At&t Bell Laboratories

Kristin F Kocan

Cyrus F Ault

George H Simmons

In a protection-switching arrangement, each optical output of replicated switching nodes (12,13) is connected to the input of an error detector (17,18) and of an optical delay line (19,20); their outputs are in turn connected to inputs of an optical AND gate (21,22). The error detector generates an error signal when it detects error in data at the connected output. The error signal causes the connected AND gate to block signals incoming from the connected delay line. The delay line is sized to ensure that the connected AND gate, when responding to an error signal, blocks signals whose error status is represented by that responded-to error signal. AND gates whose inputs are coupled to like outputs of the switching nodes have their outputs connected to inputs of an optical OR gate (23). The OR gate combines signals received at its inputs into a single signal at its output. The switching nodes may be replaced by computers, transmission lines, or other replicated signal-handling elements.

Protection against loss or corruption of data upon switchover of a

In a data communication network (100) wherein using units (104-111) contend for access to the network communication bus (160), data links (101-103) interface using units located remotely from the bus to the bus for communication such that the distances between the using units and the bus are rendered functionally transparent from the viewpoint of the bus. A data link (102) includes a network interface circuit (117) connected to and located near the using unit (108) for buffering communications passing between the using unit and the bus, a data transfer controller circuit (151) connected to and located near the bus for communicating on the bus on behalf of the using unit according to the communication protocol of the bus, a local fiber optic extension circuit (141) connected to and located near the data transfer controller circuit for emulating thereto the network interface circuit, a remote fiber optic extension circuit (125) connected to and located near the network interface circuit for emulating thereto the data transfer controller circuit, and an optical fiber link (131) connecting the fiber optic extension circuits.

Data link extension for data communication networks

A multipoint access data communication system which includes a communication bus, a plurality of transceivers connected to the bus for communication, and a remote collision detector associated with each transceiver for detecting collisions between communications on the medium, has improvements which adapt the transceivers for connection to a plurality of network interface units, and local access arbitrators associated with the transceivers for preventing collisions between transmissions simultaneously attempted by two or more network interface units connected to a transceiver.

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Chicago, IL, United States of America

Kristin F Kocan