Optical Wireless Communications Using Ultra Short Light Pulses and Pulse Shaping

• US 20070242955A1
• Filed: 06/01/2005
• Published: 10/18/2007
• Est. Priority Date: 06/01/2004
• Status: Abandoned Application

• Current Assignee: Penn State Research Foundation (Pennsylvania State University)
• Original Assignee: Penn State Research Foundation (Pennsylvania State University)
• Inventors: Kavehrad, Mohsen
• Application Number:
  US11/569,923
• Publication Number:
  US 20070242955A1
• Time in Patent Office: Days
• US Class Current: 398/130
• CPC Class Codes: H04B 10/1121 One-way transmission
• CPC Class Codes: H04B 10/1149 Arrangements for indoor wireless networking of information

Abstract

An optical, wavelet-based fractal modulation of ultra-short light pulses is used as part of a high-bandwidth communications system. The preferred embodiment utilizes the scheme as part of a hybrid wireless optical and RF transmission system for broadband communications among fixed and/or mobile platforms. An ultra-short pulse laser, high-power WDM-ARRAY laser or high-power incoherent light sources may be used. Computer-generated hologram techniques are employed in designing the optical transceiver subsystems for spectral encoding and decoding of wavelet patterns. Part of the design goal is to select a diversity receiver Field-of-View (FOV) in a way that the effects of scintillation are reduced by as much as possible. Compared to existing optical wireless systems, the invention offers a much higher average transmission bit rate and a much smaller bit error rate outage value, thus enabling highly available FSO links. Wireless transceiver will be capable of communications with nearly line-of-sight FSO links and will be more tolerant to shadowing. Also, the optical medium is designed to be more secure than counterparts against any intrusion.

Claims

1. A wireless optical communications system, comprising:

a source of a light pulse;

a transmitter including a modulator for modulating the light pulse with data and an optical mask for transforming the modulated light pulse into wavelets; and

a receiver including an optical mask and demodulator for recovering the data.

2. The wireless optical communications system of claim 1, wherein the source of the light pulse is a laser.

3. The wireless optical communications system of claim 1, wherein the source of the light pulse is a high-power WDM-ARRAY laser.

4. The wireless optical communications system of claim 1, wherein the source of the light pulse is a high-power incoherent source.

5. The wireless optical communications system of claim 4, wherein the incoherent source is an ultra-broadband light-emitting diode or super luminescent laser diode.

6. The wireless optical communications system of claim 1, wherein the optical mask is a holographic optical mask.

7. The wireless optical communications system of claim 1, wherein the receiver can choose to receive data in clear weather at a relatively high data rate and lower rates in the presence of turbulence.

8. The wireless optical communications system of claim 1, wherein the modulation utilizes fractal modulation.

9. The wireless optical communications system of claim 1, wherein the wavelets provide redundant copies of the transmitted data across the time-frequency plane.

10. The wireless optical communications system of claim 1, wherein multiple copies of the data are incorporated in the transmitted signal.

11. The wireless optical communications system of claim 10, wherein the multiple copies are interspersed.

12. The wireless optical communications system of claim 1, wherein the optical mask records data streams at different bit rates on spatially separate wavelength regions.

13. The wireless optical communications system of claim 1, wherein the transmitter and receiver form part of a hybrid wireless optical and RF transmission system.

14. The wireless optical communications system of claim 1, further including an erasure-correcting encoding protocol.

15. The wireless optical communications system of claim 1, wherein the encoding protocol uses Fountain codes.

16. A broadband optical wireless communications method, comprising the steps of:

generating a light pulse;

modulating the light pulse with information;

encoding the modulated light pulse into wavelets;

transmitting the wavelets to a receiver;

decoding the wavelets at the receiver; and

demodulating the pulse to recover the information.

17. The method of claim 16, wherein the steps of encoding and decoding are carried out with optical masks.

18. The method of claim 17, wherein the wherein the optical masks are holographic.

19. The method of claim 16, wherein the receiver can choose to receive data in clear weather at a relatively high data rate and lower rates in the presence of turbulence.

20. The method of claim 16, wherein the modulation utilizes fractal modulation.

21. The method of claim 16, wherein the wavelets provide redundant copies of the transmitted data across the time-frequency plane.

22. The method of claim 16, wherein multiple copies of the data are incorporated in the transmitted signal.

23. The method of claim 22, wherein the multiple copies are interspersed.

24. The method of claim 16, wherein the optical mask records data streams at different bit rates on spatially separate wavelength regions.

25. The method of claim 16, further including the step of providing an RF transmission system acting as a back-up should the optical system experience interference or failure.

26. The method of claim 16, further including the step of using an erasure-correcting encoding protocol.

27. The method of claim 26, wherein the erasure-correcting encoding protocol is based upon Fountain codes.