Systems and methods for underwater optical communication

Abstract

The systems and methods of the invention provide for improved underwater communication systems. In particular, the systems and methods of the invention provide for improved underwater optical modems including optical transmitters and optical receivers that allow omni-directional transmission and reception of optical signals underwater and having a range of about 100 m and allowing data rates greater than 1 Mbit/s. The systems and methods of the invention also provide for underwater communication networks having a plurality of optical modems communicating with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures depict certain illustrative embodiments of the invention in which like reference numerals refer to like elements. These depicted embodiments may not be drawn to scale and are to be understood as illustrative of the invention and not as limiting in any way.

FIG. 1 depicts a high-level block diagram of an optical communication system according to the invention.

FIG. 2 is a graph depicting the relationship between attenuation coefficient of electromagnetic radiation and wavelength of the electromagnetic radiation in water and seawater.

FIG. 3 is a more detailed block diagram of a transmitter according to one illustrative embodiment of the invention.

FIG. 4 is a more detailed block diagram of a receiver according to one illustrative embodiment of the invention.

FIG. 5 is a network architecture for an underwater communication system according to one illustrative embodiment of the invention.

FIG. 6A-6C are charts depicting the direction of propagation of electromagnetic radiation from a transmitter according to the invention.

FIG. 7 is a graph depicting the relationship between the average power required to transmit electromagnetic radiation in the optical spectrum and range of transmission.

FIG. 8 depicts underwater communication between a seafloor observatory and an unmanned underwater vehicle according to one implementation of the invention.

FIG. 9 depicts underwater communication between an underwater unmanned vehicle and two seafloor observatories according to one implementation of the invention.

FIG. 10 depicts a transmitter including a plurality of sources and a diffuser according to one illustrative embodiment of the invention.

Claims

1. An underwater communication system, comprising: a transmitter having a source capable of emitting electromagnetic radiation, and a diffuser capable of diffusing the electromagnetic radiation and disposed in a position surrounding a portion of the source for diffusing the electromagnetic radiation in a plurality of directions, anda receiver having a detector capable of detecting electromagnetic radiation, such that the electromagnetic radiation can be received in substantially any direction;wherein, the transmitter and receiver are physically separated from each other, andwherein, the electromagnetic radiation includes electromagnetic waves of wavelength in the optical spectrum between 300 nm and 800 nm.

2. The system of claim 1, wherein the transmitter includes a plurality of sources.

3. The system of claim 2, wherein each of the plurality of sources are individually controllable.

4. The system of claim 1, wherein the transmitter includes an electronic circuit to drive the source.

5. The system of claim 4, wherein the electronic circuit includes at least one of an emitter coupled logic design, a cascode configured design, and a totem pole-type design.

6. The system of claim 4, wherein the electronic circuit includes at least one of a field effect transistor, and a bipolar device.

7. The system of claim 1, wherein the transmitter comprises an etalon to modulate the electromagnetic radiation from the source.

8. The system of claim 1, wherein the receiver comprises a diffuser capable of diffusing the electromagnetic radiation and disposed in a position surrounding a portion of the detector.

9. The system of claim 8, wherein the receiver is capable of receiving the electromagnetic radiation along a radius of a hemispherical region.

10. The system of claim 1, wherein the receiver includes an electronic circuit to prevent the saturation of the detector.

11. The system of claim 10, wherein the electronic circuit includes an automatic gain control circuit.

12. The system of claim 1, wherein the diffuser is formed from at least one of a discrete reflective element, a discrete refractive element and a high transmission scattering medium.

13. The system of claim 1, wherein the diffuser is integrally formed with the detector.

14. The system of claim 1, wherein the diffuser is integrally formed with the source.

15. The system of claim 1, wherein the diffuser is disposed on top of the source.

16. The system of claim 1, wherein the diffuser is capable of diffusing the electromagnetic radiation in a plurality of directions along a radius of a hemispherical region.

17. The system of claim 1, wherein the diffuser is formed from silicone, TiO2.

18. The system of claim 1, wherein the source includes at least one of a light emitting diode, a laser diode, and a photodiode.

19. The system of claim 1, wherein the source is embedded in the diffuser.

20. The system of claim 1, wherein the detector includes a photomultiplier tube.

21. The system of claim 3, wherein the photomultiplier tube includes a large-aperture, hemispherical photomultiplier tube.

22. An underwater communication system, comprising: two or more nodes that can transmit and receive electromagnetic radiation, each node including: a transmitter having a source capable of emitting electromagnetic radiation, and a diffuser capable of diffusing the electromagnetic radiation and disposed in a position surrounding a portion of the source for diffusing the electromagnetic radiation in a plurality of directions, anda receiver having a detector capable of detecting electromagnetic radiation, such that the electromagnetic radiation can be received in substantially any direction;wherein, the two or more nodes are physically separated from each other, andwherein, the electromagnetic radiation includes electromagnetic waves of wavelength in the optical spectrum between 300 nm and 800 nm.

23. The system of claim 22, wherein the power of transmission of the electromagnetic radiation is kept fairly constant over time.

24. The system of claim 22, wherein each of the two or more nodes transmit and receive the electromagnetic radiation at a rate of approximately 1 Mbps or higher.

25. The system of claim 22, wherein the two or more nodes are separated from each other by a distance of approximately 100 m or higher.

26. A system of claim 22, wherein at least one of the two or more nodes includes a mobile unit.

27. A system of claim 22, wherein at least one of the two or more nodes includes a stationary unit.

28. A method of manufacturing an optical modem for an underwater optical communication system, comprising the steps of providing at least one source of optical radiation,disposing the at least one source within a diffuser such that the electromagnetic radiation emitted from the source is diffused in a plurality of different directions,providing at least one detector configured to receive and detect optical radiation from a plurality of different direction, and