Across water-air interface communication method and system

1. A method for transmitting information across a water-air interface with a ultraviolet (UV) beam, the method comprising:

emitting the UV beam in a first, free medium, with a first optical wireless communication device;

measuring a scintillation index of the UV beam in a second, free medium, different from the first, free medium, at a second optical wireless communication device, wherein the scintillation index is an indicator of weather conditions at the water-air interface;

selecting, based on the weather conditions and a value of the scintillation index, a modulation scheme for the UV beam; and

modulating the UV beam with the selected modulation scheme,

wherein the UV beam has a wavelength in a range of 100 to 400 nm.

2. The method of claim 1 , wherein the modulation scheme is one of a on-off-keying (OOK) and orthogonal-frequency division multiplexing (OFDM).

3. The method of claim 1 , further comprising:

embedding a predetermined identification code into the UV beam.

4. The method of claim 3 , further comprising:

responding to the first optical wireless communication device with a value of the measured scintillation index only if the second optical wireless communication device determines that the predetermined identification is known.

5. The method of claim 4 , wherein the first optical wireless communication device selects the modulation scheme based on the received scintillation index.

6. The method of claim 1 , further comprising:

determining a height of a water wave at the water-air interface; and

selecting a first modulation scheme if the height of the water wave is larger than a predetermined threshold, and selecting a second modulation scheme if the height of the water wave is smaller than the predetermined threshold,

wherein the first medium is air or water and the second medium is water or air, respectively.

7. The method of claim 1 , wherein the first optical wireless communication device is attached to a submarine, or sensor probe, or remote operated vehicle, or a diver, and the second optical wireless communication device is attached to an aircraft or unmanned aerial vehicle.

8. The method of claim 1 , wherein no acoustic signal is used.

9. The method of claim 1 , wherein the UV beam propagates through water, the water-air interface and then air, between the first and second optical wireless communication devices.

10. A method for transmitting information across a water-air interface with a ultraviolet (UV) beam, the method comprising:

emitting the UV beam in a first, free medium, with a first optical wireless communication device;

estimating a height of a water wave at the water-air interface, with a second optical wireless communication device that is located in a second, free medium, different from the first, free medium;

selecting, based on a value of the height of the water wave, a modulation scheme for the UV beam; and

modulating the UV beam with the selected modulation scheme,

wherein the UV beam has a wavelength in a range of 100 to 400 nm, and

wherein the first medium is air or water and the second medium is water or air, respectively.

11. The method of claim 10 , wherein the modulation scheme is one of an on-off-keying (OOK) and an orthogonal-frequency division multiplexing (OFDM).

12. The method of claim 10 , further comprising:

embedding a predetermined identification code into the UV beam.

13. The method of claim 12 further comprising:

responding to the first optical wireless communication device with a value of the estimated height of the water wave only if the second optical wireless communication device determines that the predetermined identification is known.

14. The method of claim 13 , wherein the first optical wireless communication device selects the modulation scheme based on the received height of the water wave.

15. The method of claim 10 , further comprising:

measuring a scintillation index of the UV beam in air, at the second optical wireless communication device; and

selecting a first modulation scheme if a value of the scintillation index is larger a given threshold, and selecting a second modulation scheme if the value of the scintillation index is smaller than the given threshold.

16. The method of claim 10 , wherein the first optical wireless communication device is attached to a submarine, and the second optical wireless communication device is attached to an aircraft.

17. The method of claim 10 , wherein no acoustic signal is used.

18. The method of claim 10 , wherein the UV beam propagates through water, the water-air interface and then air, between the first and second optical wireless communication devices.

19. A system for transmitting information across a water-air interface with a ultraviolet (UV) beam, the system comprising:

a first optical wireless communication device configured to emit in water the UV beam;

a second optical wireless communication device configured to measure a parameter; and

a controller that is configured to select, based on a value of the measured parameter, a modulation scheme for the UV beam,

wherein the first optical wireless communication device modulates the UV beam with the selected modulation scheme, and

wherein the UV beam has a wavelength in a range of 100 to 400 nm, and

wherein the parameter is a scintillation index associated with weather conditions at the water-air interface, or a height of water waves at the water-air interface.