Free space optical broadband access system

• US 6,650,451 B1
• Filed: 08/24/1999
• Issued: 11/18/2003
• Est. Priority Date: 01/19/1999
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Richardson, Robert E., Byers, Charles Calvin, Hinterlong, Stephen Joseph, Novotny, Robert Allen
• Primary Examiner(s): TWEEL JR, JOHN ALEXANDER
• Application Number:
  US09/379,649
• Time in Patent Office: 1,547 Days
• Field of Search: 359/159, 359/172, 359/152, 359/118, 359/125
• US Class Current: 398/129
• CPC Class Codes: H04B 10/1125 using a single common optical path

Abstract

The scanning free space optical broadband access network uses LASERs to carry high-speed data streams between a central location and a number of subscribers served from that location. High-speed digital data modulates the LASERs in both directions, allowing a virtual MAN to be created. A few dozen subscribers share a single virtual pipe with several hundred Mbps band-width available. Beam scanning techniques at a central hub permit a single LASER and optical assembly to serve many customers.

Claims

1. In a free space optical broadband access system apparatus for communicating between a source and a plurality of destinations, comprising:

means for steering a LASER beam at the source to each of said plurality of destinations;

means, coupled to said means for steering, for receiving a modulated LASER beam from each of said plurality of destinations;

means for receiving communication signals from, and transmitting communication signals to a communication network;

means, coupled to said means for steering, and said means for receiving communication signals from said communication network for modulating the steered LASER beam with the signals received from the network, toward each of said plurality of destinations; and

means, coupled to said means for transmitting communication signals to said network for demodulating the received LASER beam, thereby transmitting the received signals to the network;

wherein said means for steering comprises;

means for steering said transmitted modulated LASER beam to each active one of said plurality of destinations during a cycle;

wherein said cycle is limited to an acceptable upper limit of latency for data being exchanged between said apparatus for communicating, and each of said plurality of active destinations.

2. The apparatus of claim 1, further comprising apparatus in each of said plurality of destinations, said destination apparatus comprising:

LASER beam means, aimed at said apparatus for communicating with a plurality of destinations; and

receiving means, aimed to receive a LASER beam from said apparatus for communicating with a plurality of destinations;

means, for modulating said transmitted LASER beam with data from said destination; and

means, for demodulating said received LASER beam for transmitting data to said one destination.

3. The free space optical broadband access system of claim 1, wherein a plurality of the apparatus for communicating with a plurality of destinations are mounted on one tower, and each of said plurality of apparatus serves destinations within a sector of the area over which apparatus mounted on said tower can transmit.

4. The apparatus of claim 3, wherein more than one apparatus for communicating can communicate with destinations one sector via redundant paths.

5. The apparatus of claim 1, further comprising means, coupled to said means for steering, for compensating for deflections of said source.

6. The apparatus of claim 5, wherein said means for compensating comprises means for detecting high error rates in signals received at ones of said destinations.

7. The apparatus of claim 5, wherein said means for compensating for deflections comprise a plurality of receiving photo diodes, and means for measuring signal strength error rate on ones of said plurality of diodes for altering an angle of said LASER beam.

8. The apparatus of claim 5, wherein said means for compensating comprises means for detecting rapid changes in deflection of a tower for mounting said LASER beam.

9. The apparatus of claim 8, wherein said rapid deflections are caused by wind and sensed by acceleration gauging.

10. The apparatus of claim 5, wherein said means for compensating comprises means for detecting slow changes in deflection of a tower for mounting said LASER beam.

11. The apparatus of claim 10, wherein said slow deflections are caused by unequal heating of said tower and sensed by temperature sensors on all sides.

12. The apparatus of claim 1, further comprising an inter-source backbone/network for communicating among said means for receiving communication signals from, and transmitting communication signals to a communication network.

13. The free space optical broadband access system of claim 1 further comprising:

a plurality of destination units for receiving signals from said LASER beam of said source, and transmitting a modulated LASER beam to said means for receiving a modulated LASER beam.

14. The destination unit of claim 8, comprising an indoor segment for interfacing with customer premises equipment, and an outdoor segment for communicating with said apparatus for communicating between a source and a plurality of destinations.

15. The destination unit of claim 8, further comprising means for measuring error rates of received signals, and for communicating error rate information to said apparatus for communicating between a source and a plurality of destinations.

16. The apparatus of claim 8, further comprising optical filters to improve signal to noise ratio.

17. The apparatus of claim 8, further comprising filters to protect equipment from being destroyed by focused sunlight.

18. The apparatus of claim 8, wherein a wavelength of the LASER beam used for transmitting signals to a destination unit is different from a wavelength used for transmitting signals from a destination unit.

19. The apparatus of claim 1, further coming optical filters to improve signals to noise ratio.

20. The apparatus of claim 1, further comprising filters to protect equipment from being destroyed by focused sunlight.

21. The apparatus of claim 3, wherein each of the plurality of apparatus serving destinations within a sector can also serve destinations at fringes of adjacent sectors thereby providing means for balancing the load between units serving adjacent sectors.

22. The apparatus of claim 3, further comprising a second set of apparatus for covering all sectors of the area.

23. The apparatus of claim 22, wherein the sectors assigned to the second set are angularly displaced from the sectors for the first set of apparatus.

24. The apparatus of claim 23, wherein each sector covers a basic angle of 45 degrees, and wherein the second set of sectors are displaced by 22.5 degrees from the sectors for the first set.

25. The apparatus of claim 1, wherein data is simultaneously exchanged in both an upstream and downstream direction, and wherein the wavelength for upstream and downstream transmission is different.

26. The apparatus of claim 25, wherein each of the destinations that is active is served at least once in every pre-determined short period, and that inactive destinations are served at a slower rate under heavy load.

27. The apparatus of claim 1, wherein each of said destinations have battery backup for power;

wherein reliable power is provided for telephone users served by said apparatus.

28. The apparatus of claim 1, further comprising beam expanders to improve divergence and immunity to weather conditions, and to improve eye safety.

29. The apparatus of claim 1, wherein an upper limit of time is set for each active user destination for each cycle, and wherein, if no data is available to be transmitted from or to a particular active user destination prior to having reached said upper limit of time, transmission from and to a next active user destination is started.

30. The apparatus of claim 1, wherein each idle user destination is tested at least once per user activity cycle to see if said idle user destination has become active.

31. The apparatus of claim 30, wherein said user activity cycle is longer than said cycle for steering said transmitted modulated LASER beam.

32. The apparatus of claim 1, wherein during installation, an approximate deflection angle is calculated for the source by determining a user'"'"'s location using a GPS, (Global Positioning System), and calculating an angle from said user'"'"'s location and the source location.

33. In a free space optical broadband access system, apparatus for communicating between a source and a plurality of destinations, comprising:

means, for steering a LASER beam at the source to each of said plurality of destinations;

means, coupled to said means for steering, for receiving a modulated LASER beam from each of said plurality of destinations;

means for receiving communication signals from, and transmitting communication signals to a communication network;

means, coupled to said means for steering, and said means for receiving communication signals from said communication network for modulating the steered LASER beam with the signals received from the network, toward each of said plurality of destinations; and

means, coupled to said means for transmitting communication signal to said network for demodulating the received LASER beam, thereby transmitting the received signals to the network;

means, coupled to said means for steering, for compensating for deflections of said source;

wherein said means for compensating comprises means for detecting slow changes in deflection of a tower for mounting said LASER beam; and

wherein said slow deflections are caused by unequal heating of said tower and sensed by temperature sensors on all sides.