fiber respectively are different, (c) a light emitting device
provided in the optically transparent resin material as located on
one step of the lead frame to face the one end the transmission
optical fiber; and (d) a light receiving device provided in the
optically transparent resin material as located on the other step
of the lead frame to face the one end the reception optical
fiber.
21. As defined in claim 1, the transmission lens and the reception
lens are formed integrally by a resin material which is transparent
for the applied wavelengths of light so as to face the transmission
optical fiber and the reception optical fiber respectively of a
fiber optic cable and the distance between the light emitting
device and the light receiving device is determined on the basis of
the optical characteristic of the two lenses. Accordingly, the
optical system becomes simpler in the arrangement with no use of
mirrors. In addition, the transmission lens and the reception lens
can commonly be used as are identical in the optical
characteristics and the data of conventional similar lenses can be
utilized for designing. This will facilitate the designing process
of the system unit hence contributing to the speed-up and the cost
down of the development and manufacturing. Moreover, as no mirrors
are used, the system unit will remain stable regardless of changes
in the ambient temperature. The single lead frame is bent to such a
shape that the bent can successfully shield unwanted components of
the light emitted from the light emitting device. Also, the
difference in the distance to the lens between the light emitting
device and the light receiving device can easily be controlled by
varying the angle of bending the lead frame.
22. According to claim 2 of the present invention, the optical
system unit for optical transceiver defined in claim 1 is modified
in which the lead frame has rows of perforations provided therein
along the bending lines so that the distances of the steps can be
adjusted by varying the angle of bending.
23. As defined in claim 2, the lead frame according to claim has
the rows of perforations provided therein along the bending lines.
Accordingly, the light emitting device and the light receiving
device mounted on the lead frame are free from excessive stress
developed during the bending process and can thus be prevented from
unwanted physical damage.
24. According to claim 3 of the present invention, an optical
system unit for optical transceiver is provided comprising. (a) a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; (b) a first lead
frame and a second lead frame provided in the optically transparent
resin material and located so that their distances along the axes
of the optical fibers from the one end of the transmission optical
fiber and the one end of the reception optical fiber respectively
are different; (c) a light emitting device provided on the first
lead frame to face the one end the transmission optical fiber; and
(d) a light receiving device provided on the second lead frame to
face the one end the reception optical fiber.
25. As defined in claim 3, the transmission lens and the reception
lens are formed by the transparent resin material, which is
transparent for wavelengths of light to be used, so as to face the
end of the transmission optical fiber and the end of the reception
optical fiber respectively of the fiber optic cable. The two, first
and second, lead frames are embedded in the resin material so that
the distance between the light emitting device and the light
receiving device can be determined arbitrarily and separately
depending on the optical characteristics of the two resin lenses.
Accordingly, the optical system can be simple in the arrangement
with no use of mirrors for reflecting the light. In addition, the
transmission lens and the reception lens can commonly be used as
are identical in the optical characteristics and the data of
conventional similar lenses can be utilized for designing. This
will facilitate the designing process of the system unit hence
contributing to the speed-up and the cost down of the development
and manufacturing, Moreover, as no mirrors are used, the system
unit will remain stable regardless of changes in the ambient
temperature.
26. According to claim 4 of the present invention, the optical
system unit for optical transceiver defined in claim 3 is modified
in which one of the first and second lead frames which is nearer to
the one end of the optical fiber has a window-like opening provided
therein for clearing the optical path to the light transmitting or
receiving device mounted on the other lead frame.
27. As a result, the two lead frames can be placed one over the
other. This will implement the spatial arrangement of the two lead
frames readily and accurately in the molding process of the resin
material.
28. According to claim 5 of the present invention, the optical
system unit for optical transceiver defined in claim 4 is modified
in which the other lead frame also has a window-like opening
provided therein at the same position as of the opening of the
nearer lead frame and a light receiving device of back-side
reception type is mounted to the side opposite to the optical fiber
facing side of the other lead frame with its light receiving
surface oriented to face the one end of the optical finer across
the two openings.
29. As defined in claim 5, the light receiving device of back-side
reception type can be used having relevant terminals mounted on the
side opposite to the light receiving side. The difference between
the distance of the light emitting device to its corresponding lens
and the distance of the light receiving device to its corresponding
lens can be adjusted by controlling the thickness of the two lead
frames.
30. According to claim 6 of the present invention, the optical
system unit for optical transceiver defined in claim 3 is modified
in which a shielding sheet made of a conductive material is
provided between the first lead frame and the second lead frame for
inhibiting the light receiving device from receiving unwanted
components of the light emitted from the light emitting device and
connected to the ground for eliminating electrical noises.
31. The shielding sheet is provided between the two, first and
second, lead frames and connected to the ground for eliminating
electrical and optical noises. Alternatively, besides the shielding
sheet, one of the first and second lead frames may be bent at its
end to protect the light receiving device from receiving unwanted
components of the light from the light emitting device.
32. According to claim 7 of the present invention, an optical
system unit for optical transceiver is provided comprising: (a) a
transmission lens and a reception lens formed of an optically
transparent resin material to project at the distal end of an
arcuate contour towards and locate in front of one end of a
transmission optical fiber and one end of a reception optical fiber
respectively which are spaced by a certain distance from each other
and accommodated in a single fiber optic cable; (b) a lead frame
provided in the optically transparent resin material, arranged in
parallel with a plane on which the axes of the transmission optical
fiber and the reception optical fiber extend, and formed to such a
shape that the distances of two portions of its upper edge from the
one end of the transmission optical fiber and the one end of the
reception optical fiber respectively are different; (c) a light
emitting device provided on one portion of the upper edge of the
lead frame with its light emitting surface oriented to face the one
end the transmission optical fiber; and (d) a light receiving
device provided on the other portion of the upper edge of the lead
frame with its light receiving surface oriented to face the one end
the reception optical fiber.
33. As defined in claim 7, the lead frame is arranged at a right
angle to the orientation of the previous lead frames. Since one end
of the lead frame becomes opposite to the end of the transmission
optical fiber and the end of the reception optical fiber, the light
emitting device and the light receiving device mounted on the lead
frame are used of side emission type and of side reception type
respectively. Accordingly, the light emitting surface and the light
receiving surface of the devices can be set to face the
transmission optical fiber and the reception optical fiber
respectively.
34. According to claim a of the present invention, the optical
system unit for optical transceiver defined in any of claims 1, 3,
and 7 is modified in which the transmission lens, the reception
lens, and the relevant components are provided two or more sets
corresponding to a number of the fiber optic cables employed.
35. The optical system unit for optical transceiver is not only one
applicable to a single fiber optic cable but also capable of
coupling with two or more fiber optic cables. According to the
present invention, the light emitting device and the light
receiving device are favorably aligned with the optical fibers of
each fiber optic cable without using the conventional optical
system where the optical paths are distanced from each other as
shown in FIG. 10. Therefore, the optical system unit for optical
transceiver can be minimized in the overall arrangement.
BRIEF DESCRIPTION OF THE DRAWINGS
36. FIG. 1 is a plan view of a connector coupling side of an
optical system unit for optical transceiver according to the first
embodiment of the present invention, seen from the connector
side;
37. FIG. 2 is a cross sectional view of the optical system unit for
optical transceiver taken along the line B-B of FIG. 1 vertical to
the sheet of paper;
38. FIG. 3 is a plan view of a lead frame of the embodiment with a
transmission signal line and a reception signal line before being
bent;
39. FIG. 4 is a cross sectional view of an optical system unit for
optical transceiver according to the second embodiment with the
coupling end of a fiber optic cable positioned opposite;
40. FIG. 5 is a cross sectional view of an optical system unit for
optical transceiver according to the third embodiment with the
coupling end of a fiber optic cable positioned opposite;
41. FIG. 6 is a cross sectional view of an optical system unit for
optical transceiver according to the fourth embodiment with the
coupling end of a fiber optic cable positioned opposite;
42. FIG. 7 is a cross sectional view of an optical system unit for
optical transceiver according to the fifth embodiment with the
coupling end of a fiber optic cable positioned opposite;
43. FIG. 8 is a cross sectional view of an optical system unit for
optical transceiver according to the sixth embodiment with the
coupling end of a fiber optic cable positioned opposite;
44. FIG. 9 is a schematic view showing a primary part of a
conventional optical system unit for optical transceiver coupled
with two fiber optic cables for transmission and reception of
optical signals respectively;
45. FIG. 10 is a schematic view showing a primary part of a
conventional optical system unit for optical transceiver coupled
with a two-core fiber optic cable and arranged in which two optical
paths for transmission and reception are widely separated from each
other;
46. FIG. 11 is a plan view of a conventional optical system unit
for optical transceiver coupled with a two-core fiber optic cable
and arranged in which two optical paths for transmission and
reception are not widely separated from each other; and
47. FIG. 12 is a cross sectional view of the conventional optical
system unit for optical transceiver taken along the line A-A of
FIG. 11 vertical to the sheet of paper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
48. Some embodiments of the present invention will be described in
more detail.
First Embodiment
49. FIG. 1 is an opened-up view of a connector coupling side of an
optical system unit for optical transceiver, seen from the
connector side, illustrating the first embodiment of the present
invention. FIG. 2 is a cross sectional view of the optical system
unit for optical transceiver taken along the line B-B of FIG. 1
vertically of the sheet of paper. As shown in FIG. 2, the optical
system unit for optical transceiver 201 is coupled with a connector
202 (an MT ferrule).
50. The connector 202 shown in FIG. 2 includes a two-core fiber
optic cable 205 which comprises a transmission optical fiber 203
and a reception optical fiber 204. The connector 202 has a couple
of M type ferrule positioning holes 206 and 207 provided in the
coupling side thereof. With its M type ferrule positioning holes
206 and 207 engaged with two M type ferrule positioning pins 208
and 209 mounted on the coupling side of the optical system unit for
optical transceiver 201, the connector 202 can be coupled with the
optical system unit for optical transceiver 201 at the correct
positional relationship. The connector 202 may commercially be
available as an MT ferrule or a two-core array terminal
standardized by IEC (the International Electro-technical
Commission) 874-16. More particularly, the connector 202 is joined
with the fiber optic cable 205 and then polished at the coupling
side.
51. The two M type ferrule positioning pins 208 and 209 are
implanted in a resin body 211 of the optical system unit for
optical transceiver 201. While the single resin body 211 only is
illustrated, two or more of the resin bodies 211 may be provided in
the optical system unit 201 for coupling with a corresponding
number of the connectors 202, as described previously with FIG.
9.
52. The resin body 211 has two semicircular projections thereof
located opposite to the transmission optical fiber 203 and the
reception optical fiber 204 respectively as shaped to serve as two
convex lenses 212 and 213. The two convex lenses 212 and 213 are
identical to each other in the optical characteristics, dissimilar
to those shown in FIGS. 11 and 12. The resin body 211 is made of a
transparent resin material which can transmit two discrete, input
and output, modes of light received from the reception optical
fiber 204 and transmitting to the transmission optical fiber 203.
The resin material employed in this embodiment may be selected from
a group of materials which are transparent or can transmit the two
modes of light used for the transmission and the reception of
signals even if they are opaque or semi-opaque at the visible
light. More specifically, because the two modes of light used in
this embodiment are 0.85 ?m and 1.31 ?m in wavelength, the resin
material is preferably one which can transmit those wavelengths of
light or provide minimum loss of the light having the wavelengths.
The resin material is not limited to being transparent at the
visible light but may have a black color at extreme.
53. The resin body 211 has a lead frame 215 embedded therein. The
lead frame 215 is bent to have a slope at the center and two, upper
and lower, step portions 215A and 2158 at both the ends thereof
extending in parallel with a plane perpendicular to the M type
ferrule positioning pins 208 and 209. A light emitting device 216
for emitting light via the lens 212 to the transmission optical
fiber 203 is mounted on the upper step portion 215A to face the
transmission optical fiber 203. Also, a light receiving device 217
for receiving light via the lens 213 from the reception optical
fiber 204 is mounted on the lower step portion 215B to face the
reception optical fiber 204. The light emitting device 216 is
connected by a wire 221 to a transmission signal line 219 provided
flush with the upper step portion 215A of the lead frame.
Similarly, the light receiving device 217 is connected by a wire
222 to a transmission signal line 220 provided flush with the lower
step portion 215B of the lead frame.
54. The light emitting device 216 is of a surface-emission type and
may typically be an LED (light emitting diode) or VCSEL (vertical
cavity surface emitting laser). The light receiving element 222 may
be a surface-reception type PD (photo-diode) based on Si (silicon)
or InGaAs (indium-gallium-arsenide).
55. FIG. 3 illustrates the lead frame 215 before bent to a shape,
accompanied with the transmission signal line and the reception
signal line. The lead frame 215 is cut out from a metal sheet.
Then, the light emitting device 216 and the light receiving device
217 are mounted on the lead frame 215 and connected by the wires
221 and 222 to the transmission signal line 219 and the reception
signal line 220 respectively. The lead frame 215 has two lines of
perforations 231 and 232 provided in substantially the center
thereof as spaced from each other by a certain distance. When the
lead frame 215 is bent along the two perforation lines 231 and 232,
its developing stress at the bents can be lessened. This prevents
the light emitting device 216 and the light receiving device 217
mounted on their respective upper and lower step portions 215A and
215B of the lead frame 215 from receiving any undesired stress,
hence eliminating critical faults such as physical fractures. Also,
this permits the upper step portion 215A and the lower step portion
215B to be held linear and thus in parallel with each other.
56. The setting of the optical system unit for optical transceiver
201 having the above arrangement is now explained. As described,
the distance L between the transmission optical fiber 203 and the
reception optical fiber 204 is as short as 0.75 mm in the optical
system unit for optical transceiver 201 of this embodiment. This
allows the two convex lenses 212 and 213 to have the same shape
hence simplifying the design of the arrangement. The two convex
lenses 212 and 213 are made of the resin material and their optical
characteristics including a focal distance may be unsteady in the
accuracy. However, when the two convex lenses 212 and 213 are
formed with the use of a single set of molds which are carefully
designed, their optical characteristics shall hardly be varied from
one another but substantially remain identical in view of practical
use.
57. As the resin body 211 of the optical system unit for optical
transceiver 201 has been formed to a desired shape, the distance
between the convex lenses 212 and 213 and their corresponding light
emitting device 216 and light receiving device 217 respectively is
measured to determine an ideal length. For setting the distance to
the desired length, the upper step portion 215A and the lower step
portion 215B are spatially positioned by adjusting the angle of
bending of the lead frame 215. More specifically, the lead frame
215 is adjusted in the angle of its bending to set the difference
in the height (along the axial direction of the optical fibers 203
and 204) between the upper step portion 215A and the lower step
portion 215B to a desired value. Also, the vertical position of the
lead frame 215 itself is adjusted to determine an optimum distance
between the two convex lenses 212 and 213 on the upper and lower
step portions 215A and 215B in combination with the above described
angular setting. Accordingly, in case that the two convex lenses
212 and 213 are found slightly different from each other in the
optical characteristics, their difference can readily be eliminated
by adjusting their relative position, thus improving the coupling
effectiveness. The lead frame 215 after the adjustment is then
encapsulated in a molded resin material to form the resin body
211.
58. Moreover, the optical system unit for optical transceiver 201
of this embodiment employs no resin-made mirrors such as shown in
FIG. 10. It is hence free from the disadvantage that the mirrors
may be turned or deformed and dislocated from their optical axes
when the resin body 211 is thermally expanded or compacted by an
abrupt change in the ambient temperature.
Second Embodiment
59. FIG. 4 illustrates a cross section of an optical system unit
for optical transceiver of the second embodiment of the present
invention with the coupling end of a fiber optic cable located
opposite. In FIG. 4, like components are denoted by like numerals
as those shown in FIG. 1 and will be described in no more
detail.
60. In the optical system unit for optical transceiver 201A of the
second embodiment, the two convex lenses 212 and 213 provided
integrally on a resin body 211A are identical to those of the first
embodiment. The resin body 211A contains two, first and second,
lead frames 301 and 302 which replace the single lead frame 215
shown in FIG. 3. The light emitting device 216 is mounted on the
first lead frame 301 and connected by a wire 221 to the
transmission signal line 219. While the second lead frame 302 is
separately disposed beneath the first lead frame 301, the light
receiving device 217 is mounted on the second lead frame 302 so as
to face the convex lens 213. More particularly the first lead frame
301 has a window-like opening provided therein across the optical
path between the convex lens 213 and the light receiving device 217
for clearing the beam of light released from the reception optical
fiber 204.
61. The second lead frame 302 is arranged of an L shape in the
cross section of which one end 302A facing the convex lens 212 is
bent upwardly at a right angle. The one end 302A functions to
shield components of the light which are emitted from the light
emitting device 216, reflected at the interior of the resin body
211A, and directed towards the light receiving device 217 and to
eliminate the effect of noises generated by a relatively large flow
of current running in the transmission signal line 219. The other
end of the second lead frame 302 opposite to the one end 302A
extends beyond the light receiving device 217 and has an amplifier
IC (integrated circuit) 305 mounted thereon. The amplifier IC 305
is connected by a wire 307 to the light receiving device 217 for
amplification of an electrical signal produced by photoelectric
conversion of the light receiving device 217. In other words, as
the two perforation lines 231 and 232 (FIG. 3) of the first
embodiment for bending to a shape are not used in the second
embodiment, the second lead frame 302 is generously increased in
the horizontal area orthogonal to the axial direction of the
transmission optical fiber 203 and the reception optical fiber 204
and can thus support an extra chip such as the amplifier IC.
Third Embodiment
62. FIG. 5 illustrates a cross section of an optical system unit
for optical transceiver of the third embodiment of the present
invention with the coupling end of a fiber optic cable located
opposite. In FIG. 5, like components are denoted by like numerals
as those shown in FIGS. 1 and 4 and will be described in no more
detail.
63. In the optical system unit for optical transceiver 201B of the
third embodiment, the first lead frame 301 is identical in the
structure to that of the second embodiment shown in FIG. 4. The
second lead frame 302 of the second embodiment which is bent
upwardly at the one end 302A is however replaced by a second lead
frame 302B which is substantially planer. In particular, a
shielding sheet 321 is provided in parallel with and between the
first lead frame 301 and the second lead frame 302B as spaced from
both. The shielding sheet 321 is made of a conductive material such
as a metal and its one end is projected out from a resin body 211B
at this side of the sheet of paper and connected to the ground by a
grounding wire 322. The shielding sheet 321, like the first lead
frame 301, has a window-like opening provided therein to face the
reception optical fiber 204. This opening allows the beam of light
to pass from the reception optical fiber 204 to the light receiving
device 217 without shielding.
64. The shielding sheet 321 functions to shield components of the
light emitted from the light emitting device 216, reflected in the
interior of the resin body 211B, and received as noises by the
light receiving device 217 and to electrically block noises
generated by a relatively large flow of current running in the
transmission signal line 219. Accordingly, the one end 302A of the
second lead frame 302 shown in FIG. 4 is unnecessary in the second
lead frame 302B.
65. In the third embodiment, the three different sheets (the first
lead frame 301, the second lead frame 302B, and the shielding sheet
321) are embedded at different locations and heights in the resin
body 211B by molding with a resin material so that their edge
portions not shown are projected out from the resin body 211B. The
edge portions are then trimmed off to form the resin body 211B. The
tree sheets 301, 302B, and 321 can, with no difficulty, be
positioned accurately and embedded in the resin material by a known
molding technique. The resin body 211A of the second embodiment may
also be fabricated by the same technique.
Fourth Embodiment
66. FIG. 6 illustrates a cross section of an optical system unit
for optical transceiver of the fourth embodiment of the present
invention with the coupling end of a fiber optic cable located
opposite. In FIG. 6, like components are denoted by like numerals
as those shown in FIGS. 1, 4, and 5 and will be described in no
more detail.
67. In the optical system unit for optical transceiver 201C of the
fourth embodiment, the first lead frame denoted by 301A is embedded
in a resin body 211C, but not the second lead frame, as
differentiated from the second and third embodiments. The light
emitting device 216 is mounted on the first lead frame 301A so as
to face the fiber optic cable 205 as similar to the first to third
embodiments. The light emitting device 216 is connected by a wire
221 to the transmission signal line 219 which is disposed flush
with the first lead frame 301A. The reception signal line 220 is
also provided flush with the first lead frame 301A.
68. The first lead frame 301A of the fourth embodiment has an
opening 341 provided therein to face the reception optical fiber
204 as sized slightly smaller than that of the first lead frame 301
of the second embodiment (FIG. 4). A light receiving device 342 of
back-side reception is mounted to the back side of the first lead
frame 301A, opposite to the front or reception optical fiber 204
side, so as to face the reception optical fiber 204 across the
opening 341. The light receiving device 342 of back-side reception
type is a device having external terminals mounted on the side
thereof opposite to the light receiving side. As the light
receiving device 342 of back-side reception type is fixedly mounted
by soldering or adhesion to the back side of the first lead frame
301A, its external terminals (not shown) on the back side are
connected by wire bonding of wires 222 to the reception signal line
220.
69. In the optical system unit for optical transceiver 201C of the
fourth embodiment, the light emitting device 216 and the light
receiving device 342 of back-side reception type are mounted on the
back side of the first lead frame 301A. Assuming that the distance
along the height between the light emitting surface and the light
receiving surface is d.sub.1, the thickness of the light emitting
device 216 is a.sub.1, and the thickness of the first lead frame
301A is b.sub.1, their relationship is expressed by Equation 1.
d.sub.1=a.sub.1+b.sub.1 (1)
70. The distance d.sub.1 between the light emitting surface and the
light receiving surface focused by the two convex lenses 212 and
213 respectively can favorably be determined after fabrication of
the resin body 211C by adjusting the thickness a.sub.1 of the light
emitting device 216 and the thickness b.sub.1 of the first lead
frame 301A. If the sum of a.sub.1 and b.sub.1 is smaller than the
distance d.sub.1, a spacer may be disposed between the light
emitting device 216 and the first lead frame 301A or between the
light receiving device 342 of back-side reception type and the
first lead frame 301A, or two spacers between those members so that
the distance d.sub.1 is equal to the thickness sum of the three
members. As a result, the resin body 211C will be simple in the
arrangement. Also, unwanted components of the light from the light
emitting device 216 will successfully be blocked, It is apparent
that unwanted electrical noises can be minimized by connecting the
first lead frame 301A by an unshown grinding wire to the
ground.
Fifth Embodiment
71. FIG. 7 illustrates a cross section of an optical system unit
for optical transceiver of the fifth embodiment of the present
invention with the coupling end of a fiber optic cable located
opposite. In FIG. 7, like components are denoted by like numerals
as those shown in FIGS. 1, 4, 5, and 6 and will be described in no
more detail.
72. In the optical system unit for optical transceiver 201D of the
fifth embodiment, a first lead frame 301B and a second lead frame
302C are bonded to each other and embedded in a resin body 211D.
The light emitting device 216 is mounted on the first lead frame
301B so as to face the transmission optical fiber 203 and to be
spaced by a certain distance from the convex lens 212. The light
emitting device 216 is connected by a wire 221 to the transmission
signal line 219 which is disposed flush with the first lead frame
301B. The first lead frame 301B has a window-like opening 341
provided therein so as to face the reception optical fiber 204 as
similar to those of the second and third embodiments.
73. The second lead frame 302C also has an opening 361 provided
therein at the same position of but slightly smaller in the size
than the window-like opening 341. Provided just beneath the two
openings 341 and 361 is a light receiving device 342 of back-side
reception type which is more specifically mounted on the back side
of the second lead frame 302C with its light receiving side up so
as to face the fiber optic cable 205. The light receiving device
342 of back-side reception type is connected by a wire 222 to the
reception signal line 220 which is disposed flush with the second
lead frame 302C.
74. In the optical system unit for optical transceiver 201D of the
fifth embodiment, the light emitting device 216 is mounted on the
front side of the first lead frame 301B while the light receiving
device 342 of back-side reception type is mounted on the back side
of the second lead frame 302C. Accordingly, assuming that the
distance along the height between the light emitting surface and
the light receiving surface is d.sub.2, the thickness of the light
emitting device 216 is a.sub.2, the thickness of the first lead
frame 301B is b.sub.2, and the thickness of the second lead frame
302C is c.sub.2, their relationship is expressed by Equation 2,
d.sub.2=a.sub.1+b.sub.2+c.sub.2 (2)
75. The distance d.sub.2 between the light emitting surface and the
light receiving surface focused by the two convex lenses 212 and
213 respectively can favorably be determined after fabrication of
the resin body 211D by adjusting the thickness a.sub.2 of the light
emitting device 216, the thickness b.sub.2 of the first lead frame
301B and the thickness c.sub.2 of the second lead frame 302C. If
the sum of a.sub.2, b.sub.2, and c.sub.2 is smaller than the
distance d.sub.2, a spacer may be disposed between the light
emitting device 216 and the first lead frame 301B, between the
first lead frame 301B and the second lead frame 302C, or between
the second lead frame 302C and the light receiving device 342 of
back-side reception type, or two or more spacers between their
members so that the distance d.sub.2 is equal to the thickness sum
of the their members. As a result, the resin body 211D will be
simple in the arrangement. Also, unwanted components of the light
from the light emitting device 216 will successfully be blocked. It
is apparent that unwanted electrical noises can be minimized by
connecting the first lead frame 301B by an unshown grinding wire to
the ground.
Sixth Embodiment
76. FIG. 8 illustrates a cross section of an optical system unit
for optical transceiver of the sixth embodiment of the present
invention with the coupling end of a fiber optic cable located
opposite. In FIG. 8, like components are denoted by like numerals
as those shown in FIGS. 1 and 4 will be described in no more
detail.
77. In the optical system unit for optical transceiver 201E of the
sixth embodiment, a lead frame 381 is embedded in the lower half of
a resin body 211D to extend in parallel with the sheet of paper.
The lead frame 381 of a sheet form has a slope-sided notch 383
provided in the upper edge thereof to face the reception optical
fiber 204. A light receiving device 384 of side reception type is
fixedly mounted on the lead frame 381 so that its light receiving
side coincides with the bottom side of the notch 383. Also, a light
emitting device 385 of side emission type is so positioned that its
light emitting side is aligned with the upper edge of the lead
frame 381 and faces the transmission optical fiber 203. At the
position, the light emitting device 1 as is fixedly secured to the
lead frame 381.
78. The cross section of the optical system unit for optical
transceiver 201E shown in FIG. 8 is taken in parallel with the
sheet of paper just in front of the lead frame 381. FIG. 8 hence
illustrates the resin material over the lead frame 381 removed
off.
79. The lead frame 381 has two more notches provided in the lower
edge thereof for accommodating a transmission signal pin 388 and a
reception signal pin 389 respectively which are projected partially
from the lower side of the resin body 211D. The transmission signal
pin 388 is connected by a wire 391 to the light emitting device 385
of side emission type while the reception signal pin 389 is
connected by a wire 392 to the light reception device 384 of side
emission type. While the transmission signal pin 388 and the
reception signal pin 389 are illustrated one single pin each, they
may be provided two or more which correspond to a number of
terminals on the light emitting device 385 of side emission type
and the light receiving device 384 of side reception type and
arranged at equal intervals in a row in the resin body 211D.
80. The light emitting device 385 of side emission type used in the
sixth embodiment may preferably be a laser diode (LD) or the like.
The light receiving device 384 of side reception type may
preferably be a photo-diode of waveguide type. The light emitting
device 385 of side emission type is optically coupled via the
convex lens 212 to the transmission optical fiber 203 of MT type
ferrule while the light receiving device 384 of side reception type
is optically coupled via the convex lens 213 to the reception
optical fiber 204 of MT type ferrule.
81. Although the two convex lenses 212 and 213 described in each
embodiment are designed to be identical to each other in the
optical characteristics, they when made by molding of a resin
material are not intended to have the identical characteristics. It
is probable that the two lenses are very similar in the optical
characteristics or different more or less in the focal distance due
to the accuracy of molds employed and the conditions of molding
process. The present invention allows the light emitting device and
the light receiving device to be positioned separately in relation
to their respective lenses and can thus overcome the above
mentioned discrepancies with its specific means for modifying the
lead frame(s) in location. Accordingly, when the two resin lenses
for transmission and reception of optical signals are differed from
each other by some extent in the optical characteristic, they may
be handled as identical ones. This may also permit the proved
measurements of various conventional resin lenses to be directly
utilized for designing without modification. Such lenses can be
formed by a known molding method as parts of the optical system
unit for optical transceiver made of a resin material, hence
contributing to the reduction of the labor for designing of the
optical system unit.
82. As set forth above, the present invention according to claims 1
to 8 is characterized in that the transmission lens and the
reception lens are formed integrally by a resin material which is
transparent for the applied wavelengths of light so as to face the
transmission optical fiber and the reception optical fiber
respectively of a fiber optic cable and the distance between the
light emitting device and the light receiving device is determined
on the basis of the optical characteristic of the two lenses.
Accordingly, the optical system becomes simpler in the arrangement
with no use of mirrors. In addition, the transmission lens and the
reception lens can commonly be used as are identical in the optical
characteristics and the data of conventional similar lenses can be
utilized for designing. This will facilitate the designing process
of the system unit hence contributing to the speed-up and the cost
down of the development and manufacturing. Moreover, as no mirrors
are used, the system unit will remain stable regardless of changes
in the ambient temperature.
83. As defined in claim 1, the single lead frame is bent to a shape
having two steps on which the light emitting device and the light
receiving device are mounted respectively. The bent can
successfully shield unwanted components of the light emitted from
the light emitting device. Also, the difference in the distance to
the lens between the light emitting device and the light receiving
device can easily be controlled by varying the angle of bending the
lead frame. Furthermore, as a number of its components is
minimized, the system unit can be manufactured at a lower cost.
84. As defined in claim 2, the lead frame according to claim 1 has
the rows of perforations provided therein along the bending lines.
Accordingly, the light emitting device and the light receiving
device mounted on the lead frame are free from excessive stress
developed during the bending process and can thus be prevented from
unwanted physical damage.
85. As defined in claim 3, the two, first and second, lead frames
are embedded in the resin body so that the distance between the
light emitting device and the light receiving device can be
determined arbitrarily and separately depending on the optical
characteristics of the two resin lenses. As compared with the
single lead frame, the two lead frames can provide more rooms for
installation of the components which are thus increased in the size
and number.
86. As defined in claim 4, the two lead frames are placed one over
the other while one of them having an opening provided therein for
clearing the optical path. This allows the spatial arrangement of
the two lead frames to be less limitable when capsulated in the
resin material, whereby the components can be mounted readily and
accurately.
87. As defined in claim 5, each of the two lead frames of the
optical system unit for optical transceiver according to claim 4
has a window-like opening provided therein at the same position so
that the light receiving device of back-side reception type is
mounted to the back side of the lower lead frame with its light
receiving surface exposed to the optical fiber across the
window-like openings of the two lead frames. Accordingly, the
freedom for using the device can be improved. In addition, the
positional relation between the light emitting device and the light
receiving device can steadily be determined by controlling the
thickness of the two lead frames which are joined to each other,
hence permitting the optical system unit for optical transceiver to
be readily fabricated in a simple arrangement.
88. As defined in claim 6, the shielding sheet is provided between
the two, first and second, lead frames and connected to the ground
to eliminate electrical and optical noises. Accordingly, the
optical system unit for optical transceiver can be reduced in the
size and improved in the shielding effect.
89. As defined in claim 7, the lead frame is arranged at a right
angle to the plane on which the lead frames according to claims 1
to 6 are arranged, thus allowing the light emitting device of side
emission type and the light receiving device of side reception type
to be employed.
90. As defined in claim 8, the optical system unit for optical
transceiver can be fabricated in a smaller arrangement for coupling
with a plurality of fiber optic cables.
* * * * *