Claims
- 1. A method of improving a signal-to-noise (S/N) ratio for a light signal transmitted by wireless optical communication through adverse environmental conditions, the light signal including a snake component and a ballistic component for carrying coded information, and a diffusive component that adds to background noise, the method comprising the steps of:
encoding information to be transmitted by the light signal, wherein the light signal is one of a serial train of code pulses or a modulated light beam; selecting an appropriate wavelength for the encoded light signal; transmitting the encoded light signal though the adverse environmental conditions; receiving the encoded light signal; sorting the received encoded light signal to preferentially select the information carrying components and reduce the diffusive component; and detecting the sorted encoded light signal with a photo-detector.
- 2. The method of claim 1, wherein the step of selecting the appropriate wavelength comprises selecting a wavelength to optimize absorption of light such that a magnitude of the snake component and the ballistic component is enhanced relative to the diffusive component.
- 3. The method of claim 1, wherein the step of selecting the appropriate wavelength comprises selecting a wavelength near the absorption band of water droplets, in the 800 to 1800 nm range.
- 4. The method of claim 1, wherein the step of selecting the appropriate avelength comprises selecting a wavelength near the absorption band of active pecies in the adverse environmental conditions.
- 5. The method of claim 1, wherein the light signal is one of polarized light, linearly polarized light, or circularly polarized light.
- 6. The method of claim 1, wherein the step of sorting the received encoded light signal comprises at least one of time gating, space gating, or polarization filtering the received light signal.
- 7. The method of claim 6, wherein the step of space gating is performed by a spatial aperture.
- 8. The method of claim 6, wherein the step of space gating is performed by a Fourier space gate.
- 9. The method of claim 6, wherein the step of time gating is performed by at least one of a time-gated detector, a streak camera, a gated intensified CCD camera, or an optical Kerr gate.
- 10. The method of claim 6, wherein the step of polarization filtering is performed by at least one of a Wollaston Prism or a polarizing cube beam splitter used to split the received light signal into a parallel-polarized component and a perpendicular-polarized component;
whereby the parallel-polarized component and the perpendicular-polarized component are detected, and their temporal profiles are subtracted to reduce the diffusive component and extract the information carrying components with a higher S/N ratio.
- 11. The method of claim 10, wherein the temporal profiles of the parallel-polarized component and the perpendicular-polarized component are measured using at least one time-gated detector.
- 12. The method of claim 10, wherein a calibration factor ξ is used to account for a difference in sensitivity and accuracy of the parallel-polarized component and the perpendicular-polarized component, and the value of ξ is determined by requiring IA−ξIB=0, where IA and IB are intensities of the parallel-polarized component and the perpendicular-polarized component, respectively, and introducing an unpolarized light beam into the polarizing cube beam splitter.
- 13. The method of claim 10, wherein a theoretical formalism of the detected temporal profiles, based on an analytical solution of a time-dependent polarized radiative transfer equation are used to extract the encoded information.
- 14. The method of claim 13, wherein the analytical solution of the time-dependent polarized radiative transfer equation to quickly and accurately compute a photon distribution in an infinite uniform turbid medium up to an arbitrary high order is software-based.
- 15. The method of claim 14, wherein an algebraic expression of spatial cumulants of a photon distribution function I(r, s, t) at any angle and time is provided for both polarized and unpolarized light signals exact up to an arbitrary higher.
- 16. A method of improving a signal-to-noise ratio for a light signal transmitted by wireless optical communication through adverse environmental conditions, the light signal including a snake component and a ballistic component for carrying coded information, and a diffusive component that adds to background noise, the method comprising the steps of:
encoding information to be transmitted by the light signal, wherein the light signal is encoded in parallel in a 2-D array; selecting an appropriate wavelength for the encoded light signal; transmitting the encoded light signal though the adverse environmental conditions; receiving the transmitted encoded light signal; sorting the received encoded light signal to preferentially select the information carrying components and reduce the diffusive component; and detecting the sorted encoded light signal with a photo-detector.
- 17. The method of claim 16, wherein the step of selecting the appropriate wavelength comprises selecting a wavelength to optimize absorption of light such that a magnitude of the snake component and the ballistic component is enhanced relative to the difflusive component.
- 18. The method of claim 16, wherein the step of selecting the appropriate wavelength comprises selecting a wavelength near the absorption band of water droplets, in an 800 to 1800 nm range.
- 19. The method of claim 16, wherein the step of selecting the appropriate wavelength comprises selecting a wavelength near the absorption band of active species in the adverse environmental conditions.
- 20. The method of claim 16, wherein the light signal is one of polarized light, linearly polarized light, or circularly polarized light.
- 21. The method of claim 16, wherein the step of sorting the received encoded light signal comprises at least one of time gating, space gating, or polarization filtering the received light signal.
- 22. The method of claim 21, wherein the step of space gating is performed by a spatial aperture.
- 23. The method of claim 21, wherein the step of space gating is performed by a Fourier space gate.
- 24. The method of claim 21, wherein the step of time gating is performed by at least one of a time-gated detector, a streak camera, a gated intensified CCD camera, or an optical Kerr gate.
- 25. The method of claim 21, wherein the step of polarization filtering is performed by at least one of a Wollaston Prism or a polarizing cube beam splitter used to split the received light signal into a parallel-polarized component and a perpendicular-polarized component;
whereby the parallel-polarized component and the perpendicular-polarized component are detected, and their temporal profiles are subtracted to reduce the diffusive component and extract the information carrying components with a higher S/N ratio.
- 26. The method of claim 25, wherein the temporal profiles of the parallel-polarized component and the perpendicular-polarized component are measured using at least one time-gated image intensified 2-D CCD camera.
- 27. The method of claim 25, wherein a calibration factor ξ is used to account for a difference in sensitivity and accuracy of the parallel-polarized component and the perpendicular-polarized component, and the value of ξ is determined by requiring IA−ξIB=0, where IA and IB are intensities of the parallel-polarized component and the perpendicular-polarized component, respectively, and introducing an unpolarized light beam into the polarizing cube beam splitter.
- 28. The method of claim 25, wherein a theoretical formalism of the detected temporal profiles, based on an analytical solution of a time-dependent polarized radiative transfer equation are used to extract the encoded information.
- 29. The method of claim 28, wherein the analytical solution of the time-dependent polarized radiative transfer equation to quickly and accurately compute a photon distribution in an infinite uniform turbid medium up to an arbitrary high order is software-based.
- 30. The method of claim 29, wherein an algebraic expression of spatial cumulants of a photon distribution function I(r, s, t) at any angle and time is provided for both polarized and unpolarized light signals exact up to an arbitrary higher order.
PRIORITY
[0001] This application claims priority to a provisional application entitled “Methods to Improve Line of Sight Wireless Optical Communication Through Adverse Environmental Conditions” filed in the United States Patent and Trademark Office on Apr. 4, 2001 and assigned U.S. Ser. No. 60/281,437, the contents of which are hereby incorporated by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60281437 |
Apr 2001 |
US |