Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-03-05
2001-11-27
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06323980
ABSTRACT:
The present invention relates to communication systems and in particular to free space optical communication systems.
BACKGROUND OF THE INVENTION
During the past several years, the telecommunication industry has enjoyed an explosive growth. The industry has strained to meet the demand. Global, national and regional telecommunication techniques primarily include: (1) telephone networks providing voice, data and FAX transmission using twisted wire, coaxial cable, fiber optics and microwave systems, RF networks; (2) television networks providing television through RF transmission, cable systems providing television through fiber optic and coaxial cable systems; and the internet communication system. Television, telephone and data communication is also currently being provided through satellite-based systems. Non-voice communication including high-speed data, image and video communication has provided a need for data rate communication much higher than that required for voice communication.
Radio communication permits the user to be mobile. It does not require expensive wiring connecting the communication equipment. The problem with radio communication is that the available radio bandwidth is limited. A solution to limited radio bandwidth is to create many separate geographical cells and to use an available bandwidth over and over again in very many of these separate cells. A large number of separate cells using the same bandwidth can increase greatly the number of users of a given bandwidth. The larger the number of cells, the larger the number of potential users. This is the theory behind the currently popular cellular telephone systems.
In the past telephone and cable systems have generally operated on a regulated monopoly basis. Currently, however, the federal, state and local governments in the United States are encouraging competition in the provision of these services. Local telephone and cable companies are reluctant or charge dearly to share their installed infrastructure and the installation of new cable or fiber optics is generally very expensive and disruptive. In many developing countries there is no significant wired communication infrastructure in place and installing a wired infrastructure would be expensive and disruptive. Certain events such as the Olympic Games and the Super Bowl create temporary need for greatly expanded communication in a region. Disasters such as major ice storms or hurricanes can disrupt existing communications creating a need for temporary communication equipment until the existing system can be repaired. Techniques for providing free space optical communications are known. (See “A Brief History of Free-Space Laser Communications” by David L. Begley in
Selected Papers on Free
-
Space Laser Communications
, David L. Begley, ed., SPIE Optical Engineering Press, 1991.) Free space laser communication has been proposed for satellite to satellite communication. This is because laser beams can provide high bandwidth long distance efficient communication above the earth's atmosphere. However, free space laser communication has generally not been seriously considered for wide spread terrestrial communication because of the perceived adverse effects of atmospheric condition such as rain, fog and snow.
What is needed is a local telecommunication system, which can be installed easily, efficiently and without significant disruption.
SUMMARY OF THE INVENTION
The present invention provides a free-space laser communication system. The system is comprised of a large number of picocells. Each picocell comprises a base station providing conventional communication with at least one user but typically several or many users. Each base station comprises at least two laser transceivers each transceiver having a pointing mechanism for automatic alignment. These transceivers provide communication with other base stations, relay information between other base stations or transmit information to conventional communication systems. The picocells cover relatively small geographical ranges such as about 100 meters. Applicant has demonstrated that at these distances atmospheric effects attenuating laser beams are not a serious problem. In a preferred embodiment the base stations generally comprise four laser transceivers with micro processor controlled pointing equipment which are aligned automatically to point at other base stations and an RF transceiver to provide communication with users.
The present invention is especially suited for providing a communication system which can be almost immediately installed to compete with established local monopoly (or near monopoly) telephone systems. Systems according to the present invention can be installed within a few hours or a very few days. These systems can provide, for a local area, its first communication system, or provide communication services in a local area in the event an existing local system is damaged such as in a natural disaster or provide a quick temporary expansion of existing communication capacity.
REFERENCES:
patent: 4730310 (1988-03-01), Acampora et al.
patent: 4789983 (1988-12-01), Acampora et al.
patent: 5264955 (1993-11-01), Sakanaka
patent: 5493436 (1996-02-01), Karasawa et al.
patent: 5710652 (1998-01-01), Bloom et al.
patent: 6049593 (2000-04-01), Acampora
patent: 0 859 478 A2 (1998-08-01), None
patent: 2 261 575 A (1993-05-01), None
patent: 98/32250 (1998-07-01), None
Wake et al., “Passive Picocell-A future integrated wireless communications network,” British Telecommunications Engineering 16:109-112 (1997).
Air Fiber, Inc.
Bello Agustin
Fish & Richardson P.C.
Pascal Leslie
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