Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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FIBER OPTIC DISTRIBUTION OF IMAGE DATA
BACKGROUND
The present invention relates generally to image data distribution systems,
and
more particularly, a high-speed fiber optic distribution system that may be
employed
with such image data distribution systems.
A data storage system known as a working storage unit manufactured by the
assignee of the present invention has input/output ports that are connected to
multiple
computer workstations and that are used for input and output of image data. A
straight-
forward conventional approach to the connection of the input/output ports to
multiple
workstations is complicated, requiring control actions that make the data
distribution
complicated. One such approach is to control data distribution through an RS-
232 link
from a host computer or from the working storage unit. When a command is sent
over
the RS-232 link, a connection to a workstation is established and data is
allowed to
flow to the workstation. This approach requires the RS-232 link and
controlling
software to send commands to control the data distribution. In addition the
data
distribution must have additional hardware to interpret and execute the
commands.
Furthermore, if the distribution system is complex, but is very fast, the data
distribution
cost per workstation is larger than the cost of the rest of the
workstation.
Therefore, it is an objective of an aspect of the present invention
to provide for data distribution apparatus that provides for relatively
fast distribution of large blocks of data, such as image data from a data
storage system to computer workstations coupled thereto.
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SUMMARY OF THE INVENTION
In order to achieve the above and other obj ectives, the present invention is
a
fiber optic distribution system for distributing image data using embedded
control
signals. The present distribution scheme is a very simple control technique
that pro-
vides for the distribution of image data over a fiber optic link.
The present invention provides for a data distribution system for use with a
data storage system, a host computer, and a plurality of computer workstations
(image
workstations), all of which are coupled together by way of a local area
network. The
host computer includes network software and associated files that provide
control in-
formation and functions for the distribution system, such as an image database
and
worklists associated with each of the computer workstations. The host computer
con-
trols access to the distribution system by setting up the data storage system
and the
computer workstations and controlling priorities regarding data transfer to
and from
the computer workstations. However, the host computer is not involved in the
actual
data transfer.
The data distribution system includes a distribution circuit that comprises a
high-speed logical switch that is capable of handling data transfer rates on
the order of
100 megabits per second. The distribution circuit is an electrical to optical
converter
which transforms electrical signals stored in the data storage system into
optical sig-
nals and vice versa. The distribution circuit is coupled to an input/output
port of the
data storage system but is not connected to the host computer or directly to
the com-
puter workstations. Optical signals provided by the distribution circuit are
carried by
an optical cable having a plurality of optical fibers. Each of the optical
fibers form a
bidirectional data link to a specified workstation. A first plurality of
optical interfaces
or couplers are optionally used to interconnect individual ones of the
plurality of opti-
cal fibers to individual fiber optic cables that are used to connect to the
computer
workstations. A second plurality of optical interfaces or couplers are
optionally em-
ployed at the other ends of each of the fiber optic cables to interconnect the
plurality
of fiber optic cables to the computer workstations. The second plurality of
optical in-
terfaces may be part of an interface card that is inserted into a card slot,
for example,
in the computer workstation that is coupled to the computer backplane. Such
card
slots are common in computer workstations such as most available personal
comput-
ers, for example, that are employed as workstations. The second plurality of
optical
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interfaces (or the interface cards) are also adapted to transform optical
signals into
electrical signals and vice versa.
Data is transferred between the data storage system and a selected one of the
plurality of computer workstations by transmitting a request from the selected
work-
s station to the host computer for use of the fiber optic cable connected to
the selected
workstation. When the input/output port is free and able to transmit to or
receive data
from that workstation, the host computer returns a message to the workstation
indi-
cating that the fiber optic cable coupled thereto may be used by the
workstation. The
host computer initializes the data storage system and input/output port and
sends in-
formation to the workstation as to the address locations of the image data.
The work-
station then sends a message along the fiber optic cable to the distribution
circuit
asking that the fiber optic cable be activated (such as by conventional
handshake sig-
nals). Once the fiber optic cable has been turned on, the workstation requests
transfer
of the data by means of a predetermined command. The addresses of the image
data
in the data storage system are retrieved from the host computer for use in the
request,
and the data storage system responds to the request by transfernng the data.
The im-
age data that is to be transferred is sent in one direction with
acknowledgements re-
turning to the source of the transmission to control the flow of the image
data. A
similar procedure is used in transferring data to the data storage system.
Both the data storage system and the interface contain appropriate
transmitters
and receivers that perform the data transmission and reception. The fiber
optic distri-
bution system provides data transmission rates on the order of 100 megabits
per sec-
and between the data storage system and the workstations.
According to another aspect of the present invention there is provided a data
distribution system for use with an image processing system comprising a data
storage
system having an input/output port, a host computer, and a plurality of
computer
workstations, a11 of which are coupled together by way of a network, and
wherein the
host computer comprises network software that is adapted to control
communication
of control signals between the data storage system and the plurality of
computer
workstations, said data distribution system comprising:
a distribution circuit coupled to the input/output port of the data storage
sys-
tem that is adapted to convert electrical signals derived from the data
storage system
into optical signals that are to be processed by the computer workstations and
for con-
verting received optical signals into electrical signals;
3a
A
a plurality of bidirectional interface circuits respectively coupled to the
com-
puter workstations for converting optical signals into electrical signals that
are
processable by the computer workstation and for converting electrical signals
into op-
tical signals that are transmittable to the distribution circuit; and a first
plurality of in-
dividual optical fibers respectively coupled between the distribution circuit
and the
plurality of computer workstations.
BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of the present invention may be more
readily understood with reference to the following detailed description taken
in con-
junction with the accompanying drawings, wherein like reference numerals
designate
like structural elements, and in which the sole figure of the drawing shows an
image
processing system employing a fiber optic distribution system in accordance
with the
principles of the present invention.
DETAILED DESCRIPTION
Refernng to the drawing figure, it shows an image processing system 10 em-
ploying an image data distribution system 20 in accordance with the principles
of the
present invention. The image processing system 10 is comprised of a data
storage
unit 11, also known as a working storage unit 11 manufactured by the assignee
of the
present invention, a host computer 12 and a plurality of computer workstations
13
comprising individual workstations 13a-13n that are each coupled to display
monitors
14a-14n that display the image data. The image data is typically
electronically stored
medical X-rays that are archived in the data storage system 11 and must be
quickly
distributed to a remotely located workstation 13. The image data is typically
a file
stored in a compressed format that is on the order of 5 megabits in size. The
data
storage unit 11 includes an input/output port 15 through which image data is
trans-
ferred. The data storage unit 11, host computer 12, and plurality of computer
work-
stations 13 are interconnected by way of a local area network 21, such as an
Ethernet
network, for example. The data storage unit 11 and each of the plurality of
computer
workstations 13a-13n are interconnected by way of the present image data
distribution
system 20.
The image data distribution system 20 is coupled to an input/output port 15 of
the data storage unit 11. The image data distribution system 20 comprised of a
distri-
bution circuit 16 that is coupled by way of a multi-fiber fiber optic cable
having a
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plurality of individual optical fibers 18a to a plurality of interface
circuits 17 (or cou-
plers). Each of the interface circuits 17 are individually coupled by way of a
single
fiber pair optic cable 18 to a second plurality of interface circuits 19
(couplers). The
interface circuit 19 may be an external circuit or an internal circuit
(forming part of an
interface card 19a) such as one described in U.S. Patent No. 5,315,424, issued
May
24, 1994, for "Computer Fiber Optic Interface", that is assigned to the
assignee of the
present invention.
With reference to the above-cited patent application, the interface circuit
19a
may comprise an optical receiver for receiving optical signals from the fiber
optic ca-
ble 18 and converting them into corresponding electrical signals for display
by the
workstation 13. An optical transmitter is provided for converting electrical
signals
derived from the computer workstation 13 into corresponding optical signals
and for
transmitting them to the data storage system 11. A plurality of data buffers
is pro-
vided for buffering the electrical signals received from the optical receiver
and to be
transmitted by the optical transmitter. A compression/expansion circuit is
optionally
provided for compressing and expanding the electrical signals generated by the
optical
transmitter or receiver, respectively. The compression/expansion circuit is
employed
to compress the image data file for storage in the data storage system 11 and
to ex-
pand a compressed image received from the data storage system 11. A data
buffer is
provided for buffering data signals received thereby. Backplane interface
circuit is
provided for interfacing between the data buffer and a computer bus or
backplane of
the computer workstation 13. The image data is coupled to the backplane and
from
thee to the display 14 in a conventional manner.
The fiber optic interface circuit 19a described in the above-cited patent
appli-
cation provides for direct fiber interface to the workstation 13. The
interface circuit
19a physically accepts the fiber optic cable 18 that carnes data signals to
and from the
data storage system 11 and couples the data onto the computer bus of the
workstation
13 at bus transfer rates. The fiber optic cables 18 employed in the
distribution system
20 are bidirectional. The fiber optic cable 18 is used to transfer
acknowledgement
signals to the data storage system 11 and distribution circuit 16. Data flow
can thus
be in either direction, in that images may flow to the workstation 13 for
display, or
from the workstation 13 to the data storage system 11 for storage.
The distribution circuit 16 is comprised of a logical switch that is capable
of
handling data transfer rates on the order of 100 megabits per second. The
distribution
circuit 16 is also an electrical to optical converter that transforms
electrical signals
5
into optical signals and vice versa. The distribution circuit 16 is coupled to
the in-
put/output port 15 of the data storage system but is not connected to the host
computer
12 or directly to the computer workstations 13.
The interface circuit 17 is optionally used to interconnect individual pairs
of
the plurality of optical fibers 18a to individual fiber pair optic cables 18
that are used
to connect to the computer workstations 13. The second fiber optic interface
19a is
optionally employed at the other end of each of the fiber optic cables 18 to
intercon-
nect each fiber optic cable 18 to a selected computer workstation 13. The
second fiber
optic interface 19a may be part of an interface card that is inserted into a
card slot in
the computer workstation 13 that is coupled to the computer backplane. Such
card
slots are common in computer workstations such as most available personal
comput-
ers, for example, that are employed as image workstations. The interface cards
19a
are also adapted to transform optical signals into electrical signals and vice
versa.
In operation, the image data distribution system 20 provides for distribution
of
image data from the data storage system 11 (working storage unit 11 ) to the
plurality
of computer workstations 13. The data storage system 11, the plurality of
computer
workstations 13, and the host computer 12 are coupled to the local area
network 21
and communicate thereacross. In transferring data from the data storage system
11 to
a workstation 13, the input/output port 15 of the data storage system 11
supplies data
to the distribution circuit 16. The distribution circuit 16 contains no direct
connection
to the host computer 12 or any other control system. The fiber optic cables 18
provide
a bidirectional data link between the data storage system 11 and the plurality
of com-
puter workstations 13. The image data that is to be transferred is sent in one
direction
(to or from the workstation 13) with acknowledgements returning to the source
of the
transmission (from or to the data storage system 11) to control the flow of
the image
data.
With reference to the drawing figure, the selection of the fiber optic cable
18
over which an image is distributed is made by reacting to a request
transmitted over
the fiber optic cable 18 from a particular workstation 13 after permission for
the re-
quest has
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been obtained from the host computer 12. Therefore, control of the flow of
data to and
from the data storage system 11 is controlled by means of messages sent from
the
workstations 13 to the host computer 12, and then from the host computer 12 to
the
data storage system 11, and vice versa.
Control of the channel formed by a particular fiber optic cable 18 is
exercised
from the workstation 13 coupled to that cable 18. In order to turn on the
fiber channel,
the workstation 13 requests access to the fiber optic cable 18 from the host
computer
12. When the port 15 is free and ready to transmit to or receive from that
workstation
13, the host computer 12 returns a message to the workstation 13 indicating
that the
fiber optic cable 18 coupled thereto may be used. The workstation I3 sends a
message
down the fiber optic cable 18 to the distribution circuit 16 asking that the
fiber optic
cable 18 be turned on. There is no competition for the port 15 , since the
workstation
I3 has alleviated the competition through its request for the use of the fiber
optic cable
18 from the host computer 12.
IS Once the fiber optic cable 18 has been tuned on, the workstation I3
requests
data from the data storage system 11 by means of an Ethernet command, for
example.
The image data address locations in the data storage system 11 are retrieved
by the
workstation 13 from the host computer 12 for use in the request. The data
storage
system 1 I responds by placing the data in an output buffer of the port 15 and
starts the
data flow.
The implementation of control of the image data distribution system 20 through
the fiber optic cable 18 makes the data distribution circuit 16 very simple.
There is no
computer in the data distribution circuit 16 to interpret commands from the
host
computer 12. The response to commands over the fiber optic cable 18 is a
hardware
response to a bit sequence that requests that a particular fiber optic cable
18 be
activated. Arbitration is done by interaction with the host computer 12 before
there is a
request for data from the data storage system 11. The result is a very
inexpensive
interface between the data storage system 1 I and the workstations I3. The
present
image data distribution system 20 is inexpensive enough that its cost per
workstation 13
is small compared to the cost of the workstation 13.
Thus there has been described a new and improved a image data distribution
system that may be employed with a image distribution system, workstations and
host
computer interconnected by way of a local area network. It is to be understood
that the
above-described embodiment is merely illustrative of some of the many specific
embod-
invents which represent applications of the principles of the present
invention. Clearly,
numerous and other arrangements can be readily devised by those skilled in the
art
without departing from the scope of the invention.
