Nortel Networks Corporation

Canai Computer and Network Architecture Inc.

David Milton

Kexing Liu

Michel Pigeon

Gino Totti

Tomas Valis

David MacDonald Delaney

David P Schenkel

A communications network has a plurality of nodes interconnected by an optical transmission medium. The transmission medium is capable of a carrying a plurality of wavelengths organized into bands. A filter at each node for drops a band associated therewith and passively forwards other bands through the transmission medium. A device is provided at each node for adding a band to the transmission medium. Communication can be established directly between a pair of nodes in the network sharing a common band without the active intervention of any intervening node. This allows the network to be protocol independent. Also, the low losses incurred by the passive filters permit relatively long path lengths without optical amplification.

WDM optical network with passive pass-through at each node

Technique for detecting noise on a data channel

WDM optical network and switching node with pilot tone communications

A unidirectional bus data communication system which eliminates uncertainty as to the integrity of data received by a receiver connected to the bus, which data may have been involved in truncating collisions. A plurality of data stations are connected to a unidirectional bus which has segments connected to and between the stations. Each of the stations is connected to an upstream segment by a sense (S) lead and to a downstream segment by a transmit (T) lead. Each station is adapted to sense energy via its S lead arriving on an associated upstream segment of the bus and includes a transmitter for transmitting data signals via its T lead on an associated downstream segment of the bus. Signal delay elements interconnect upstream and downstream segments of the bus bypassing each of the stations. The time delay D of each of the signal delay elements is a function of the total interval of a predetermined group of data signal bit durations of the data signals added to a period T.sub.d which is equal to the time between arrival of energy at an S lead and the instant when an associated transmitting means can, in response to such detection, stop transmitting energy on its T lead.

System for implementing improved attempt-and-defer access contention

Growing community of inventors

Kanata, Canada

David Milton