U.S. patent number RE36,886 [Application Number 09/087,857] was granted by the patent office on 2000-10-03 for fiber optic module.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Shin Ishibashi, Tomiya Miyazaki, Hideyuki Nagao.
United States Patent |
RE36,886 |
Ishibashi , et al. |
October 3, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Fiber optic module
Abstract
A fiber optic module includes a connector connected to a mother
board of a host computer, an LD semiconductor IC for converting
serial data received from the mother board to an LD electric signal
for a laser diode, an LD module for converting the LD electric
signal to an LD optical signal, a PD module for converting a
photodiode optical signal to a PD electric signal, a PD
semiconductor IC for converting the PD electric signal to PD serial
data, a circuit board having the connector and carrying LD
semiconductor IC and PD semiconductor IC, and LD shielding plate
and a PD shielding plate for electrically shielding the LD module
and the PD module, respectively, a .[.first frame and a second.].
frame for holding the circuit board, LD module and PD module. In
the fiber optic module, the connector is of a surface mounting
type, leads of the LD and PD modules are connected to a side of the
circuit board mounted with the connector, the circuit board has an
LD variable resistor for adjusting a drive current of the LD
module, the LD variable resistor is provided to a side of the
circuit board opposite to the connector, the circuit board has a PD
variable resistor provided to the side of the circuit board
opposite to the connector for detecting a signal of the PD module,
3 signal processing semiconductor ICs or less are provided.
Inventors: |
Ishibashi; Shin (Fukuoka,
JP), Nagao; Hideyuki (Fukuoka, JP),
Miyazaki; Tomiya (Fukuoka, JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Kadoma, JP)
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Family
ID: |
13893999 |
Appl.
No.: |
09/087,857 |
Filed: |
June 1, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
372078 |
Jan 12, 1995 |
05596663 |
Jan 21, 1997 |
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Foreign Application Priority Data
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Apr 25, 1994 [JP] |
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6-086691 |
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Current U.S.
Class: |
385/92;
361/785 |
Current CPC
Class: |
G02B
6/4246 (20130101); G02B 6/4277 (20130101); G02B
6/4292 (20130101); H04B 10/801 (20130101) |
Current International
Class: |
G02B
6/42 (20060101); H04B 10/00 (20060101); G02B
006/255 (); G02B 006/00 (); G02B 006/36 () |
Field of
Search: |
;385/88-94
;361/761,783,785,760 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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437161 |
|
Jul 1991 |
|
EP |
|
624962 |
|
Nov 1994 |
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EP |
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3218134 |
|
Sep 1991 |
|
JP |
|
2087681 |
|
Jul 1991 |
|
GB |
|
Primary Examiner: Ullah; Akm E.
Attorney, Agent or Firm: Venable Frank; Robert J. Wood;
Allen
Claims
What is claimed is:
1. A fiber optic module comprising:
a connector for connection with a mother board;
a laser diode electric signal conversion means for converting
serial data received from said mother board to an laser diode
electric signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said connector is of a surface mounting type.
2. A fiber optic module as set forth in claim 1, wherein leads of
said laser diode and photo diode modules are connected to a surface
of said circuit board provided thereon with said connector.
3. A fiber optic module as set forth in claim 2, further comprising
an laser diode variable resistor for adjusting a drive current of
said laser diode module and wherein said laser diode variable
resistor is provided on a surface of said circuit board opposed to
said surface having said connector thereon.
4. A fiber optic module as set forth in claim 2, further comprising
a photo diode variable resistor for detecting a signal of said
photo diode module and wherein said photo diode variable resistor
is provided on a surface of said circuit board opposed to said
surface having said connector thereon.
5. A fiber optic module as set forth in claim 1, wherein said photo
diode electric signal conversion means includes a plurality of
semiconductor integrated circuits.
6. A fiber optic module as set forth in claim 1, wherein said
circuit board measures 17 mm through 25.4 mm wide, 30 mm through
and 50 mm long.
7. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein outline dimensions of said fiber optic module are 19 mm
through 25.4 mm wide, 45 mm through 65 mm high and 9 mm through
25.4 mm .[.high.]. .Iadd.long.Iaddend..
8. A fiber optic module as set forth in claim 7, further comprising
a casing, said casing comprising said .[.first and second frames.].
.Iadd.frame .Iaddend.forms an outside casing.
9. A fiber optic module as set forth in claim 7, wherein said
.[.first and second frames are.]. .Iadd.frame is .Iaddend.made of
resin material.
10. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said module comprises mounting means for mounting said
.[.first and second frames.]. .Iadd.frame .Iaddend.to said mother
board.
11. A fiber optic module as set forth in claim 10, wherein said
mounting means includes a screw.
12. A fiber optic module as set forth in claim 11, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.further comprising a first frame openings provided in
said first frame .Iadd.part.Iaddend., a second frame openings
provided in said second frame .Iadd.part.Iaddend., a circuit board
openings provided in said circuit board, and a mother board
openings provided in said mother board, and wherein screws are
inserted into said first openings, second frame openings, said
circuit board openings and said mother board openings to cause said
first frame .Iadd.part.Iaddend., said second frame
.Iadd.part.Iaddend., said circuit board and said mother board to be
mutually fixed.
13. A fiber optic module as set forth in claim 12, wherein said
first frame openings is smaller than said second frame openings and
said circuit board openings and said mother board openings have
substantially the same diameter as said second frame opening.
14. A fiber optic module as set forth in claim 10, wherein said
screws have an effective diameter of 1.3 mm or more.
15. A fiber optic module as set forth in claim 12, wherein 3 of
said first frame openings are provided in said first frame
.Iadd.part .Iaddend.and said first frame openings are arranged to
form a substantially isosceles triangle.
16. A fiber optic module as set forth in claim 12, wherein said
first frame openings are used also as reference holes for parts
inspection of said first frame .Iadd.part .Iaddend.and said second
frame openings are used also as reference holes for parts
inspection of said second frame .Iadd.part.Iaddend..
17. A fiber optic module as set forth in claim 11, wherein said
screws are tapping screws.
18. A fiber optic module as set forth in claim 10, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.wherein pins erected on at least one of said first and
second .[.frames.]. .Iadd.frame parts .Iaddend.are used as said
mounting means.
19. A fiber optic module as set forth in claim 18, wherein pins
erected only on said second frame .Iadd.part .Iaddend.are used as
said mounting means.
20. A fiber optic module as set forth in claim 19, further
comprising first frame openings provided in said first frame
.Iadd.part.Iaddend., a circuit board openings provided in said
circuit board, and a mother board openings provided in said mother
board, and wherein screws are inserted into said first frame
openings, said circuit board openings and said mother board
openings to cause said first frame .Iadd.part.Iaddend., said
circuit board and said mother board to be mutually fixed.
21. A fiber optic module as set forth in claim 20, wherein said
first frame openings are larger than a diameter of said pin and
said circuit board openings and said mother board openings have
substantially the same diameter as said first frame openings.
22. A fiber optic module as set forth in claim 19, wherein said pin
has a diameter of 1.3 mm or more.
23. A fiber optic module as set forth in claim 19, wherein said pin
is made of metallic material.
24. A fiber optic module as set forth in claim 19, wherein said pin
is integrally formed with said second frame .Iadd.part .Iaddend.or
press fitted therein.
25. A fiber optic module as set forth in claim 20, wherein 3 of
said first frame openings are provided in said first frame
.Iadd.part .Iaddend.and said first frame openings are arranged to
form a substantially isosceles triangle.
26. A fiber optic module as set forth in claim 20, wherein said
first frame openings are used also as reference holes for parts
inspection of said first frame .Iadd.part .Iaddend.and said pins
are used also as reference holes for parts inspection of said
second frame .Iadd.part.Iaddend..
27. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said circuit board is temporarily fixed to .[.at least one
of said first and second frames.]. .Iadd.said frame.Iaddend..
28. A fiber optic module as set forth in claim 27, wherein said
temporary fixing means is a snap-fit mechanism.
29. A fiber optic module as set forth in claim 28, wherein said
circuit board is temporarily fixed at an end thereof by said
snap-fit mechanism.
30. A fiber optic module as set forth in claim 27, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.wherein an elastic arm is provided to at least one of
said first and second .[.frames.]. .Iadd.frame parts .Iaddend.and
said circuit board is temporarily fixed to the other frame by said
elastic arm.
31. A fiber optic module as set forth in claim 27, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.wherein said circuit board is temporarily fixed at a
front part thereof by a snap-fit mechanism and said circuit board
is temporarily fixed to .[.the other frame.]. .Iadd.one of said
first and second frame parts .Iaddend.at a rear part thereof by an
elastic arm.
32. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said module further comprises supporting means for
tightening to fix .[.said first and second frames.]. .Iadd.said
frame .Iaddend.and said mother board from their outer
periphery.
33. A fiber optic module as set forth in claim 32, wherein said
supporting means is made of metallic plate.
34. A fiber optic module as set forth in claim 33, wherein said
metallic plate is provided in its both ends with recesses and said
recesses are rotated to tightening fix said metallic plate.
35. A fiber optic module as set forth in claim 32, wherein said
supporting means is positioned at a position opposed to said laser
diode and photo diode modules.
36. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
first and second .[.frames.]. .Iadd.frame parts .Iaddend.for
holding said circuit board, said laser diode module and said photo
diode module,
wherein said module further includes a cover for covering an
externally exposed part of said circuit board therewith.
37. A fiber optic module as set forth in claim 36, wherein said
cover is made of resin material.
38. A fiber optic module as set forth in claim 36, wherein said
cover is made of metallic material.
39. A fiber optic module as set forth in claim 36, wherein said
cover is made in the form of said first frame
.Iadd.part.Iaddend..
40. A fiber optic module as set forth in claim 36, wherein said
cover is provided therein with an opening.
41. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said module further comprises indication parts indicative
of a safety certification .[.and a place of.]. .Iadd.and/or
.Iaddend.production provided .[.respectively onto said first and
second frames.]. .Iadd.on said frame.Iaddend..
42. A fiber optic module as set forth in claim 41, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.wherein said indication part provided onto said first
frame .Iadd.part .Iaddend.is opposed to said indication part
provided onto said second frame .Iadd.part.Iaddend..
43. A fiber optic module as set forth in claim 42, wherein said
first and second .[.frames.]. .Iadd.frame parts .Iaddend.have a
recess and said indication parts are provided to said recesses.
44. A fiber optic module as set forth in claim 41, wherein said
indication parts are seal labels.
45. A fiber optic module as set forth in claim 41, wherein said
indication parts are provided integrally to said .[.first and
second frames respectively.]. .Iadd.frame.Iaddend..
46. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein a data transmission rate of said optical signal is 130
Mbits/s or more.
47. A fiber optic module as set forth in claim 46, wherein the data
transmission rate of said optical signal is 200 Mbits/s or
more.
48. A fiber optic module as set forth in claim 46, wherein the data
transmission rate of said optical signal is 500 Mbits/s or
more.
49. A fiber optic module as set forth in claim 46, wherein the data
transmission rate of said optical signal is 1000 Mbits/s or
more.
50. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said fiber optic module further includes a module cap to be
inserted into light outlet and inlet openings defined by said
.[.first and second frames.]. .Iadd.frame .Iaddend.along a light
inlet and outlet direction.
51. A fiber optic module as set forth in claim 50, .Iadd.wherein
said frame comprises a first frame part and a second frame part,
and .Iaddend.wherein said module cap has cap fixing means engaged
with part of said first and second .[.frames.]. .Iadd.frame parts
.Iaddend.and fixed to at least one of said first and second
.[.frames.]. .Iadd.frame parts.Iaddend..
52. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
.[.first and second frames.]. .Iadd.a frame .Iaddend.for holding
said circuit board, said laser diode module and said photo diode
module,
wherein said fiber optic module includes a shielding member for
shielding at least one of said laser diode and photo diode
modules.
53. A fiber optic module as set forth in claim 52, wherein a
shielding plate for exclusive use of said laser diode module and a
shielding plate for exclusive use of said photo diode module.
54. A fiber optic module as set forth in claim 52, wherein .[.at
least one of said first and second frames.]. .Iadd.said frame
.Iaddend.is provided integrally with a shielding plate.
55. A fiber optic module comprising:
a connector for connection with a mother board;
laser diode electric signal conversion means for converting serial
data received from said mother board to an laser diode electric
signal for a laser diode;
an laser diode module for converting said laser diode electric
signal to an laser diode optical signal;
a photo diode module for converting a photodiode optical signal to
a photo diode electric signal;
photo diode electric signal conversion means for converting said
photo diode electric signal to photo diode serial data;
a circuit board for carrying thereon said connector, said laser
diode electric signal conversion means, said laser diode module and
said photo diode module; and
first and second .[.frames.]. .Iadd.frame parts .Iaddend.for
holding said circuit board, said laser diode module and said photo
diode module,
wherein elastic pawls to be engaged with an optical fiber plug are
provided to at least one of said first and second .[.frames.].
.Iadd.frame parts .Iaddend.and said pawls are provided at their
root parts with first projections extended toward the other
frame.
56. A fiber optic module as set forth in claim 55, wherein second
projections for protecting said first projections are provided to
an opposite frame .Iadd.part .Iaddend.being opposite to the frame
.Iadd.part .Iaddend.provided with said first projections.
57. A fiber optic module as set forth in claim 55, wherein said
first and second .[.frames.]. .Iadd.frame parts .Iaddend.and said
pawls are made of resin material.
58. A fiber optic module comprising:
a connector for connecting with a mother board of a computer;
a first semiconductor integral circuit for converting a first
parallel data provided from the mother board into a first serial
data for a laser diode;
a second semiconductor integral circuit for converting said first
serial data for the laser diode converted by said first
semiconductor integral circuit into a first electrical signal;
a laser diode module including a laser diode for converting said
first electrical signal for the laser diode into a first optical
signal of the laser diode;
a photodiode module including a photodiode for converting a second
optical signal received by said photodiode into a second electrical
signal of the photodiode;
a third semiconductor integral circuit for converting said second
electrical signal of the photodiode into a second serial data of
the photodiode;
a fourth semiconductor integral circuit for converting said second
serial data of the photodiode converted by said third semiconductor
integral circuit into a second parallel data;
a circuit board for furnishing with said connector, said first
semiconductor integral circuit, said second semiconductor integral
circuit, said third semiconductor integral circuit and said fourth
semiconductor integral circuit;
a first shielding plate for electrically shielding said laser diode
module;
a second shielding plate for electrically shielding said photo
diode module; .Iadd.and .Iaddend.
.[.a first frame for holding said circuit board, said laser diode
module and said photo diode module; and
a second frame for cooperating with said first frame to hold.].
.Iadd.a frame for holding .Iaddend.said circuit board, said laser
module and said photo diode module.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a fiber optic module which can be
used in such a device as to perform data transfer between
apparatuses.
There has been so far known such a fiber optic module as shown in
FIGS. 17-19 (disclosed in JP-A-3218134). FIG. 17 is a plan view of
a prior art fiber optic module which comprises laser diode (LD)
modules 1 for transmitting an optical signal onto a printed circuit
board 3 having a width of 76 mm and a length of 75 mm, photodiode
(PD) modules 2 for receiving the optical signal, semiconductor ICs
4 and 5 for converting the optical signal into an electric signal,
and a connector 6 for transfer of the electric signal to a mother
board (not shown in the drawing).
FIG. 18 is a cross-sectional view of a major part of a lower frame
for the prior art fiber optic module. The prior art fiber optic
module is fixed to the mother board (not shown) by means of a
spacer 8 and a J-letter shaped clip 9 both formed in a lower frame
7b.
FIG. 19 is a cross-sectional view showing a holding mechanism of
the prior art fiber optic module to be held to the circuit board.
More specifically, the circuit board 3 is inserted into a rear part
of the lower frame 7b and then held by the upper and lower frames
7a and 7b.
However, the above prior art has had several problems which
follow.
1) The electric signals are transferred on a parallel data basis,
and then even though each of parallel signals consists of, e.g., 8
bits, the number of signal lines transferring the parallel signals
as well as other signals becomes as many as 50, which requires the
large size of connectors and semiconductor ICs for serial/parallel
conversion, which results in that the size of the entire unit must
be inevitably made large. Further, not only the large size of this
unit per se goes against a recent tendency of the rapid downsizing
movement of host computer but this also largely limits the design
flexibility of mother board for system manufacturers.
2) The fixation between the fiber optic module and mother board in
the prior art is effected by means of the J-letter shaped clip 9 in
the form of a resin leg extended from the lower frame 7b as already
explained in connection with FIG. 18. This requires a large hole as
an opening for fixation in the mother board, whereby the design
flexibility of the mother board by the system manufacturer is
largely limited. Further, since the prior art has such a structure
that a load caused by the force derived by mounting and dismounting
of the optical fiber is applied to the J-letter shaped clip 9 and
the lead (not shown) of the connector 6, this causes a breakage of
the J-letter shaped resin-clip 9 made from resin or a poor
connection of the connector lead, with the result of reduction in
the reliability of the fiber optic module.
Furthermore, for the purpose of avoiding any stress applied to the
leads of the LD modules 1 and PD modules 2, the accuracy of each of
the parts must be increased and thus parts management (such as
parts acceptance inspection) becomes necessary, which make it
difficult to obtain a low-cost fiber optic module.
3) The prior art fiber optic module is fixed by soldering the
connector 6 to the circuit board 3 and thereafter the signal lines
of the connector 6 are directly connected to the mother board by
soldering. The necessity of these works hinders realization of a
low-cost fiber optic module.
4) In the method for holding the circuit board 3 as shown in FIG.
19, a warpage occurs in the circuit board 3, which remarkably
deteriorates the reliability of the circuit board 3. Further, the
holding method shown in FIG. 19 requires a sufficient length of the
circuit board 3 itself and a sufficient circuit-board holding
length L, which hinders realization of a miniaturized fiber optic
module.
5) Since most area of the circuit board 3 is in its exposed state,
when a worker handles the prior art fiber optic module or a user
mounts the prior art fiber optic module onto the mother board, the
prior art fiber optic module is susceptible to electrostatic
destruction, which leads to poor reliability and costliness of the
fiber optic module.
6) During a long-term storage, dust or foreign matter invades into
the LD and PD modules into which optical fibers are to plug, which
causes improper or poor connection between the optical fiber and
the module, thus resulting in remarkable reduction in the
reliability of the fiber optic module.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a
fiber optic module which can solve the above problems in the prior
art and can be made compact in size, high in the design flexibility
of mother board, low in cost and high in reliability.
In accordance with an aspect of the present invention, the above
object is attained by providing a fiber optic module which includes
a connector connected to a mother board of a host computer, an LD
semiconductor IC for converting serial data received from the
mother board to an LD electric signal for a laser diode, an LD
module for converting the LD electric signal to an LD optical
signal, a PD module for converting a photodiode optical signal to a
PD electric signal, a PD semiconductor IC for converting the PD
electric signal to PD serial data, a circuit board having the
connector and carrying LD semiconductor IC and PD semiconductor IC,
and LD shielding plate for electrically shielding the LD module, a
PD shielding plate for electrically shielding the PD module, a
.[.first.]. frame .Iadd.comprising a first frame part and a second
frame part .Iaddend.for holding the circuit board, LD module and PD
module.[., and a second frame for holding the circuit board, LD
module and PD module.].. In the fiber optic module, the connector
may be of a surface mounting type, leads of the LD and PD modules
may be connected to a side of the circuit board mounted with the
connector, the circuit board may have an LD variable resistor for
adjusting a drive current of the LD module, the LD variable
resistor may be provided to a side of the circuit board opposite to
the connector, the circuit board may have a PD variable resistor
for detecting a signal of the PD module, the PD variable resistor
may be provided to the side of the circuit board opposite to the
connector, 3 signal processing semiconductor ICs or less may be
provided, an outline configuration of the circuit board may measure
17 mm through 25.4 mm wide and 30 mm through 50 mm long, the
outline dimensions of the fiber optic module may be 19 mm through
25.4 mm wide, 45 mm through 65 mm high and 9 mm through 25.4 mm
high, the second frame .Iadd.part .Iaddend.may be provided with
pawls for coupling of the optical signal, the first frame
.Iadd.part .Iaddend.may be provided with projections for protecting
the pawls, the first and second .[.frames.]. .Iadd.frame parts
.Iaddend.may be made of resin material, the first and second
.[.frames.]. .Iadd.frame parts .Iaddend.may have means for holding
the circuit board, the holding means may be a snap-fit mechanism, a
tipmost end of the circuit board may be held by the first and
second .[.frames.]. .Iadd.frame parts.Iaddend., the first frame
.Iadd.part .Iaddend.may have an arm, a recess provided to the arm
may be used to hold at least one rear part of the circuit board,
and the data transmission rate of the optical signal may be 200
Mbits/s or more.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, in a block diagram form, of a fiber
optic module in accordance with a first aspect of the present
invention;
FIG. 2 is a perspective view of a fiber optic module in accordance
with a second aspect of the present invention;
FIG. 3 is an exploded perspective view of a part of a fiber optic
module in accordance with a third aspect of the present
invention;
FIG. 4 is an exploded perspective view of another part of a fiber
optic module in accordance with the third aspect of the present
invention;
FIG. 5 is a cross-sectional view of a major part of a fiber optic
module in accordance with a fourth aspect of the present
invention;
FIG. 6 is a cross-sectional view of a major part of a fiber optic
module in accordance with a fifth aspect of the present
invention;
FIG. 7 is a perspective view of a lower frame .Iadd.part
.Iaddend.for a fiber optic module in accordance with a sixth aspect
of the present invention;
FIG. 8 is a cross-sectional view of a major part of a fiber optic
module in accordance with a seventh aspect of the present
invention;
FIG. 9 is a cross-sectional view of a fiber optic module in
accordance with an eighth aspect of the present invention;
FIG. 10 is a cross-sectional view of a fiber optic module in
accordance with a ninth aspect of the present invention;
FIG. 11 is a perspective view of a fiber optic module in accordance
with a tenth aspect of the present invention;
FIG. 12 is a plan view of a fiber optic module in accordance with
an eleventh aspect of the present invention;
FIG. 13A is an exploded perspective view of a fiber optic module in
accordance with a twelfth aspect of the present invention;
FIG. 13B shows a perspective view of the assembled fiber optic
module of the twelfth aspect of the invention;
FIG. 14 is a perspective view of a fiber optic module in accordance
with a thirteenth aspect of the present invention;
FIG. 15 is a plan view of the fiber optic module in accordance with
the thirteenth aspect of the present invention;
FIG. 16 is a perspective view of a module cap of the fiber optic
module in accordance with the thirteenth aspect of the present
invention;
FIG. 17 is a plan view of a prior art fiber optic module;
FIG. 18 is a cross-sectional view of a major part of a lower frame
.Iadd.part .Iaddend.for the prior art fiber optic module;
FIG. 19 is a cross-sectional view of a major part of how to hold a
circuit board of the prior art fiber optic module.
FIG. 20 is an eye pattern of a random pattern transmitted through
the fiber optic module of the invention;
FIG. 21 shows a bit error rate (BER) of the fiber optic module of
the invention;
FIG. 22 is a circuit diagram of measuring circuit for the bit error
rate; and
FIG. 23 is a block diagram of the fiber optic module of the
fourteenth aspect of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be explained with reference to the
accompanying drawings, in which parts having the same reference
numerals represent identical parts.
Referring first to FIG. 1, there is shown a block diagram of a
fiber optic module in accordance with a first aspect of the present
invention. In FIG. 1, a printed circuit board (which will be
referred to as the PCB, hereinafter) 30 functions to send an
electric signal (serial data) received at a PCB connector 32 to a
laser diode (LD) driver 33 to drive an LD element (not shown and
refer to FIG. 8) located within an LD module 50 and to transmit the
data in the form of an optical signal to an optical fiber (ferule:
not shown) inserted in an opening 52 of the LD module 50. A
photodiode (PD) module 40, on the other hand, receives an optical
signal from an optical fiber (not shown) inserted in an opening 42
of the PD module 40, converts the optical signal to a current
through a PD element (not shown: refer to FIG. 8), and sends the
current to a transformer impedance amplifier part 35a of an
amplifier 35 in the form of a semiconductor IC for conversion of
the current to a voltage. Further, the optical analog signal in the
form of the voltage is converted by a shaping circuit part 35b into
a digital signal and transmitted as serial data to the mother board
through the PCB connector 32. With the fiber optic module of the
present invention, since transfer of an electric signal is carried
out in the form of serial data, the PCB connector 32 requires only
about 22 of signal lines. That is, not only the size of the PCB
connector 32 itself can be made highly compact but the PCB 30 can
also be made compact, which results in that the fiber optic module
can realize reliable data transmission with a speed as high as
above 130 Mbits/s. In this connection, although the amplifier 35
has been made in the form of a single semiconductor IC in the first
aspect of the present invention, the transformer impedance
amplifier part 35a may be made separately from the shaping circuit
part 35b respectively as a single semiconductor IC with
substantially the same effects as the above case.
A high speed data transmission with LD elements emitting 780 nm
wavelength with 5 mW maximum rating voltage, for example. The fiber
optic module of the invention is in conformity of the ANSI x3T9.3
fiber channel standard and performs data transmission rates at 133
Mbits/s, 266 Mbits/s, 531 Mbits/s and 1061 Mbits/s. A typical
performance is shown in FIG. 20. FIG. 20 shows an eye pattern of a
random pattern transmitted at the transmission rate of 531 Mbits/s
through the fiber optic module of the invention. FIG. 20
illustrates a voltage level converted from the optical signal
emitted by LD module 50 via an opto-electric conversion element
having a sufficiently broad wave band as a function of time. The
figure shows optical signal passed through a Bessel filter of 400
MHz observed by an oscilloscope. In FIG. 20, reference Pd
designates the standard amplitude width representing emission
level, Po designates an overshoot permitted in the ANSI x3T9.3
normalized by the value of Pd, and Pu represents a permissible
undershoot normalized by the value of Pd. Comparing with the
permissible overshoot Po and the permissible undershoot Pu, the
optical signal from the fiber optic module of the invention is
surely a desirable signal having a sufficient margin from the
permissible values. Reference Pi shows an eye diagram provided in
the ANSI x3T9.3 being applied on the data of the invention. No
errors shown in the eye diagram certify that the fiber optic module
of the invention has a sufficient margin from the permissible
values. In FIG. 20, a cyclic period of the optical signal of 1.88
ns is drawn for a proper understanding of performance of the
invention at 531 Mbits/s.
FIG. 21 shows a bit error rate (BER) of the fiber optic module of
the invention. FIG. 21 illustrates the bit error rate in a
logarithmic scale as a function of the optical power received by
the optical sensor. The bit error rate is measured by a bit error
rate tester connected with the optical sensor through the fiber
optic module. The measuring circuit is shown in FIG. 22 as an
example. An electrical serial data 93 from the bit error rate
tester 90 is transmitted to LD driver 33 via PCB connector 32. LD
driver 33 converts the electrical serial data to an optical signal
for stimulating LD module 50. The optical signal emitted from LD
module 50 is transmitted to PD module 40 via optical cables 92 and
light attenuator 91. The optical signal transmitted to PD module 40
is then converted to an electric signal by amplifier 35 and
transmitted to bit error rate tester 90 in the form of serial data
output 94 via PCB connector 32. The bit error rate shown in FIG. 21
means a-ratio of serial data 94 passed after fiber optic module
assembly 100 compared with serial data 93 which is before passing
through the assembly 100. For example, when error occurs in one bit
during transmission of 1000 bits of data, the ratio becomes
10.sup.-3. The received power shown in FIG. 21 represents the
intensity of the optical signal incident to PD module 40 shown in
FIG. 22. The optical signal emitted by LD module 50 is variably
regulated by light attenuator 91 in level of an incident optical
signal to control the received power or intensity of the optical
signal transmitted to PD module 40. The diagram of FIG. 21 is
obtained in the manner described above utilizing the measuring
circuit shown in FIG. 22.
In FIG. 21, the actual plotted points are at the received powers of
-20.5 dBm, -20 dBm, -19.5 dBm and -19 dBm only. A linearly
extrapolated line of the above four plotted points shows the
received power at 10.sup.-12 of BER reaches -18.6 dBm, which value
sufficiently clears the minimum received power of -15 dBm
recommended by the ANSI x3T9.3 for satisfying the bit error rate of
10.sup.-12.
Explanation will next be made as to the compact design of the PCB
30 by referring also to FIG. 1.
General expansion slots for insertion of a mother board into a host
computer are designed, in most cases, at intervals of 25.4 mm, in
which case a fiber optic module must be designed adaptive to the
intervals of 25.4 mm so that the module can be mounted horizontally
or vertically to the mother board. In other words, it is desirable
to design the width-directional dimension of the PCB 30 to be
shorter than 25.4 mm.
When the PCB connector 32 has 22 pins (arranged in 2 columns with
11 lines) with pin pitches of 1.27 mm, the connector has a
width-directional dimension of about 14 mm and a longitudinal
dimension of 2.5 mm, which results in that the outline of the PCB
connector 32 including its housing and lead parts (not shown) has a
width-directional dimension of 17 mm and a longitudinal dimension
of 5 mm. The outline of the semiconductors IC (33 and 35) has a
width-directional dimension of 7 mm and a longitudinal dimension of
10 mm (or may have a width-directional dimension of 10 mm and a
longitudinal dimension of 7 mm). When not only the outline
dimensions of the PCB connector 32 and semiconductor ICs but also
the parts mounting to the PCB 30 and the wiring pattern of the PCB
30 are taken into consideration, it is desirable that the outline
of the PCB 30 have a width-directional dimension of 19 mm or more
and a longitudinal dimension of 30 mm or more. Even when the number
of such semiconductor ICs for use in signal processing is increased
up to 3, the longitudinal dimension of the PCB 30 can be designed
to be 50 mm or less. Thus, it is desirable to set the width of the
PCB 30 between 17 mm and 25.4 mm and the length of the PCB 30
between 30 mm and 50 mm. In the first aspect of the present
invention, the PCB 30 is set to have a width of 22.5 mm, a length
of 32 mm (the longest part) and a thickness of 1.6 mm (providing a
mechanical strength), thus realizing a reliable PCB 30. Further,
the PCB connector 32 is of a surface mounting type and only two of
the semiconductor ICs are employed for signal processing, whereby a
small size of PCB 30 is realized. In the first aspect of the
present invention, the thickness of the PCB 30 is not specifically
limited. In this connection, since the use of the surface mounting
type of PCB connector 32 enables minimization of unnecessary
radiation issued from the connector, this is especially useful for
such a compact fiber optic module as in the present aspect.
Shown in FIG. 2 is a perspective view of a fiber optic module in
accordance with a second aspect of the present invention.
Explanation will be made as to the compact design of the fiber
optic module by referring to FIG. 2.
The PCB 30 is held by an upper frame 10 and a lower frame 20 to
form an assembly or fiber optic module. The PCB 30 is mounted
thereon with an LD driver 33 formed as a semiconductor IC for
driving an LD element (refer to FIG. 8), variable resistors 34 for
adjusting a current for driving of the LD element (not shown), and
a PCB connector 32 for connection with a mother board (not shown).
In order to keep constant the average wall thickness of the upper
frame 10, a thin wall part 17 is provided in the upper frame
10.
As already explained even in connection with the compact design of
the PCB 30 of FIG. 1 in the first aspect, expansion slots for
insertion of a mother board into a host computer are arranged, in
many cases, at intervals of 25.4 mm, so that it is necessary to
design a fiber optic module to be mountable to the mother board
horizontally or vertically to the 25.4 mm-interval expansion slots.
Thus, it is desirable that the module have a width-directional
dimension of 25.4 mm at maximum. In the illustrated example, the
PCB 30 is designed to have a width-directional dimension of 17
mm-25.4 mm and a longitudinal dimension of 30 mm-50 mm. In view of
the width-directional dimension, in order to avoid any offset in
the direction perpendicular to the width direction of the PCB 30,
it is desirable that the frame of the fiber optic module be larger
than the width of the PCB 30. For example, when the width of the
frame is 2 mm or more larger than the width of the PCB 30, a step
for offset prevention of
the PCB 30 can be provided in the frame. Accordingly, when
consideration is given to the width-directional dimension of the
PCB 30, the width-directional dimension of the fiber optic module
is designed desirably to be about between 19 mm and 25.4 mm.
Next, with regard to the longitudinal direction, in view of the
fact that the PCB 30 has a longitudinal dimension of 30 mm-50 mm
and the LD module 50 has a length of about 15 mm, the fiber optic
module has a length of 45 mm-65 mm. That is, the longitudinal
dimension of the fiber optic module is set to be desirably about
between 45 mm and 65 mm.
As already explained in connection with the height direction, in
view of the fact that the fiber optic module of the present
invention is to be vertically or horizontally positioned to be
built in between the expansion slots of the host computer, the
height of the module is set to be desirably 25.4 mm or less. When
additional consideration is given to such a situation that two of
the fiber optic modules of the present invention are mounted as
doubly overlapped to the mother board, the module height is set to
be more desirably 12.7 mm or less. Further, when consideration is
given to the wrong insertion preventing mechanism of an optical
fiber plug (not shown) to be fitted into the fiber optic module,
the receptacle of the optical fiber plug, the strength of the
frame, etc., it is more preferable that the fiber optic module have
a height of 9 mm or more. Accordingly, it is preferable for the
fiber optic module to have a height-directional dimension of about
9 mm-25.4 mm.
Under such conditions as mentioned above, the aspect of the present
invention shown in FIG. 2 realizes a very small-sized module of
25.4 mm wide, 50.8 mm long and 11.5 mm high. When functions
necessary as the fiber optic module are sufficiently built into the
compact outline dimensions, it goes without saying that the
flexibility of mother board design by system manufacturers can be
remarkably expanded.
FIGS. 3 and 4 collectively show exploded perspective views of a
fiber optic module in accordance with a third aspect of the present
invention. In FIGS. 3 and 4, a laser diode module (which will be
referred to as the LD module, hereinafter) 50 for emitting an
optical signal and a photodiode module (which will be referred to
as the PD module, hereinafter) 40 for receiving an optical signal
are mounted onto a printed circuit board (which will be referred to
as the PCB, hereinafter) 30, to which a PD shielding plate 41 and
an LD shielding plate 51 are attached for the purpose of avoiding
electromagnetic or electrostatic noise. Also attached to the PCB 30
are a PCB connector 32 for establishing electric connection with a
mother board 60, an LD driver 33 formed as a semiconductor IC for
driving the LD module 50, and variable resistors 34 for adjusting a
current for driving of the LD module 50 or for adjusting the
detection level of a signal received at the PD module 40. For the
purpose of effectively making use of the mounting surface of the
PCB 30, a surface mounting type of PCB connector 32 is employed and
the variable resistors 34 are mounted onto the rear side of the PCB
connector 32. Since the surface mounting type of the PCB connector
32 is used in the fiber optic module of the present invention, the
need for the step for manually soldering a connector, which has
been necessary in the prior art, can be eliminated with the result
of realization of low-cost fiber optic module based on automatic
mounting. Further, the rear side of the PCB connector 32 may be
mounted with not only the variable resistors 34 but also chip
resistors or capacitors or such circuit parts as semiconductor ICs,
thus realizing a compact PCB 30.
In addition, since the variable resistors 34 are disposed on the
upper side of the PCB 30, the adjustment step during assembly of
the fiber optic module can be facilitated. In other words, since
the PCB connector 32 of the PCB 30 is mounted to a jig substrate of
the PCB 30 for assembly/adjustment of the fiber optic module, so
that, when compared with such a case that the variable resistors 34
are disposed on the same side as the PCB connector 32, the case of
mounting the variable resistors 34 on the upper side of the PCB 30
can be made high in the efficiency of adjusting works of the fiber
optic module by a worker. Thus, the more efficient adjusting works
lead to realization of a low-cost fiber optic module.
Each of PD and LD leads 47 and 57 has a relatively large land (not
shown) on its PCB connector 32 side to improve its assembling
efficiency to the PCB 30. Meanwhile, the mother board 60 also has a
mother connector 62 to be associated with the PCB 30.
The PCB 30 mounted with the PD module 40, LD module 50 and so on is
temporarily fixed by means of a snap-fit mechanism based on a
projection 12 of the upper frame 10 and a recess 22 of the lower
frame 20, so that a resultant assembly including these upper and
lower frames 10 and 20 and the PCB 30 forms a fiber optic module.
The PD and LD modules 40 and 50 mounted on the PCB 30 are fixed to
the upper and lower frames 10 and 20 through PD and LD shielding
plates 41 and 51 made of plate springs. Further, the PD and LD
shielding plates 41 and 51 are fixedly mounted to the PCB 30 by
soldering or by other means and surrounded by the lower frame 20,
so that the PD and LD shielding plates 41 and 51 can be secured
with very high mechanical stability. Since the shielding plates 41
and 51 are electrically isolated from the mother board 60 by the
lower frame 20, any short-circuiting and leakage of the plates with
respect to parts mounted on the mother board 60 can be avoided,
thus realizing a reliable fiber optic module.
The lower frame 20 is provided with pawls 23 for coupling the
optical signal with other fiber optic modules, so that the pawls 23
can snugly engage with optical fiber plugs (not shown).
After the temporarily fixed fiber optic module is positioned at its
rough position on the mother board 60 by fitting the PCB connector
32 into the mother connector 62, the fiber optic module is
completely fixedly mounted onto the mother board 60 by means of
tapping screws 70. More specifically, the tapping screws 70 are
passed through mother openings 61 provided in the mother board 60,
lower frame openings 21 and PCB connector 32, and then tightly
tightened into upper frame openings 11, whereby the fiber optic
module is completely fixed onto the mother board 60.
In general, reduction in the positioning accuracy between the
mother connector 62 and PCB connector 32 lead to the fact that a
load is imposed on the respective leads (PD leads 47 and LD leads
57) of the PD module 40 and LD module 50. In other words, although
the respective leads of the PD module 40 and LD module 50 are fixed
onto the PCB 30 by soldering or the like, since the PCB connector
32 is also fixed onto the PCB 30 by soldering or the like. For this
reason, if the positioning accuracy of the mother connector 62 with
respect to the mother openings 61 and the positioning accuracy of
the PCB connector 32 with respect to PCB openings 31 are not
improved, then these positioning errors result in loads imposed on
the respective leads of the LD module 50 and on lands (not shown)
of the PCB 30. More in detail, when the mother connector 62 is
mounted inaccurately apart from the mother openings 61 at the time
of building the fiber optic module into the mother board 60,
tensile stresses are imposed on the PD and LD leads 47 and 57 and
the lands of the PCB 30; whereas, when the mother connector 62 is
conversely mounted inaccurately close to the mother openings 61,
compression stresses are imposed on the PD and LD leads 47 and 57
and the lands of the PCB 30. These stresses result in the fact that
the reliability of the fiber optic module is remarkably reduced.
For the purpose of avoiding these tensile and compression stresses,
it is necessary to improve the positioning accuracy of the
connector part, which undesirably involves an increase in the cost
of the fiber optic module. It goes without saying that the similar
detrimental effect takes place even for the PCB connector 32.
However, in accordance with a third aspect of the present
invention, in which the mother openings 61, lower frame openings 21
and PCB openings 31 are set to have a diameter of 3.2 mm and the
upper frame openings 11 are set to have a diameter of 2.2 mm and
further the fixation of the fiber optic module is effected by means
of the employment of the tapping screws 70 (having a diameter of
about 2.6 mm), requirement of the positioning accuracy of the
mother connector 62 with respect to the mother openings 61 and the
positioning accuracy of the PCB connector 32 with respect to the
PCB openings 31 can be reduced so that loads caused by the tensile
and compression stresses imposed on the leads (47 and 57) of the PD
and LD modules 40 and 50 and on the lands of the PCB 30, which has
been a big problem in the prior art, are eliminated, thus realizing
a reliable fiber optic module. Further, since the requirement of
parts positioning accuracy can be radically reduced compared to the
prior art, not only the production management of assembly of the
PCB connector 32 for the PCB 30 can be facilitated but the required
accuracy of parts used in the PCB 30 and PCB connector 32 can also
be reduced, whereby a very inexpensive fiber optic module can be
realized.
The aforementioned numeric values for the upper frame openings 11,
lower frame openings 21, etc. are given as an example and thus the
present invention is not limited to the specific values. With the
arrangement of the third aspect of the present invention, it will
be noted that values other than the above numeric values may be
employed with substantially the same effects as the above.
In this way, when the fiber optic module is made compact and small
in size and is provided with indispensable minimum functions, the
system manufacturer can also design the mother board highly
flexible. That is, since the fiber optic module of the present
invention is made compact with its small occupation area to the
mother board and the fixation of the fiber optic module requires
only 3 small holes, the mother board can be designed highly
flexible.
In addition to the above, the arrangement of the 3 openings (upper
and lower frame openings 11 and 21 and mother openings 61) forms
such an isosceles triangle that stress loads caused by mounting and
dismounting of the fiber optic module are ideally dispersed, with
the result of implementation of a fiber optic module having a high
reliability.
Shown in FIG. 5 is a cross-sectional view of a major part of a
fiber optic module in accordance with a fourth aspect of the
present invention. In the drawing, the fiber optic module
comprising a PCB 30 and upper and lower frames 10 and 20 is secured
together with a mother board 60 by means of tapping screws 70 which
pass through mother openings 61 and lower frame openings 21 into
upper frame openings 11 and then fixed thereto. Electrical
connection between the fiber optic module and mother board 60 is
established by means of a PCB connector 32 and a mother connector
62.
The upper and lower frame openings 11 and 21 may also be used as
reference holes for parts acceptance test of the upper and lower
frames 10 and 20 respectively. Since the 3 upper frame openings 11
and the 3 lower frame openings 21 are set to have a drawing tape of
0 degree at their molding time, the accuracy of the respective
openings (upper and lower frame openings 11 and 21) can be
maintained high. Since the accuracy of the openings an be kept
high, when jigs designed for the parts acceptance test associated
with the openings are prepared, the parts inspection can be
facilitated. In other words, the upper and lower frame openings 11
and 21 can be used not only as holes for fixation of the fiber
optic module to the mother board 60 but also as parts inspection
holes.
Further, the fiber optic module of the present invention is
arranged so that loads imposed on the fiber optic module caused by
the mounting and dismounting of the optical fiber plug are
supported by the 3 tapping screws 70. More specifically, the
specification of the Japanese Industrial Standards JIS of the fiber
optic module prescribes 90N (newtons) with respect to the force
derived by mounting and dismounting of the optical fiber plug, so
that, for the purpose of satisfying this specification, it is
desirable that the tapping screws 70 have a diameter of 1.3 mm or
more. Further, from the viewpoint of safety design, the tapping
screws 70 are set to have a diameter of more desirably 2 mm or
more. In the fiber optic module of the present invention, since the
tapping screws 70 are set to have a diameter of 2.6 mm, there is
realized a reliable fiber optic module having a safety factor of 3
or more.
Although the fixation of the mother board 60 has been attained with
use of the tapping screws 70 in the fourth aspect of the present
invention, insert nuts (not shown) may be mounted in the upper
frame openings 11 and the tapping screws 70 may be replaced by
ordinary small screws (such as small crosshead screws and small
slotted screws) or the like with substantially the same effects as
the present invention.
When the fiber optic module has such an arrangement as shown in the
fourth aspect of FIG. 5 in this way, it is clear that there can be
avoided not only breakage of the resin frame legs but also the
improper electrical connection of the leads, which has been
problems in the prior art.
FIG. 23 is a block diagram of the fiber optic module of the
fourteenth aspect of the invention. The differences of the fiber
optic module in FIG. 23 compared with that of FIG. 1 are to be
added with serial to parallel converter 36 made of a semiconductor
integrated circuit IC for converting serial data 93 to parallel
data 95 and parallel to serial converter 37 made of a semiconductor
IC for converting parallel data 96 to serial data 94 and to be
replaced PCB connector 32 with PCB connector 38.
Describing in more detail, parallel data 96 transmitted from the
mother board are transferred to parallel to serial converter 37 via
PCB connector 38 on PCB 30 to be converted to serial data. On the
contrary, serial data 93 converted from the optical data are
converted to parallel data 95 by serial to parallel converter 36
and then transferred to the mother board. PCB connector 38 of the
aspect is different from PCB connector 32 previously described and
shown in FIG. 1, because the data transmitted with the mother board
through are parallel type which is different from the data shown in
FIG. 1. In concrete, the number of connecting pins of PCB connector
38 is larger than that of PCB connector 32 in FIG. 1.
FIG. 6 shows a cross-sectional view of a major part of a fiber
optic module in accordance with a fifth aspect of the present
invention. The present aspect is arranged so that a PCB 30 is
temporarily fixed by upper and lower frames 10 and 20 by means of a
snap-fit mechanism as already explained in connection with the
third aspect of FIG. 3, but is different from the aspect of FIG. 3
in that the rear part of the PCB 30 is also lightly depressed under
the influence of elastic deformation of an arm 14 of the upper
frame 10 in FIG. 6. In more detail, a step difference
(exaggeratedly shown in the drawing for clear illustration) of
about 0.2 mm is provided in upper frame openings 11 in the vicinity
of a contact surface between the upper frame openings 11 on the arm
14 and the PCB 30. When such an arrangement is employed, handling
of the fiber optic module in its temporarily fixed state becomes
more easily. In other words, since not only the front part of the
PCB 30 is held by the snap-fit mechanism but the rear part of the
PCB 30 is also held by the arm 14 of the lower frame 20, a stabler
fiber optic module assembly can be realized, so that not only
mounting of the fiber optic module to the mother board 60 but also
the handling of the fiber optic module per se can be
facilitated.
The prior art PCB is arranged so that the rearmost and frontmost
ends of the PCB are depressed by frames, thus causing a warpage
problem. On the other hand, since the PCB 30 in accordance with the
fifth aspect of the present invention is arranged so that the PCB
30 is held at its foremost part and a part slightly displaced
rearward from its center part, such a warpage problem as in the
prior art can be solved. Further, though the prior art arrangement
requires special strokes (length) for the PCB and the upper and
lower frames, the arrangement of the present aspect can eliminate
the need for such strokes and thus the fiber optic module of the
invention can easily be made small in size.
There is shown in FIG. 7 a perspective view of a modification of
the lower frame 20 usable in a fiber optic module in accordance
with a sixth aspect of the present invention.
In the sixth aspect of the present invention, the upper and lower
frames 10 and 20 are made of polybutylene terphthalate (PBT) mixed
with 10-30% of glass, with the result that the frames are excellent
in durability. In particular, the material of the frames improves
the durability of pawls 23 of a lower frame 20 for mounting and
dismounting of an optical fiber plug. Further, in order to reduce
forces imposed on the pawls 23 of the lower
frame 20, upper frame projection 16 (not shown: refer to FIG. 5)
are provided in an upper frame 10 (not shown: refer to FIG. 5) to
abut against associated lower frame projections 26 disposed at
roots of the pawls 23. The lower frame 20 subjected to a large load
caused by the mounting and dismounting of an optical fiber plug is
provided with a bottom plate 25 and a rib 24 in order to increase
the overall rigidity of the lower frame 20.
Although the frames have been made of PBT material in the sixth
aspect of the present invention, the present invention is not
limited to the above specific example but other suitable materials
may be employed as necessary.
Referring to FIG. 8, there is shown a plan view of a major part of
a fiber optic module in accordance with a seventh aspect of the
present invention, in which, for more detailed explanation, a lower
frame 20, a PCB 30 and LD module 50 and PD module 40 are
illustrated in plan view and partly in section. In case of a
general fiber optic module, it is predominant practice that a
spacing between the PD module 40 and LD module 50 is set to be 12.7
mm and the diameter of the PD element 45 and LD element 55 is to be
5 mm or so. For the purpose of protecting these PD and LD elements
45 and 55 and mechanically coupling these elements with the
associated optical fibers, it is necessary for the PD and LD
modules 40 and 50 to have a diameter of about 6 mm-8 mm.
Accordingly, a design limit for the diameter of a lower frame
opening 21 become about 4.7 mm-6.7 mm. In this case, when the
average wall thickness of the lower frame 20 is 1.5 mm, the
diameter of the lower frame opening 21 becomes about 1.7 mm-3.7
mm.
The optical fiber plug is mechanically mounted and dismounted to
and from the fiber optic module by utilizing pawls 23 of the lower
frame 20. The fiber optic module of the present invention has upper
frame openings 21 in the vicinity of the pawls 23 subjected to the
highest load during the above mounting and dismounting operation.
In this case, the diameter of the upper frame openings 21 is set to
be about 3 mm in order to ensure 1.5 mm of the average wall
thickness of the lower frame 20. Since the fiber optic module of
the present invention is highly downsized over the prior art fiber
optic module, the provision of the openings for fixation of the
fiber optic module disposed at the center part of the lower frame
20 and in the vicinity of the pawls 23 creates great effect of
realizing a reliable fiber optic module. In the seventh aspect of
the present invention, the lower frame openings 21 having a
diameter of 3 mm are provided in the lower frame at positions about
2.5 mm apart from associated lower frame projections 26 subjected
to the highest stress applied to the pawls 23, so that the rigid
lower frame 20 having an average wall thickness of 1.5 mm is
realized and therefore a highly reliable fiber optic module is
implemented.
Shown in FIG. 9 is a cross-sectional view of a major part of a
fiber optic module in accordance with an eighth aspect of the
present invention, that is, an assembled state of only the upper
frame 10 and the lower frame 20 for easy explanation. The upper
frame 10 is provided with a thin wall part 17 to prevent surface
scars generated by the non-uniform wall thickness of the upper
frame 10. More in detail, the thin wall part 17 prevents reduction
in the accuracy of upper shielding fit 17a for engagement with a PD
shielding plate 41 and in the accuracy of an upper module fit 17b
for engagement with an LD module both caused by such surface scars.
With regard to the lower frame 20, similarly, a thin wall part 27
is provided in the lower frame to prevent deformation of a lower
shielding fit 27a and a lower module fit 27b both caused by surface
scars similar to the mentioned above. In the eighth aspect of the
present invention, provision of these thin wall parts enables
achievement of the upper and lower frames 10 and 20 both having an
average wall thickness of 1.5 mm and thus realization of the highly
realiable upper and lower frames.
FIG. 10 is a cross-sectional view of a fiber optic module in
accordance with a ninth aspect of the present invention. The
present aspect is different from the foregoing fourth aspect of
FIG. 5 in that the tapping screws 70 are not used and pins 71 are
instead integrally fixed to the lower frame 20 by integral molding
(or press fitting) and the fiber optic module is fixedly mounted
onto a mother board 60 by means of nuts 72 engaging with the pins
71. For allowing the upper frame 10 and PCB 30 to be located at
rough positions, the upper parts of the pin 71 are projected
upwardly beyond the contact surface between the upper and lower
frames 10 and 20. Further, the pins 71 are also extended downwardly
through the mother board 60 to allow rough positioning of the fiber
optic module as guiding pins for automatic assembling. Furthermore,
in order to increase the rigidity of the fiber optic module, a rib
24 is extended toward the mother board 60.
In this way, even the arrangement of the fiber optic module shown
in FIG. 10 can not only remove the loads imposed on the respective
leads of the PD and LD modules 40 and 50 and on the lands of the
PCB 30 as already explained earlier in connection with FIG. 5 but
also reduce the mounting positional accuracy requirement of parts
such as connectors and the dimensional accuracy requirement of the
parts per se, whereby there can be realized a fiber optic module
with a high reliability and low cost. Further, the pins 71
integrally formed with the lower frame 20 may be used also as
reference positions for part acceptance test of the lower frame 20.
Furthermore, the LD shielding plate 51 and the PD shielding plate
41 shown earlier in FIG. 3 may be integrally formed with the lower
frame 20 together with the pins 71 to realize a fiber optic module
with a further reduced cost.
Of course, the fourth aspect of FIG. 5 may be combined with the
ninth aspect of FIG. 10 with substantially the same effects of the
present invention.
Although the 3 pins 71 (or tapping screws 70) have been used in the
ninth aspect of the invention (or in fourth aspect), only one pin
71 (or tapping screw 70) may be employed for the opening in the
vicinity of the pawls 23 imposed with the highest stress load due
to the mounting or dismounting of the optical fiber plug and resin
projections extended from the lower frame may be utilized for the
other openings in the vicinity of the arm 14, with substantially
the same effects of the invention.
FIG. 11 is a perspective view of a fiber optic module (or a
combination of upper and lower frames 10 and 20 and a PCB 30) in
accordance with a tenth aspect of the present invention, which
module is mounted with a cover 18 for prevention of electrostatic
destruction. After the fiber optic module is assembled and
adjusted, the cover 18 is mounted on the fiber optic module. Since
most of the mounted parts of the PCB 30 are covered with the upper
and lower frames 10 and 20 and the cover 18, the possible
electrostatic destruction of the fiber optic module during handling
thereof, which has been a problem in the prior art, can be
substantially avoided.
The material of the cover 18 is not specifically restricted by the
presence or absence of electrical conductive property of the
material. In other words, the material of the cover is not limited
from the viewpoint of resistance of the PCB 30 to the electrostatic
destruction and metallic and resin material can be employed. More
specifically, though the cover 18 has been made of the same PBT as
the upper frame in the present aspect, the electrostatic
destruction of the PCB 30 possible caused during handling of the
fiber optic module, which has been a problem in the prior art, can
be eliminated.
Further, even when the cover 18 is made of iron alloy from the
viewpoint of the electrostatic destruction resistance of the PCB 30
and the electromagnetic shielding of the PD module 40,
substantially the same effects can be achieved. It will be noted
that, even when the cover 18 is made of not only iron alloy but
also iron, aluminum, aluminum alloy, copper, copper alloy or the
like, substantially the same effects can be obtained. It will also
be appreciated that a method for fixing the cover 18 to the fiber
optic module may be the fitting method based on the arm 14, the
snap-fit method or bonding but the invention is not restricted to
the specific example.
In the fiber optic module of the present invention, next, the upper
surface of the upper frame 10 is made flat and the bottom plate of
the lower frame 20 is made also flat in order to increase the
rigidity of the lower frame 20, so that an identification label 90
indicative of the place of production of the fiber optic module and
a certification label 91 indicative of satisfied specifications of
laser safety standard can be easily pasted or bonded on the flat
surface of the upper or lower frame.
Further the flat part (not shown) of the upper frame 10 and the
flat part or a recess (not shown) of the lower frame 20 are
provided respectively with a step difference part or a recess (not
shown) of about 0.3 mm to allow easy bonding work of the
identification label 90 or certification label 91.
It goes without saying that, for the purpose of decreasing the cost
of the fiber optic module of the invention, not only these label
indications may be adhesive bonded as labels but may also be marked
in the respective frames.
FIG. 12 is a plan view of a fiber optic module in accordance with
an eleventh aspect of the present invention. The present aspect is
different from the tenth aspect of FIG. 11 in that a cover part 18a
is integrally formed with the upper frame 10. Another difference of
the aspects of FIGS. 11 and 12 from the other aspects is that a
cover opening 19 is provided in a cover part 18a so that, even
after the assembling of the fiber optic module is completed,
variable resistors on the PCB 30 can be adjusted through the cover
opening 19. Since the cover part 18a is formed integrally with the
upper frame 10 during molding thereof or is molded therewith at the
same time in this way, there can be implemented a fiber optic
module which is highly reliable and more economical. It will be
noted that, even when the cover opening 19 shown in the eleventh
aspect of the invention is applied to the tenth aspect of FIG. 11,
the effects of the present invention can be ensured.
Shown in FIG. 13A is an exploded perspective view of a fiber optic
module in accordance with a twelfth aspect of the present
invention, in which an supporting plate 73 is used for fixing the
fiber optic module to a mother PCB 60. The supporting plate 73 is
provided with a fixing part 74 so that, when the fixing part 74 is
rotated by an angle of about 90 degrees, the fixing part helps to
fix the fiber optic module. The fixation of the fiber optic module
is sufficient by means of the tapping screws 70 earlier given in
the fourth aspect (refer to FIG. 5) or the pins 71 in the ninth
aspect (refer to FIG. 10), but the additional use of the supporting
plate 73 enables provision of more reliable fiber optic module.
Further, when the supporting plate 73 is made of metallic material,
the supporting plate 73 can have functions of protecting the PD
module 40 from external electromagnetic noise and also of shielding
electromagnetic noise radiated from the LD module 50 onto external
elements. It will be appreciated that, although the supporting
plate 73 has been made of iron alloy in the twelfth aspect of the
present invention, iron, aluminum, aluminum alloy, gold, copper or
copper alloy may be employed as the material of the supporting
plate 73, with substantially the same or equivalent effects of the
invention. It will also be noted that, though the supporting plate
73 has been mounted from the top of the fiber optic module to help
to fix the fiber optic module to the mother board 60 in the twelfth
aspect of the invention, the supporting plate 73 may be mounted
from the bottom side of the mother board 60 to help to fix the
fiber optic module to the mother board 60, with substantially the
same effects of the invention.
FIG. 13B shows a perspective view of the assembled fiber optic
module of the twelfth aspect of the invention. As shown in FIG.
13B, the fiber optic module assembly including the PCB 30, the
upper frame 10, the lower frame 20 and other components is
assembled by being fastened to the mother board 60 first with the
tapping screws 70 and other fasteners as shown in FIG. 5 then being
mounted with the supporting plate 73 having fastening wings 74 at
the both ends. The fastening wings 74 are twisted at about 90
degrees to fix the fiber optic module assembly on the mother board
73.
Referring to FIG. 14, there is shown a perspective view of a fiber
optic module in accordance with a thirteenth aspect of the present
invention. A module cap 80 is attached to the fiber optic module
for preventing dust from invading into LD and PD modules in the
non-operative mode (during shelf-keeping, transportation, etc.) of
the present fiber optic module (i.e., an assembled combination of
upper and lower frames 10 and 20 and a PCB 30).
Next, the module cap 80 will be detailed in connection with FIG. 15
showing in plan view the fiber optic module of the thirteenth
aspect of the invention. For more detailed explanation of the
module cap 80, parts of the LD module 50 are shown in section. In
FIG. 15, and PD element 45 is fixed to a PD module 40 by bonding
(or welding) or the like and an LD element 55 is fixed to the LD
module 50 by welding (or bonding) or the like, so that the PD and
LD modules 40 and 50 are temporarily physically or mechanically
fixed to a lower frame 20 and electrically connected to the PCB 30
through PD and LD leads 47 and 57, respectively. The module cap 80,
which is arranged not to contact with pawls 23 of the lower frame
20, is provided with cap projections 85 for holding the module cap
80 to the fiber optic module and also with a handler 87 for easy
mounting and dismounting of the module cap 80 to and from the fiber
optic module. When the module cap 80 is mounted to the fiber optic
module, cap end surfaces 82 are not brought into contact with a
ferule abutment surface 56 of the LD module 50 and module abutment
surfaces 84 of the module cap 80 is brought into contact with an LD
module end surface 53 of the LD module 50, thereby preventing
invasion of dust into an LD module opening 52. Further, the
diameter of a cap projection 83 is designed to be sufficiently
smaller than the diameter of the LD module opening 52, so that the
module cap 80 can be easily mounted and dismounted while preventing
dust or foreign matter from generating in the opening 52 during the
mounting and dismounting of the module cap 80.
Shown in FIG. 16 is a perspective view of the fiber optic module in
accordance with the thirteenth aspect for clearer illustration of
the module cap 80. Elastic parts 86 ranging from the module
abutment surfaces 84 to the cap end surfaces 82 for preventing dust
from invading into the LD and PD modules 50 and 40 are elastically
deformed through the cap projections 85, so that the module cap 80
is held to the fiber optic module. The module cap 80 has a cap
opening 81 for parts acceptance test. For the material of the
module cap 80, relatively soft polyethylene is selected, but the
present invention is not limited to the specific example and any
material may be employed so long as the material is resin.
As has been explained in the foregoing, in accordance with the
present invention, when there is provided a compact fiber optic
module which is made to be 25.4 mm wide, 50.8 mm long and 11.5 mm
high and which is provided with indispensable minimum functions,
the fiber optic module can obtain the following features 1) to
6).
1) Since transfer of electric signals is carried out in the form of
serial data, the number of signal lines can be made as small as 22,
the configuration of the connector can be made small and further
the need for such semiconductor ICs for serial/parallel conversion
can be eliminated. Thus, not only the present invention can follow
a recent tendency of the rapid downsizing movement of host computer
but the design flexibility of mother board in system manufacturers
can also be remarkably expanded.
2) The fixation of the fiber optic module to the mother board in
the present invention is achieved by means of the tapping screws
passed through the respective openings and only 3 of small holes as
the openings of the mother board is sufficient. Therefore, the
design flexibility of the mother board for the system manufacturer
can be remarkably expanded. Further, since the fiber optic module
of the invention is structured so that force loads caused by the
mounting and dismounting of the optical fiber are all imposed on
the tapping screws, electrical lead connection failure can be
completely avoided and thus a highly reliable fiber optic module
can be realized.
In addition, since the invention is arranged so that the 3 openings
accommodate variations in the dimensional accuracies of parts,
stresses to
be applied to the leads of the respective modules can be removed
and it becomes unnecessary to increase the accuracies of the parts
and to manage the parts (such as parts acceptance test), thereby
realizing an inexpensive fiber optic module.
3) When the connector in the fiber optic module of the present
invention is of a surface mounting type, manual works including
direct connection of the signal line to the mother board by
soldering can be eliminated and thus the cost of the fiber optic
module can be made low.
4) When the printed circuit board is provided at its front side
with holding means for holding the circuit board by a snap-fit
mechanism of the upper and lower frames and at its rear side with
holding means for holding the circuit board by the upper frame
having a very weak elastic property, the circuit board can be
prevented from being warped and therefore can be made remarkably
high in reliability. Further, the need for the sufficient circuit
board holding length L, which has been necessary to be long enough
in the prior art, can be eliminated and thus a compact fiber optic
module can be implemented.
5) The circuit board is covered with the upper and lower frames
and/or the cover, therefore, worker's handling of the fiber optic
module for assembly or inspection can be facilitated, the
assembling and inspection efficiencies of the fiber optic module
can be enhanced, the fiber optic module can be manufactured
inexpensively with a high reliability while preventing the
electrostatic destruction of the circuit board.
6) When an inexpensive module cap having a simple shape is attached
to the fiber optic module, the cap can prevent dust from invading
into the fiber optic module during a long-term of shelf-keeping
time, any improper connection between the optical fiber and module
can be avoided, and thus the fiber optic module can be made
remarkably high in reliability.
In this way, the present invention has high practical effects.
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