Controlling the phase of optical carriers
A system and method for locking the relative phase of multiple coherent optical signals, which compensates for optical phase changes induced by vibration or thermal changes in the environment.
1. A phase controlling system comprising:
an optical arrangement configured to cause interference between two or more optical channels and at least one reference beam coherently related to the two or more optical channels;
an optical detector coupled to receive the interference generated by the optical arrangement and configured to detect an interference pattern; and
a phase feedback control arrangement configured to control at least one phase of the two or more optical channels based on an output of the optical detector that is determined by the detected interference pattern.
2. The system according to claim 1 , further comprising an array of detector elements arranged to form a distributed aperture array and coupled to provide outputs to be modulated or encoded onto the two or more optical channels.
3. The system according to claim 2 , further comprising an array of optical modulators coupled to receive outputs of the detector elements and to modulate the outputs onto the optical channels.
4. The system according to claim 3 , wherein the optical modulators are further configured to control the relative phases in each element of the array.
5. The system according to claim 2 , wherein the detector elements are microwave or
millimeter-wave elements.
6. The system according to claim 2 , wherein the optical channels are routed to a central optical processing unit containing the phase controlling system.
7. The system according to claim 2 , wherein the output of the detector elements is routed to an optical processing unit via fiber optic transmission lines.
8. The system according to claim 2 , wherein the relative phases of the two or more optical channels are controlled to provide beam steering of the distributed array.
9. The system according to claim 2 , wherein the relative phases of the two or more optical channels are controlled to provide beam focus of the distributed array.
10. The system according to claim 2 , wherein the encoded signals are separated from at least one carrier of the two or more optical channels by means of an optical filter.
11. The system according to claim 1 , wherein the reference beam is dithered to enable absolute measurement of the relative phases of the two or more optical channels.
12. The method according to claim 11 , wherein the interference signal is digitized and the phase determined from the time of each transition.
13. A phase controlling method comprising:
splitting optical sources into a plurality of optical fibers,
wherein one split of the optical sources is a reference channel and the remaining splits of the optical sources are multiple optical channels;
modulating a known pattern onto the multiple channels to obtain modulated optical channels;
interfering the modulated optical channels with the reference channel; and
detecting an interference output and using the interference output to control phases of the multiple optical channels.
14. The method according to claim 13 , which further comprises modulating or encoding one or more outputs of an array of detector elements of a distributed aperture array onto at least one of the optical channels.
15. The method according to claim 14 , which further comprises coupling an array of optical modulators receive outputs of the detector elements and modulating the outputs onto the optical channels.
16. The method according to claim 15 , which further comprises the optical modulators controlling the relative phases in each element of the array.
17. The method according to claim 14 , wherein the detector elements are microwave or millimeter-wave elements.
18. The method according to claim 14 , which further comprises routing the modulated channels to a central optical processing unit containing a phase controlling system.
19. The method according to claim 14 , which further comprises routing the output of the detector elements to an optical processing unit via fiber optic transmission lines.
20. The method according to claim 14 , which further comprises controlling the relative phases of the multiple optical channels to provide beam steering of the distributed array.
21. The method according to claim 14 , which further comprises controlling the relative phases of the multiple optical channels to provide beam focus of the distributed array.
22. The method according to claim 14 , which further comprises separating the one or more modulated or coded outputs from at least one optical carrier in the multiple optical channels by means of an optical filter.
23. The method according to claim 13 , which further comprises dithering the reference channel to enable absolute measurement of the relative phases of the multiple optical channels.
24. The method according to claim 23 , which further comprises digitizing the interference output and determining a phase from one or more transition times.