System and method for calibrating PIC-based optical phased array transmitter and receiver

1. A method comprising:

illuminating a photonic integrated circuit (PIC) of a transmit aperture of a laser communication terminal and a PIC of a receive aperture of the laser communication terminal with multi-wavelength light, each PIC comprising multiple antenna elements forming an optical phased array (OPA);

determining light intensities of different wavelengths of the multi-wavelength light after the multi-wavelength light has passed through each PIC starting from the multiple antenna elements;

estimating phases of light associated with the antenna elements based on variations in the light intensities; and

adjusting one or more phase shifters of at least one of the PICs based on the estimated phases of light.

2. The method of claim 1 , wherein:

the multi-wavelength light is from a single calibration source; and

the PICs are illuminated concurrently.

3. The method of claim 1 , wherein the multi-wavelength light is formed of multiple laser beams at different wavelengths that are combined using an arrayed waveguide grating (AWG).

4. The method of claim 1 , wherein the multi-wavelength light is incident on each PIC at an off-axis angle that is outside a field of regard of the PIC.

5. The method of claim 1 , further comprising:

after adjusting the one or more phase shifters of the at least one PIC, taking a measurement of emitted light to verify phasing of at least one of the OPA of the transmit aperture and the OPA of the receive aperture.

6. The method of claim 1 , wherein each of the one or more phase shifters comprises a thermo-optic or electro-optic phase modulator.

7. The method of claim 1 , wherein determining the light intensities comprises executing a stochastic parallel gradient descent algorithm.

8. The method of claim 1 , wherein a wavelength range between a shortest wavelength of the multi-wavelength light and a longest wavelength of the multi-wavelength light is approximately 10 picometers.

9. A system comprising:

a calibration source configured to illuminate a photonic integrated circuit (PIC) of a transmit aperture of a laser communication terminal and a PIC of a receive aperture of the laser communication terminal with multi-wavelength light, each PIC comprising multiple antenna elements forming an optical phased array (OPA);

one or more calibration detectors configured to:

determine light intensities of different wavelengths of the multi-wavelength light after the multi-wavelength light has propagated through each PIC starting from the multiple antenna elements; and

estimate phases of light associated with the antenna elements based on variations in the light intensities; and

a controller configured to adjust one or more phase shifters of at least one of the PICs based on the estimated phases of light.

10. The system of claim 9 , wherein the calibration source is configured to concurrently illuminate the PIC of the transmit aperture and the PIC of the receive aperture.

11. The system of claim 9 , wherein the calibration source is configured to form the multi-wavelength light from multiple laser beams at different wavelengths that are combined using an arrayed waveguide grating (AWG).

12. The system of claim 9 , wherein the calibration source is configured to illuminate the PICs such that the multi-wavelength light is incident on each PIC at an off-axis angle that is outside a field of regard of the PIC.

13. The system of claim 9 , wherein each of the one or more phase shifters comprises a thermo-optic or electro-optic phase modulator.

14. The system of claim 9 , wherein the one or more calibration detectors is configured to determine the light intensities using a stochastic parallel gradient descent algorithm.

15. The system of claim 9 , wherein a wavelength range between a shortest wavelength of the multi-wavelength light and a longest wavelength of the multi-wavelength light is approximately 10 picometers.

16. A system comprising:

a laser communication terminal comprising a transmit aperture and a receive aperture, each aperture comprising a photonic integrated circuit (PIC), each PIC comprising multiple antenna elements forming an optical phased array (OPA);

a calibration source configured to illuminate the PIC of the transmit aperture and the PIC of the receive aperture with multi-wavelength light;

one or more calibration detectors configured to:

determine light intensities of different wavelengths of the multi-wavelength light after the multi-wavelength light has passed through each PIC starting from the multiple antenna elements; and

estimate phases of light associated with the antenna elements based on variations in the light intensities; and

a controller configured to adjust one or more phase shifters of at least one of the PICs based on the estimated phases of light.

17. The system of claim 16 , wherein the calibration source is configured to concurrently illuminate the PIC of the transmit aperture and the PIC of the receive aperture.

18. The system of claim 16 , wherein the calibration source is configured to form the multi-wavelength light from multiple laser beams at different wavelengths that are combined using an arrayed waveguide grating (AWG).

19. The system of claim 16 , wherein the calibration source is configured to illuminate the PICs such that the multi-wavelength light is incident on each PIC at an off-axis angle that is outside a field of regard of the PIC.

20. The system of claim 16 , wherein each of the one or more phase shifters comprises a thermo-optic or electro-optic phase modulator.