Optical communications – Multiplex – Broadcast and distribution system
Reexamination Certificate
2000-08-17
2004-09-07
Negash, Kinfe-Michael (Department: 2633)
Optical communications
Multiplex
Broadcast and distribution system
C398S083000, C398S115000, C398S118000, C379S056200
Reexamination Certificate
active
06788898
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a local access network that links nodes with a free space optical channel. In particular, the invention relates to a network that brings telephony and data services to the home without a need for wire or fiber to the home.
2. Description of Related Art
Free space optical transmission links are known and can provide broadband service potentially superior to that of radio wireless services. However, the free space optical transmission links are degraded in adverse environment conditions. It has been a challenge to offer continued service when high data rate optical links are unavailable.
SUMMARY OF THE INVENTION
Free space optical channels link together plural distributed switching nodes into a network. A central controller commands these nodes over a known radio telephone system to select alternative network routes to a destination that will bypass adverse environment conditions.
It is an object of the present invention to provide a network with broadband performance even in the presence of adverse link conditions such as rain or fog. It is a further object of the present invention to provide 911 services and critical low speed data services in the presence of adverse link conditions.
These and other objects are achieved in a communication system that includes a plurality of nodes and a plurality of point-to-point links that interconnect the plurality of nodes into a network. Each node includes an optical switch to controllably route a plurality of in-ports of the optical switch into a plurality of out-ports of the optical switch. Each point-to-point link includes a free space optical channel. A first free space optical channel couples to a first node through a receive path and through a transmit path. The receive path couples to a respective in-port of the optical switch of the first node, and the transmit path couples to a respective out-port of the optical switch of the first node.
These and other objects are achieved in an alternative embodiment of a communication hub that includes a plurality of neighborhood links to corresponding users, an optical switch coupled to the plurality of neighborhood links, and a trunk coupled between the optical switch and a free space optical channel link to the network.
These and other objects are achieved in a method of communicating in a network having plural links that includes sensing the presence of a received signal failure by monitoring channel losses in a first link, the received signal failure resulting from at least one of rain and fog. The method further includes sending data in a free space optical channel of the first link when the received signal failure is sensed due to rain and sending the data in an RF channel of the first link when the received signal failure is sensed due to fog.
REFERENCES:
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A. Acampora, S. Bloom, S. Krishnamurthy, “UniNet: A Hybrid Approach for Universal Broadband Access Using Small Radio Cells Interconnected by Free-Space Optical Links”, IEEE Journal on Selected Areas in Communications, vol. 16, No. 6, Aug. 1998.
Britz David M.
Dodley Jeevan Prakash
Lin Lih-Yuan
Miller Robert R.
AT&T Corp.
Negash Kinfe-Michael
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