Optical waveguides – With optical coupler – Plural
Reexamination Certificate
2002-03-29
2003-09-16
Patel, Tulsidas (Department: 2839)
Optical waveguides
With optical coupler
Plural
C385S031000, C385S130000
Reexamination Certificate
active
06621950
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates to a fixing board for fixing an optical data bus comprising a long plate of a light transmissive material having one side formed into a step-wise configuration and signal light incoming/outgoing areas formed by sloping each end surface of each step approximately at 45 degrees in relation to the plate surface, and relates to an optical back plane board using the fixing board.
(ii) Description of the Related Art
To improve the processing performance of a signal processing unit, which employs a parallel architecture comprising a back plane board (mother board) and a plurality of nodes (daughter board), enhancement of the bandwidth by increasing the speed of transmission through a bus and bit multiplication has been sought.
Although further speed increase is required for such a signal processing unit employing a parallel architecture, the achievement of further speed increases using a conventional electrical wiring requires a circuit board design for reducing noises and delay with respect to the mother board and the daughter board. Optical fiber interconnection also has been introduced for increasing speed, even though it leads to further complicated wiring.
While increasing speed of a signal processing unit by the conventional electrical wiring is sought, increasing speed of a signal processing unit by intra-system optical interconnection technology called optical interconnection has been considered. As the outline of optical interconnection technology is described, for example, in The Transactions of the Institute of Electronics, Information and Communication Engineers, Vol.79 (No.9), September, 1996, “Optical Interconnection Technology and its Applications” by Osamu WADA, pp.907-909 and in Journal of Japan Institute of Electronics Packaging, Vol. 1, No.3 (1998), “Toward New Computing Systems with Optical Interconnection” by Masatoshi ISHIKAWA, pp.176-179, various forms may be proposed depending on the configuration of a system.
However, when optical interconnection utilizing optical fibers as a signal transmission medium is introduced not only into systems for industrial use but also into systems commonly used in offices and homes, there are problems, such as high packaging cost due to need for accurate positioning of optical connections and difficulty in realizing interconnection of multiple nodes with a simple structure.
As technology to solve these problems, an optical data bus
50
as shown in
FIG. 6
was proposed at The 25th Symposium on Optics, 2000, Lecture No. 8, “Study on Backplane Optics and Apply to Optical Data Bus” by Junji OKADA et al.
The optical data bus
50
, which comprises a long plate of light transmissive material (for example, a light transmissive resin composed of an acrylic having a refractive index of 1.49 and an olefin polymer having a refractive index of 1.525, or the like), is a translucent transmission medium for transmitting signal light in the longitudinal direction by repetitive internal reflection.
Specifically, the optical data bus
50
comprises, as shown in
FIGS. 6A and 6B
, an approximately rectangular substrate of light transmissive resin having one longitudinal side thereof formed into a step-wise configuration, the steps being dimensioned such that light emitting elements (e.g. laser diode LD) or light receiving elements (e.g. photo diode PD) can be arranged from the side of one longitudinal end toward the other end. Signal light incoming/outgoing areas
52
are formed by sloping each longitudinal end of each of the steps at 45 degrees in relation to the surface of the substrate.
FIG. 6A
is a plan view of the optical data bus
50
and
FIG. 6B
is a side view thereof.
To perform optical transmission using the optical data bus
50
, a reflective diffusion portion (e.g. light diffusive film)
54
is provided on the end surface opposite to the signal light incoming/outgoing areas
52
of the optical data bus
50
so that the optical data bus
50
has the diffusion angle in the thickness direction of 0.2 degrees and the diffusion angle in the width direction of 40 degrees. In addition, a laser diode LD or a photo diode PD is disposed above each of the signal light incoming/outgoing areas
52
such that each optical axis intersects perpendicularly to the substrate surface of the optical data bus
50
.
Once the laser diode LD disposed above a given signal light incoming/outgoing area is activated and laser beam is irradiated from above the optical data bus
50
, the entering light is totally reflected from the end surface sloped at 45 degrees in relation to the substrate surface of the optical data bus
50
and transmitted toward the reflective diffusion portion
54
, then reflected and diffused from the reflective diffusion portion
54
. The reflected light, in turn, is totally reflected from the end surface of each signal light incoming/outgoing area
52
and emitted from the top surface of the optical data bus
50
. Thus, the optical signal emitted from the laser diode LD is transmitted to the photo diode PD disposed above the signal light incoming/outgoing area
52
, with the result that the signal transmitted through the laser diode LD and the optical data bus
50
can be obtained from the current flowing through the photo diode PD.
Therefore, if a back plane board including the above described optical data bus as a signal transmission medium is put into practical use, it is possible to achieve interconnection, with a simple configuration, of a plurality of circuit boards provided with at least one of light emitting means comprising an electronic circuit for generating an electrical signal and a light emitting element for converting the electrical signal to an optical signal, and light receiving means comprising a light receiving element for converting an optical signal to an electrical signal and an electronic circuit for processing the converted electrical signal.
The use of the above described optical data bus as a signal transmission medium, however, presents problems of how to fix the optical data bus. Specifically, it is required to relatively position the optical data bus, the light emitting element and the light receiving element such that light is totally reflected from the signal incoming/outgoing areas and an optical signal is transmitted by repetitive internal reflection through the optical data bus, which is a translucent transmission medium. Also, since optical transmission in the optical data bus utilizes the air having a refractive index of 1 as a cladding layer, it is preferable not to use an adhesive for fixing the optical data bus. Further, since the optical signal totally reflected from the signal light incoming/outgoing area is required to be reflected and diffused from the other end of the optical data bus, a reflective diffusion portion such as a light diffusion film needs to be provided to the optical data bus in an appropriate manner.
However, there has not been provided any appropriate fixing means in order to use, as a signal transmission medium, an optical data bus having a step-wise configuration, as shown in
FIGS. 6A
to
6
C. Therefore, an optical data bus fixing device which enables efficient transmission of an optical signal using an optical data bus is in demand.
The object of the present invention, which was meant to meet the demand, is to provide an optical data bus fixing board suitable for using the above described optical data bus as a signal transmission medium and an optical back plane board utilizing the optical data bus fixing board.
SUMMARY OF THE INVENTION
An optical data bus fixing board according to the present invention comprises a flat plate provided with a recess for insertion of an optical data bus opened corresponding to the surface configuration of the optical data bus and a positioning portion for positioning a light emitting element or a light receiving element in relation to each signal light incoming/outgoing area of the optical data bus inserted into the recess for insertion of an optical data
Higashiura Kenichi
Ito Shoji
Kato Makoto
Tanaka Akihiro
AICA Kogyo Co., Ltd.
Davis & Bujold P.L.L.C.
Patel Tulsidas
LandOfFree
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