Systems, methods, and structures for optical phased array calibration via interference

Patent metadata

Field	Value
Publication number	US-10790585-B2
Application number	US-201916279885-A
Country	US
Kind code	B2
Filing date	Feb 19, 2019
Priority date	Feb 16, 2018
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

Aspects of the present disclosure describe systems, methods, and structures for optical phased array calibration that advantageously may be performed as a single-pass measurement of phase offset with respect to only a single interference measurement. In sharp contrast to the prior art—systems, methods, and structures according to aspects of the present disclosure advantageously produce phase offsets and phase functions of each element without time-consuming iterative procedures or multiple detector signals as required by the prior art.

First claim

The invention claimed is:

1. An optical structure comprising:
a substrate upon which is formed;
an array of optical phase shifters;
an array of optical antennas in optical communication with the array of optical phase shifters;
an output optical distribution network in optical communication with the array of optical antennas; and
a detector element in optical communication with the output optical distribution network;

wherein said optical structure is configured such that light traversing the optical phase shifters is phase shifted, the phase shifted light is directed to the optical antennas where at least a portion is transmitted therethrough, the transmitted light from all of the phase shifters is directed to the output optical distribution network and subsequently to the detector element which detects the transmitted phase shifted light as an interference signal, said interference signal including light from all of the phase shifters in the array of optical phase shifters, wherein individual optical paths between the optical antennas and the detector element are all equal in length.

2. The optical structure of claim 1 , wherein the detector element comprises a plurality of individual detectors.

3. The optical structure of claim 2 , wherein the plurality of individual detectors is electrically connected in parallel.

4. The optical structure of claim 2 , wherein the plurality of individual detectors is arranged in sets of multiple detectors, each set including the same number of individual detectors, and each set being electrically connected in parallel.

5. The optical structure of claim 4 , wherein there are two sets of multiple detectors electrically connected in parallel.

6. The optical structure of claim 2 , wherein each one of the individual detectors receives light transmitted through predetermined ones of the array of optical antennas.

7. The optical structure of claim 6 , wherein the number of predetermined ones of the array of optical antennas transmitting light to an individual one of the detectors is the same for all of the individual detectors in the plurality of detectors.

8. The optical structure of claim 1 , further comprising:
an input distribution network formed upon the substrate and in optical communication with the array of optical phase shifters, said input distribution network configured to receive light from a source and distribute the received light to the array of optical phase shifters.

9. The optical structure of claim 1 , wherein determined phase offsets for the structure are valid over a wide band of wavelengths.

10. An optical structure comprising:
a substrate upon which is formed;
an input optical distribution network;
an array of optical phase shifters in optical communication with the input optical distribution network;
an array of optical antennas in optical communication with the array of optical phase shifters;
an array of reflector elements, in optical communication with the array of optical phase shifters,
a detector element in optical communication with, and positioned in an optical path before the array of optical phase shifters;

wherein said optical structure is configured such that light traversing the optical phase shifters is phase shifted, the phase shifted light is directed toward the array of reflector elements where at least a portion of the phase shifted light is reflected from at least one of the reflector elements back through the optical phase shifters and subsequently directed as an interference signal to the detector element which detects the interference signal.

11. The optical structure according to claim 10 , wherein the interference signal includes light phase shifted by all the optical phase shifters in the array of optical phase shifters.

12. The optical structure according to claim 10 , wherein the portions of light combined into the interference beam traverse a respective one of the optical phase shifters more than once.

13. The optical structure according to claim 10 , wherein the detector element comprises a plurality of individual detectors.

14. The optical structure according to claim 13 , wherein each one of the plurality of detectors receives light from predetermined ones of the array of optical reflectors.

15. The optical structure according to claim 10 , wherein the detector element is a coherent detector having an input local oscillator.

16. The optical structure according to claim 15 , wherein the coherent detector is a balanced detector or IQ detector.

17. The optical structure according to claim 10 , wherein the array of optical reflectors is positioned in an optical path between the array of optical phase shifters and the array of optical antennas.

18. The optical structure according to claim 10 , wherein the array of optical reflectors is positioned in an optical path after the array of optical antennas.

19. The optical structure according to claim 10 , wherein the array of optical reflectors is formed in the array of optical antennas as a wavelength independent, distributed reflector in each.

20. The optical structure according to claim 10 , wherein the array of optical reflectors comprises of the array of optical antennas wherein each individual one of the antennas exhibits a wavelength dependent Bragg condition.

21. A method for calibrating an optical structure, the optical structure comprising a substrate onto which is formed an array of phase shifting elements in optical communication with an array of emitting antenna elements, the method comprising:
directing individual light signals through the phase shifting elements such that the individual light signals are phase shifted;
directing the phased shifted light signals to the array of emitting antennas;
for each individual one of the array of phase shifting elements,
varying an amount of phase shift imparted by the individual phase shifting element over a pre-determined pattern, and
detecting interference signals produced by the phase shifted light signals, wherein the varying is performed while detecting the interference signals, and wherein the interference signals include light from all of the phase shifting elements; and

determining an overall phase offset for each phase shifting element with respect to at least one of the interference signals detected.

22. The method according to claim 21 , further comprising:
determining a phase vs. voltage relationship for each one of the individual phase shifting elements in the array.

23. The method according to claim 21 , further comprising:
determining an attenuation vs. voltage relationship for each one of the individual phase shifting elements in the array.

24. The method according to claim 21 , wherein while varying an amount of phase shift for an individual phase shifting element all other phase shifting elements are not varied.

25. The method according to claim 21 , further comprising:
varying an amount of phase shift for several of the phase shifting elements at different frequencies; and
determining a phase offset of each frequency component in the interference signal.

Assignees

• Analog Photonics LLC

Inventors

• Poulton Christopher
• Russo Peter
• Timurdogan Erman
• Byrd Matthew
• Vermeulen Diedrik
• Hosseini Ehsan

Classifications

• H04B10/25753

  Distribution optical network, e.g. between a base station and a plurality of remote units · CPC title

• H01Q3/2676 Primary

  Optically controlled phased array · CPC title

• G02F1/2955 Primary

  by controlled diffraction or phased-array beam steering (controlled diffraction for optical waveguide switching G02F1/313) · CPC title

• G02F1/292 Primary

  by controlled diffraction or phased-array beam steering (controlled diffraction for optical switching G02F1/31) · CPC title