Bi-directional optical communications system and corresponding method

• US 7,991,294 B2
• Filed: 11/19/2007
• Issued: 08/02/2011
• Est. Priority Date: 12/04/2006
• Status: Active Grant

• Current Assignee: Thales Alenia Space Schweiz AG (Thales SA)
• Original Assignee: Oerlikon Space AG (Government of Switzerland)
• Inventors: Tüchler, Michael, Dreischer, Thomas
• Primary Examiner(s): SINGH, DALZID E
• Application Number:
  US11/942,070
• Publication Number:
  US 20080131134A1
• Time in Patent Office: 1,352 Days
• Field of Search: 398128-131, 398/135, 398/137, 398/138, 398/41, 398/140, 398/141, 398/156, 398/158
• US Class Current: 398/137
• CPC Class Codes: H03L 7/08 Details of the phase-locked loop
• CPC Class Codes: H04B 10/118 specially adapted for satellite communication
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation
• CPC Class Codes: H04L 5/1469 using time-sharing

Abstract

Bi-directional laser communications system comprising a first transceiver and a second transceiver for establishing two optical channels there between. The first transceiver comprises a first transmitter with a pulsed high-power laser source for transmitting a pulsed beacon laser signal into a first of said optical channels. The second transceiver comprises a receiver with an optical antenna for receiving said pulsed beacon laser signal, said second transceiver and/or a receiving optic of said second transceiver being adjustable so that it can be adjusted with respect to said pulsed beacon laser signal. The second transceiver further comprises a second transmitter with a laser for transmitting a high energy laser signal into a second of said optical channels, and means for a separation of said first optical channel and said second optical channel. These means prevent the high energy laser signals from being transmitted into said second optical channel whenever said pulsed beacon laser signal is expected to arrive through said first optical channel.

Claims

1. Bi-directional laser communications system comprising a first transceiver and a second transceiver for establishing two optical channels there between, wherein

said first transceiver comprises a first transmitter with a pulsed high-power laser source for transmitting optical beacon pulses into a first of said optical channels,

said second transceiver comprises

a receiver with a receiving optic for receiving said optical beacon pulses, said second transceiver and/or a receiving optic of said second transceiver being adjustable so that it can be adjusted with respect to the direction of said optical beacon pulses,

a second transmitter with a laser for transmitting a high energy laser signal into a second of said optical channels, and

means for synchronization of said first optical channel and said second optical channel, said means preventing said high energy laser signals from being transmitted into said second optical channel whenever said optical beacon pulses are expected to arrive through said first optical channel.

2. The communications system of claim 1, wherein said optical beacon pulses are transmitted into said first optical channel with a pre-defined repetition rate and wherein said second transceiver is able to synchronize on the basis of pulses of said optical beacon pulses.

3. The communications system of claim 2, wherein after synchronization said means are aware when to prevent said high energy laser signals from being transmitted.

4. The communications system of claim 1, wherein said second optical channel is a long distance downlink and wherein a pulse-position modulation (PPM) scheme is applied in said second transceiver prior to the transmission of said high energy laser signal, where pulses of a pulse width of less than 50 ns, preferably equal to or less than 10 ns are emitted.

5. The communications system of claim 4, wherein a pulse-position modulation scheme is applied in said first transceiver prior to the transmission of said optical beacon pulses, and wherein due to the application of the pulse-position modulation scheme a service channel is embedded in or provided by said first optical channel.

6. The communications system of claim 4, wherein a forward-error correction scheme, preferably a turbo-coding scheme, is applied in said second transceiver in order to deal with transmission errors introduced by suppression of said high energy laser signals whenever said optical beacon pulses are expected to arrive.

7. The communications system of claim 6, wherein a decoding scheme is employed in said first transceiver in order to calculate said transmission errors, which are deterministic errors.

8. The communications system of claim 1, wherein said first optical channel is a long distance beacon uplink and wherein the pulses of the optical beacon pulses have a pulse width of less than 100 ns, preferably less than 10 ns, and are emitted with a repetition frequency in the range between 1 kHz and 100 kHz and preferably in the range between 4 kHz and 32 kHz.

9. The communications system of claim 1, wherein said high-power laser source of the first transceiver has an optical output power which is at least 100 times higher than the optical output power of a laser of said second transmitter.

10. The communications system of claim 1, wherein link budgets of said first optical channel and said second optical channel are different, but where the signal-to-noise ratio (SNR) at the respective receiving optics is similar.

11. The communications system of claim 1, wherein a digital phase-locked-loop is employed in said second transceiver in order to lock the pulses of said optical beacon pulses.

12. The communications system of claim 1, wherein the communications system is one of a point-to-point

space-to-ground, preferably deep space-to-ground/aerial vehicle,

ground/aerial vehicle-to-space, preferably ground-to-deep space, or

air-to-air,

communications system.

13. The communications system of claim 1 being a point-to-point ground-to-ground communications system where said optical channels at least partially run through or touch the atmosphere.

14. Method for bi-directional laser-based communication between a first transceiver and a second transceiver, characterized by the following steps:

generating a series of optical beacon pulses by said first transceiver and transmission of said optical beacon pulses across a first optical channel to said second transceiver,

receiving and processing said optical beacon pulses by said second transceiver in order to enable said second transceiver and/or a receiving optic of said second transceiver to be adjusted with respect to the direction of said first optical channel,

adjusting said second transceiver and/or a receiving optic of said second transceiver with respect to said first optical channel,

generating high energy laser signals by said second transceiver for transmission across a second optical channel to said first transceiver,

transmitting said high energy laser signals across the second optical channel to said first transceiver when no optical beacon pulse is expected to arrive at said second transceiver, and

suppressing transmission of said high energy laser signals when an optical beacon pulse is expected to arrive at said second transceiver.

15. The method of claim 14, wherein:

the steps of generating said series of optical beacon pulses comprises generating said series of optical beacon pulses to have a pre-defined repetition rate, and

the steps of transmitting and suppressing include performing a synchronization inside said second transceiver on the basis of pulses of said optical beacon pulses.

16. The method of claim 14, comprising the step:

applying a pulse-position modulation (PPM) scheme in said second transceiver prior to the transmission of said high energy laser signal, where pulses of a pulse width of less than 50 ns, preferably equal to or less than 10 ns, are emitted.

17. The method of claim 14, wherein the pulses of the optical beacon pulses on a long distance beacon uplink have a pulse width of less than 100 ns, preferably less than 10 ns, and are emitted with a repetition frequency in the range between 1 kHz and 100 kHz and preferably in the range between 4 kHz and 32 kHz.

18. The method of claim 14, comprising the step:

applying a pulse-position modulation scheme in said first transceiver prior to the transmission of said optical beacon pulses, wherein due to the application of the pulse-position modulation scheme a service channel is embedded or provided.

19. The method of claim 14, comprising the step:

applying a forward-error correction scheme, preferably a turbo-coding scheme, in said second transceiver in order to deal with transmission errors introduced by a suppression of said high energy laser signals whenever said optical beacon pulses are expected to arrive.