Patent Application
20070242691
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown.
While the apparatus for transferring optical data according to an exemplary embodiment of the present invention is applied to an optical burst switching system among optical switching systems, it is not limited to the optical burst switching system and may be easily applied to an optical packet switching system.
Referring to
According to an exemplary embodiment of the present invention, the optical switching system includes F input/output optical fibers 1 to F. At least one optical fiber may form a link to an adjacent optical switching system. Since the number of wavelengths λ1 to λL of each optical fiber is L and the number of input/output data channels I1 to IB and O1 to OB of the buffer module 600 capable of performing wavelength conversion and buffering is B, a total number of input channels of the optical switching system is F×L+B.
The demultiplexers 100a to 100n perform channel division to deliver a control packet and a data burst of an optical burst, which are multiplexed in a wavelength division multiplexing (WDM) scheme and transferred via input ports 10a to 10n from an external link, to different input channels, i.e., an input control channel Icc and an input data channel IDC.
The switching unit 200 is connected between the demultiplexers 100a to 100n and the multiplexers 300a to 300n via input/output data channels IDC and ODC, and performs a function of switching the input data channel IDC to the output data channel ODC according to control packet routing information from the control module 500 so that the data burst is transferred to a desired destination node.
The multiplexers 300a to 300n multiplex the output data channel ODC with an output control channel Occ in the WDM scheme at each output stage. The multiplexers 300a to 300n are connected to the external link via output ports 20a to 20n.
The switching control unit 400 controls switching operation of the switching unit 200 according to a predetermined control signal from the control module 500.
The control module 500 is connected between the demultiplexers 100a to 100n and the multiplexers 300a to 300n via the input/output control channels Icc and Occ, and performs general control of the optical switching system. The control module 500 receives a control packet from the input control channel Icc and obtains routing information required for transferring the data burst to the desired destination node.
Further, the control module 500 checks whether an output resource (e.g., wavelength) is available, and whether data bursts are in contention for the resource. According to the result of the determination of output resource availability, the control module 500 performs control to directly transfer the data burst via the available output resource, or outputs a predetermined control signal to the switching control unit 400 in order to deliver contending data bursts to the buffer module 600 and prevent their loss.
Specifically, the control module 500 determines whether the data bursts are in contention. When the data bursts are not in contention, i.e., when there is available destination output resource, the control module 500 immediately delivers the data burst to the available destination output resource to be delivered to the destination node.
When the data bursts are in contention, i.e., when a number of simultaneously input data bursts simultaneously attempt to occupy the same output resource, the control module 500 delivers the data bursts to the available buffer module 600 via available input data channels I1 to IB of the buffer module 600 in order to prevent loss of the data bursts.
The control module 500 includes a routing unit 510, a resource managing unit 520, a queuing unit 530, a control packet processing unit 540, and a burst scheduler 550, as shown in
The routing unit 510 determines a path via which a control packet input via the input control channel Icc is delivered, based on routing information in the control packet.
The resource managing unit 520 manages the output resource of the switching unit 200 and the input/output resource of the buffer module 600 and manages all operation states of the switching unit 200 and the buffer module 600.
The queuing unit 530 temporarily stores the control packet input via a receiving terminal Rx having a connection to the input control channel Icc until the control packet processor 540 is ready to process, while contention between the data bursts is being addressed.
The control packet processing unit 540 delivers the control packet, which is temporarily stored in the queuing unit 530, to a next destination node via the output control channel Occ having a connection to a transmitting terminal Tx, when the output resource is available.
The burst scheduler 550 outputs a predetermined control signal for controlling an output port, a wavelength, a transmission time or the like to the switching control unit 400 according to a predetermined control signal from the control packet processing unit 540, so that the data burst corresponding to the control packet is delivered without collision.
The buffer module 600 is generally controlled by the control module 500 and connected via the input/output data channels I1 to IB and O1 to OB assigned to the switching unit 200. When the data bursts contend with each other, the buffer module 600 receives the contending data bursts, converts them to electrical signals, buffers the electrical signals when the output resource is not available, and converts and delivers the electrical signals to available output resource (e.g., wavelength), under control of the control module 500.
The buffer module 600 includes an optical-electrical converting unit 610, a buffering unit 620, an electrical switch 630, an electrical switch controller 640, and an electrical-optical converting unit 650, as shown in
The optical-electrical converting unit 610 converts the data bursts, which are input via the input data channels I1 to IB of the buffer module 600, from optical signals to electrical signals.
The optical-electrical converting unit 610 includes a number of optical receivers, each connected to one of the input data channels I1 to IB of the buffer module 600.
In the optical-electrical converting unit 610, each optical receiver may be implemented by an element such as a photo detector capable of receiving all input wavelengths λ1 to λL in the optical switching system.
The buffering unit 620 is connected to an output of the optical-electrical converting unit 610 for receiving the data bursts converted to electrical signals from the optical-electrical converting unit 610 and temporarily storing the data bursts. Accordingly, the data bursts, which are converted to electrical signals, wait in the buffering unit 620 until the output resource is available.
Preferably, the buffering unit 620 is implemented by an electrical memory such as a random access memory (RAM), but it is not limited to an electrical memory. The buffering unit 620 may be implemented by an optical RAM or a future optical memory. Further, the buffer may have any depth.
The electrical switch 630 is connected between the output of the buffering unit 620 and the input of the electrical-optical converting unit 640, i.e., between the buffering unit 620 and the electrical-optical converting unit 640. The electrical switch 630 switches the data bursts stored in the buffering unit 620 to an available output laser diode of the buffer module 600 to be delivered to available output resource according to a predetermined driving control signal output from the electrical switch controller 640.
The electrical switch controller 640 controls a switching operation of the electrical switch 630 according to a predetermined control signal output from the control module 500.
The control module 500 checks whether the output resource, i.e., the output data channels O1 to OB of the buffer module 600 managed by the resource managing unit 520, is available, and outputs a predetermined control signal to the electrical switch controller 640 so that the data bursts stored in the buffering unit 620 are delivered to available output laser diode of the electrical-optical converting unit 650.
The electrical-optical converting unit 650 is connected between the output of the electrical switch 630 and the output data channels O1 to OB of the buffer module 600, and converts the data bursts input from the electrical switch 630 from electrical signals to optical signals corresponding to the available output resource.
The electrical-optical converting unit 650 may be implemented by a number of optical transmission laser diodes or any other type of optical source, each preferably connected to one of the output data channels O1 to OB of the buffer module 600.
Each laser diode or the optical source may be implemented by a variable or fixed wavelength laser diode or the optical source. When the laser diode is implemented by the fixed wavelength laser diode, the number of fixed wavelength laser diodes may correspond to the number of desired output resources (e.g., wavelengths).
Elements of this embodiment which are the same as in the embodiment shown in
In a buffer module 600 according to another embodiment of the present invention, the output of a buffering unit 620 is directly connected to an electrical-optical converting unit 650. The data bursts stored in the buffering unit 620 are converted and delivered to an available output resource within the output of the optical switching system through the electrical-optical converting unit 650 according to a predetermined control signal from the control module 500. The buffer module 600 can be implemented simply, easily, and at low cost compared to the embodiment of the present invention shown in
Referring to
When it is determined in step S100 that the data bursts are not in contention, the data bursts are switched to the available output resource without being converted to wavelengths or buffered, and delivered to an output port of a desired destination node (S110 and S120).
When it is determined in step S100 that the data bursts contend, the data bursts are delivered to the buffer module 600 of
When it is determined in step S140 that there are no available input data channels I1 to IB, the data bursts are lost (S150), and when there are available input data channel I1 to IB, the data bursts are buffered (S160).
In other words, the data bursts are converted from optical signals to electrical signals through the optical-electrical converting unit 610 of
It is then determined whether there is available output resource in the output of the optical switching system (S170). When there is available output resource, the data bursts stored in the buffering unit 620 are delivered to the electrical-optical converting unit 650 of
When it is determined in step S170 that there is no available output resource in the output of the optical switching system, the process returns to step S160 to continuously perform the buffering operation.
Referring to
Further, a scheme of preferentially transferring data bursts to the earliest available output wavelength was used as a scheduling method, and the buffer module 600 was based on a First In First Out scheme. However, the data bursts are first delivered to the earliest available output wavelength.
From the performance analysis performed under the above conditions, it can be seen that while the simple increase in the number of input/output data channels of the buffer module 600 does not significantly improve overall performance of the system, the use of the buffer module 600 according to an embodiment of the present invention (-▾- and -▪-) significantly improves system performance compared to the case having no buffer module 600 (--).
According to the apparatus and method for transferring optical data in an optical switching system of the present invention, when optical data input to a node are in contention, the optical data are converted from optical signals to electrical signals and temporarily stored. When the output resource is available, the stored optical data are converted to the available output resource and transmitted to a desired destination node. This enables going beyond intermittent buffering to achieve unlimited buffering when a conventional optical fiber delay line is used. Accordingly, an optical data loss rate can be reduced such that optical data can be efficiently transferred, and the apparatus can be implemented at low cost.
While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in from and detail may be made therein without departing from the scope of the present invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0033813 | Apr 2006 | KR | national |
