Optical communications – Multiplex – Optical switching
Reexamination Certificate
2001-02-05
2004-06-15
Chan, Jason (Department: 2633)
Optical communications
Multiplex
Optical switching
Reexamination Certificate
active
06751416
ABSTRACT:
TECHNICAL FIELD
This application relates to detection and recognition of bit information in digital data streams, and more specifically, to optical techniques and systems for detecting certain bit information such as headers in optical digital data streams.
BACKGROUND
Digital data may be transferred in communication networks in form of data packets. Each packet may include two separate parts. One part of the packet includes payload bits that carry the actual information or data. Another part of the packet includes header bits for data management such as addressing, sequencing, routing or other control information. Information or data from a signal source may be represented by a sequence of data packets.
A communication network may be designed to transfer information from a signal source to a destination by transferring the respective data packets individually in order to efficiently use the resources in the network. Hence, the data packets from the signal source may be transferred to their destination out of the sequence and through different physical signal links. Data packets from different signal sources thus may be mixed in a data stream directed from one node to another node. Each data packet is identified by its header. A switching device in such a network, e.g., a switch in a node, can direct each received data packet to one of the two or more desired output ports based on the header information.
The switching operation of the switching device is generally dictated by a switch look-up table that designates various header bit values to different switching operations. Hence, a header recognition mechanism may be needed to read and decode the header of an incoming data packet to generate a switch control signal according to the look-up table. The switch receives the switch control signal and performs the corresponding switch operation.
A portion or entirety of a communication network may be optical and hence is operable to transfer, manage, or process digital data superimposed on optical carriers. Optical wavelength-division multiplexing (WDM) allows transmission of multiple optical communication channels at different wavelengths through a single optical fiber for high-speed and broadband data communication applications. Various optical switches may be deployed in such a network to optically switch the data packets at switching speeds higher than many electronic switches. The header recognition mechanism for such an optical switch may also be implemented optically to provide high-speed optical header recognition.
SUMMARY
The optical header-recognition techniques and devices of the present disclosure are devised in part to recognize headers of data packets that have different bit rates less than or equal to a pre-selected maximum bit rate. An optical modulator may be used to simultaneously modulate two unmodulated, continuous-wave optical signals at two different wavelengths in response to signal modulations of an optical carrier signal that carry data packets with headers having at least a first bit and a second bit. The two modulated signals at the two different wavelengths carry the same data packets and synchronize with each other in time.
The two modulated signals may be directed into an optical delay unit that produces a time delay between light signals of the two different wavelengths. This time delay is set to be substantially equal to a pre-selected minimum bit length in time that corresponds to the pre-selected maximum bit rate so that the first bit of a header represented in one modulated signal at least partially overlaps with the second bit of the header represented in another modulated signal for each of said data packets.
A detection unit may be used to receive and detect the modulated signals with the relative time delay from the optical delay unit to determine whether values of the first and second bits in the header of each data packet respectively match a selected first bit value and a selected second bit value.
The optical header-recognition techniques and devices of the present disclosure may also provide a reconfigurable header recognition by adjusting the optical delay unit into different configurations for determining a match between bit values of a received header and different sets of selected bit values. In one embodiment, the optical delay unit may include two output optical terminals each operable to output either or both of the modulated signals with the time delay. The detection unit is configured so that different output assignments of the modulated signals to the two output optical terminals represent different sets of selected first and second bit values to be matched. The optical delay unit is operable to change from one output assignment of the modulated signals to the two output optical terminals to another output assignment in response to a control signal.
These and other embodiments and associated features are set forth in the accompanying drawings, the description, and the claims.
REFERENCES:
patent: 5581388 (1996-12-01), Gambini et al.
patent: 5617233 (1997-04-01), Boncek
patent: 6559989 (2003-05-01), Kim et al.
Cardakli Mustafa C.
Gurkan Deniz
Lee Sanggeon
Willner Alan E.
Chan Jason
Li Shi K.
University of Southern California
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