Distributive communications network

Details Distributive communications network Distributive communications network

1995-04-21

1996-09-24

Boudreau, Leo

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

359118, 359121, H04J 1402

Patent

active

055596258

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a distributive communications network, and to a node therefor. The invention is particularly applicable to an optical fibre network.
2. Related Art
The existing `fixed access` networks, such as public switched telephone networks (PSTNs) and cable television networks, fall into two distinct topologies driven by different customer requirements. A PSTN has a `star` topology with a central node or exchange and a tiered access structure. It is designed for bi-directional real-time speech communications. Cable television networks have been developed to provide unidirectional (broadcast) services to customers. They have a `tree-and-branch` or switched star topology.
A known distributive communications network node has a first input path, and power divider means connected with the first input path and arranged to split incoming traffic on the first input path along a local output path and a wider area output path.
It has been recognized that it would be desirable to be able to provide an integrated broadband switched network for applications ranging from basic telephony through to data and high definition television signal transmission. One result of this recognition is the broadband integrated services digital network (B-ISDN). However, a significant factor, neglected by most B-ISDN studies, is the cost of implementing the necessary transmission and switching infrastructure for a national system.
Known optical broadband telecommunication networks utilize wavelength division multiplexing (WDM) techniques (see IEEE Communications Magazine, Vol. 29, No. 3, March 1989, pages 22 to 30, and Journal of Lightwave Technology, Vol. 9, No. 12, December 1991, pages 1702 to 1716).


SUMMARY OF THE INVENTION

The aim of the invention is to increase the amount of re-use of information transmission wavelengths within a network, while not incurring the disadvantage of multipath effects which can otherwise arise in wavelength re-use.
The present invention provides a distributive communications network comprising n access levels of nodes, each node comprising a first input path, power divider means connected with the first input path and arranged to split incoming traffic on the first input path along a local output path and a wider area output path, a second input path, and power coupler means arranged to combine traffic from the second input path with traffic on the local output path, wherein filter means are arranged in one or both output paths, the filter means being arranged to discriminate between relatively local area traffic in a first band of wavelengths (.lambda..sub.x) and wider area traffic in a second band of wavelengths (.SIGMA..lambda.-.lambda..sub.x), and to allow the local area traffic along the local output path and the wider area traffic along the wider area output path, and wherein each node has: or with the wider area output paths of associated nodes at a lower access level; with the second input paths of the associated lower access level nodes; and associated node at a higher access level, wavelength of which being used for communication with any other user terminal via an ith level node, where i=1 to n.
The invention also provides a node for incorporation in a distributive communications network as defined above, the node comprising a first input path, power divider means connected with the first input path and arranged to split incoming traffic on the first input path along a local output path and a wider area output path, a second input path, and power coupler means arranged to combine traffic from the second input path with traffic on the local output path, characterized by filter means in one or both output paths, the filter means being arranged to discriminate between relatively local area traffic in a first band of wavelengths (.lambda..sub.x) and wider area traffic in a second band of wavelengths (.SIGMA..lambda.-.lambda..sub.x), and to allow the local area traffic along the local output path and the wider area traffic alo

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Hill, "A Wavelength Approach to Optical Communications Networks", Proceedings, IEEE Conference on Computer Communications, 27-31 Mar. 1988, pp. 354-362, New Orleans US.
Wagner et al., "WDM Applications in Broadband Telecommunications Networks", IEEE Communications Magazine, Vol. 29, No. 3, Mar. 1989, Piscataway, NJ US.
Wailes et al., "Multiple Channel Architecture: a New Optical Interconnection Strategy for Massively Parallel Computers", Journal of Lightwave Technology, Vol. 9, No. 12, Dec. 1991, New York US.
Hill et al., "Evolutionary Wavelength Division Multiplexed Schemes for Broadband Networks", Technical Digest, 10th Optical Fiber Communication Conference, 19-22 Jan. 1987, p. 30, Reno US.
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