Defocuser for compact free space communication

1. A device for free space optical communication comprising:

a defocuser configured to receive an optical signal from a laser and control a beam divergence of the optical signal, wherein the optical signal comprises a data signal and a beacon signal; and

a controller configured to cause the defocuser to adjust the beam divergence to a first beam divergence for a first operational mode and a second beam divergence for a second operational mode, wherein the first operational mode comprises a communication mode and the second operational mode comprises one or more of a tracking mode or a link acquisition mode, and wherein a single aperture is used for the first operational mode and the second operational mode, and wherein the single aperture is used for both transmission of the optical signal into free space and receiving optical signals from one or more communication devices via free space.

2. The device of claim 1 , wherein the defocuser comprises an adjustable lens configured to control the beam divergence.

3. The device of claim 2 , wherein the adjustable lens comprises a liquid lens configured to change shape, in response to an electrical signal, to modify the beam divergence.

4. The device of claim 2 , wherein the defocuser is configured to control the beam divergence by adjusting a distance between the adjustable lens and a source of the optical signal.

5. The device of claim 1 , wherein the second beam divergence is wider than the first beam divergence.

6. The device of claim 1 , wherein the defocuser enables use of the laser and output optics for both the communication mode and one or more of the tracking mode or the link acquisition mode.

7. The device of claim 1 , wherein the defocuser and the controller are comprised in a satellite.

8. A method for free space optical communication comprising:

adjusting, based on a first operational mode, a defocuser to a first setting configured for a first beam divergence, wherein the first operational mode comprises a data communication mode;

receiving, from a laser, a first optical signal;

modifying, using the defocuser adjusted to the first setting, the first optical signal to have the first beam divergence;

adjusting, based on a second operational mode, the defocuser to a second setting configured for a second beam divergence, wherein the second operational mode comprise one or more of a tracking mode or a link acquisition mode;

receiving, from the laser, a second optical signal;

modifying, using the defocuser adjusted to the second setting, the second optical signal to have the second beam divergence; and

outputting one or more of the modified first optical signal or the modified second optical signal, wherein a single aperture is used for the first operational mode and the second operational mode, and wherein the single aperture is used for both receiving optical signals from one or more communication devices via free space and transmission to the one or more communication devices via free space of one or more of the modified first optical signal or the modified second optical signal.

9. The method of claim 8 , wherein the defocuser comprises an adjustable lens configured to control beam divergence.

10. The method of claim 9 , wherein the adjustable lens comprises a liquid lens configured to change shape, in response to an electrical signal, to modify the beam divergence.

11. The method of claim 9 , wherein adjusting the defocuser to the first setting comprises adjusting a distance between the adjustable lens and a source of the optical signal to a first distance, and wherein adjusting the defocuser to the second setting comprises adjusting the distance between the adjustable lens and the source of the optical signal to a second distance different than the first distance.

12. The method of claim 8 , wherein the second beam divergence is wider than the first beam divergence.

13. The method of claim 8 , wherein the defocuser enables use of the laser and output optics for both the communication mode and one or more of the tracking mode or the link acquisition mode.

14. A system for free space optical communication comprising:

a first optical terminal; and

a second optical terminal configured to communicate with the first optical terminal, wherein one or more of the first optical terminal or the second optical terminal comprises:

a defocuser configured to receive an optical signal from a laser and control a beam divergence of the optical signal, wherein the optical signal comprises a data signal and a beacon signal; and

a controller configured to cause the defocuser to adjust the beam divergence to a first beam divergence for a first operational mode and a second beam divergence for a second operational mode, wherein the first operational mode comprises a communication mode and the second operational mode comprises one or more of a tracking mode or a link acquisition mode, wherein a single aperture of the first optical terminal is used for the first operational mode and the second operational mode, and wherein the single aperture is used for both transmission of the optical signal from the first optical terminal and receiving optical signals from the second optical terminal.

15. The system of claim 14 , wherein the defocuser comprises an adjustable lens configured to control the beam divergence.

16. The system of claim 15 , wherein the adjustable lens comprises a liquid lens configured to change shape, in response to an electrical signal, to modify the beam divergence.

17. The system of claim 15 , wherein the defocuser is configured to control the beam divergence by adjusting a distance between the adjustable lens and a source of the optical signal.

18. The system of claim 14 , wherein the second beam divergence is wider than the first beam divergence.