Optical communications – Multiplex – Optical switching
Reexamination Certificate
2000-12-26
2004-09-07
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Optical switching
C398S053000, C398S054000
Reexamination Certificate
active
06788896
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to switches and, more particularly, to a technique for all-optical packet switching.
BACKGROUND OF THE INVENTION
In fiber optic technology, data may be transmitted through fiber optic cables in the form of light waves. Fiber optic cables are thinner and lighter then traditional metal communication cables, and have greater bandwidth then metal cables, allowing fiber optic cables to carry more data. Fiber optic cables also allow data to be transmitted in digital form rather than in analog form, making fiber optic cable more suitable for carrying computer data. Fiber optic cables are also less susceptible to interference than metal cables.
Thus, fiber optics has become a popular technology for network applications such as local area networks and communications network. Fiber optic networks may carry data in the form of optical data packets, and use switches to forward the optical data packets between networks segments.
Optical packets in fiber optic networks may include an optical packet header portion and an optical packet payload portion. In a typical optical packet switching system, the system may be required to “read” and “write” the optical packet header for each optical data packet electronically. Thus, the optical packet payload for each optical packet needs to be delayed until its associated packet header has been electronically processed.
In a multi protocol label switching (“MPLS”) switch network, a “shim” header is added to each internet protocol (“IP”) packet. The shim header is used as a “label”. Each MPLS switch may read and write this label and switch the IP packets based on the value of the label. The shim header may include at least two parts, a label and a time to live (“TTL”). The label part of the header is used for switching navigation purposes and the TTL portion of the header is used to avoid an infinite loop when the packet is being transmitted through a network. When the value of TTL drops to zero, the packet will be dropped from transmission in the network.
An optical to electrical conversion must be performed on the header at the switch, so that the header may be read. Then, an optical to electrical conversion must be performed on the header so that the header may be transmitted through the fiber optic network with the payload. The optical to electrical to optical conversion of the optical packet header during processing in a switch slows down switching speed and adds to system cost.
In view of the foregoing, it would be desirable to provide a technique for all-optical packet switching which overcomes the above-described inadequacies and shortcomings. More particularly, it would be desirable to provide a technique for all-optical packet switching in an efficient and cost effective manner.
SUMMARY OF THE INVENTION
According to the present invention, a technique for all-optical packet switching is provided. In one embodiment, the technique is realized by receiving at least one data packet over a network, disassociating a payload portion from a first header in the data packet, forming a second header based on a first information in the first header, associating the payload portion with the second header to form a modified packet and switching the modified packet based on a second information contained in the first header.
In accordance with other aspects of the present invention, the optical packet header may include a label. The label may include destination information that is pre-calculated before the optical packet is transmitted from its origin. The switching fabric of the switch may be controlled by the information contained in the label of the optical packet. The switch may further comprise a pre-configured signaling protocol to change the label of the optical packet header.
In accordance with further aspects of the present invention, the technique for switching includes an all-optical packet switching apparatus. The apparatus may include an optical pilot tone eraser, a photo diode, an electrical frequency detector, a switch controller, a modulation unit, at least one fiber delay and a network element.
The optical pilot tone eraser may be configured to receive at least one data packet and disassociate a header from a payload of the data packet. The photo diode may be coupled to receive the header of the data packet from the optical pilot tone eraser and convert the header to an electrical control signal. The electrical frequency detector may be coupled to receive an input from the photo diode.
The switch controller may be coupled to receive an input from the electrical frequency detector. The modulation unit may include a synthesizer which may be coupled to receive an input from the switch controller and output a modulated header signal. The at least one fiber delay may be coupled to receive the payload signal from the optical pilot tone eraser and output a delayed payload signal.
The network element may be coupled to receive inputs from the modulation unit, the fiber delay and the switch controller to associate the header to the payload to form a modified data packet, switch the modified data packet, and output the modified data packet to an optical network interface.
The present invention will now be described in more detail with reference to exemplary embodiments thereof as shown in the appended drawings. While the present invention is described below with reference to preferred embodiments, it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could be of significant utility.
REFERENCES:
patent: 5430715 (1995-07-01), Corbalis et al.
patent: 6032190 (2000-02-01), Bremer et al.
patent: 6519062 (2003-02-01), Yoo
patent: 6545781 (2003-04-01), Chang et al.
patent: 6657757 (2003-12-01), Chang et al.
“A Proof-of-Concept, Ultra-low Latency Optical Label Switching Testbed Demonstration for Next Generation Internet Networks,”by G.K. Chang et al., Proceedings of the Optical Communication Conference, Baltimore, Maryland, WDS, Mar. 2000, pp. 56-58.
“All-Optical Label Swapping with Wavelength Conversion for WDM-IP Networks with Subcarrier Multiplexed Addressing,”by D.J. Blumenthal et al., IEEE Photonics Technology Letters, vol. 11, No. 11, Nov. 1999.
Goodwill Dominic
Kim Ki-hong
Toliver Paul
Wang Guo-Qiang
Chan Jason
Hunton & Williams
Tran Dzung
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