Indirect optical free-space communications system and method for the broadband transmission of high-speed data
An indirect optical free-space communications system provides broadband transmission of high-speed data in transportation vehicles such as aircraft. The system includes a transmitter with a light source that can be modulated and a receiver with a photo detector, adapted to receive light that is emitted from the transmitter and to convert it into an electric signal. The transmitter and the receiver are directed onto at least one common surface, which reflects the light emitted from the transmitter before it reaches the receiver. The free space communications system is cellular and includes several cells, each of which has a transmitter and at least one corresponding receiver. The cells are configured in such a way that crosstalk with a respective adjoining cell is prevented. The cells are thus independent of one another.
1. An indirect optical free-space communication system for broadband transmission of high-speed data by way of multiple independent cells within an interior of a transportation device, comprising:
a transmitter that has a modulable light source, and
a receiver that has a photodetector to receive light emitted by the transmitter without requiring a direct line-of-sight connection between the transmitter and the receiver and without requiring cabling, said light being converted into an electric signal,
wherein the transmitter and the receiver are directed at at least one shared surface, which reflects the light emitted by the transmitter before it reaches the receiver,
wherein said transmitter is one of a plurality of transmitters and said receiver is one of a plurality of receivers,
wherein the free-space communication system is designed as a cellular system having the multiple independent cells arranged in rows within the transportation device, each of the multiple independent cells comprising one of said transmitters and at least one respective receiver, and
wherein adjacent cells of the multiple independent cells are designed to utilize different wavelengths so as to prevent crosstalk with a neighboring cell so that the cells are independent of one another.
2. The indirect optical free-space communication system as claimed in claim 1 , further comprising at least one of means for beam shaping of a respective transmitter and means for limiting a reception beam angle of a respective receiver to prevent crosstalk.
3. The indirect optical free-space communication system as claimed in claim 1 , further comprising at least one shading element for shading the light reflected by the shared surface of a cell with respect to a receiver belonging to another cell.
4. The indirect optical free-space communication system as claimed in claim 1 , wherein light sources of neighboring cells have said different wavelengths.
5. The indirect optical free-space communication system as claimed in claim 1 , wherein the at least one shared surface defines reflecting surfaces of the cells arranged in the interior of the transportation device in which the data transmission takes place.
6. The indirect optical free-space communication system as claimed in claim 5 , wherein the transportation device is a motor vehicle, airplane, ship or satellite.
7. The indirect optical free-space communication system as claimed in claim 1 , wherein reflection or scattering areas of the at least one shared surface does or do not overlap mutually within neighboring cells.
8. The indirect optical free-space communication system as claimed in claim 1 , wherein the wavelengths of the light alternate in neighboring cells.
9. The indirect optical free-space communication system as claimed in claim 1 , wherein the cells are spatially separated from one another.
10. The indirect optical free-space communication system as claimed in claim 1 , wherein the surface of at least one of the cells is a surface of a wall or an object in the interior of a space in which data is transmitted.
11. The indirect optical free-space communication system as claimed in claim 1 , wherein the light source comprises at least one LED, laser diode, edge-emitting laser diode, or VCSEL laser.
12. The indirect optical free-space communication system as claimed in claim 1 , wherein the receiver comprises a light source and the transmitter comprises a photodetector to perform bidirectional communication.
13. The indirect optical free-space communication system as claimed in claim 1 , wherein, during operation, a single transmitter of a cell supplies the data simultaneously to a plurality of receivers.
14. The indirect optical free-space communication system as claimed in claim 1 , wherein the light emitted by the transmitter of a cell is limited in its beam angle such that it does not reach the receivers of other cells.
15. The indirect optical free-space communication system as claimed in claim 1 , wherein a reception beam angle of a respective receiver of a cell is limited so that the light of the cells adjacent to the light sources does not reach the receiver.