Free space optical “backplane” (FSO)

Details Free space optical “backplane” (FSO) Free space optical “backplane” (FSO)

2001-04-26

2003-02-25

Feild, Lynn D. (Department: 2839)

Optical waveguides

Accessories

Reexamination Certificate

active

06526211

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to backplane system architecture, and more specifically to a free space optical backplane configuration.
BACKGROUND OF THE INVENTION
A communications system backplane provides a common bus having sockets through which switch cards and line cards may be connected to the other parts of the system. Typical wired backplanes use a particular type of architecture such as Asynchronous Transfer Mode (ATM), Internet Prototcol (IP), or other types of packet-based architecture. The drawback of such a scheme is that the particular bandwidth is set. Recent improvements in backplane architecture include the implementation of an optical backplane. An optical backplane has the advantage of providing much higher bandwidth capacity. An optical backplane can be implemented having scalable bandwidth and can take advantage of technologies such a dense wave division multiplexing (DWDM) to increase bandwidth and add flexibility to the system. Additionally, faster optical interfaces are being developed.
A disadvantage to typical optical backplanes is the amount of space they take up within the chassis.
FIG. 1
illustrates the configuration of two cards, within a chassis, optically connected according to the prior art. The system
100
shown in
FIG. 1
has two, for example, line cards
102
a
and
102
b
. Line cards
102
a
and
102
b
each have a laser transceiver
104
a
and
104
b
, respectively. Attached to laser transceiver
104
a
is a length of optical fiber known as a “pigtail”
106
a
. Pigtail
106
a
couples the laser transceiver
104
a
to a transition connector
108
a
that is coupled to a bulkhead
110
a
and likewise to another transition connector
112
a
. This interconnecting hardware takes up a great deal of space within the chassis. Transition connector
112
a
is connected to transition connector
112
b
via transmission fiber
114
. Transmission fiber
114
has a bend radius associated with it that is typically measured in inches. Transition connector
112
b
is coupled to bulkhead
110
b
and likewise to another transition connector
108
b
. Accommodating an optically interconnected backplane requires an excessive amount of the area of the card as well as the chassis. For example, the interconnecting hardware, together with the bend radius of the transmission fiber, requires from 2.5 to 3 inches of chassis space in a system typically having a 12-inch chassis.
SUMMARY OF THE INVENTION
A system allowing free-space optical data transmission is disclosed. The system is has a chassis having a plurality of card slots with at least one switch card having a plurality of switch card laser transmitters and a plurality of switch card photodetectors, inserted into a card slot. The system has at least one feature card having a feature card laser transmitter and a feature card photodetector, inserted into a card slot. The system has an alignment mechanism to align the at least one feature card such that the feature card laser transmitter aligns with a specified switch card photodetector and the feature card photodetector aligns with a specified switch card laser transmitter. The system also has a free-space optical data transmission path such that the feature card laser transmitter can transmit a signal to the specified switch card photodetector and the specified switch card laser transmitter can transmit a signal to the feature card photodetector.
Other features and advantages of the present invention will be apparent from the accompanying drawings, and from the detailed description, which follows below.


REFERENCES:
patent: 4121249 (1978-10-01), Lemelson
patent: 4288825 (1981-09-01), Hasuo et al.
patent: 4398223 (1983-08-01), Lamelson
patent: 4434510 (1984-02-01), Lamelson
patent: 4511930 (1985-04-01), Lemelson

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