Optical phased array wavefront sensing and control
Aspects of the disclosure provide a method of adjusting a plurality of phase shifters of an OPA. The method may include identifying a plurality of subsets of phase shifters of the plurality of phase shifters based on an orthogonal set of functions; performing a plurality of dithers iteratively on the plurality of subsets of phase shifters of the plurality of phase shifters using the same frequency; determining a plurality of corrections based on a plurality of outputs of the OPA, each output resulting from each of the plurality of dithers; and adjusting the plurality of subsets of phase shifters of the plurality of phase shifters using the plurality of corrections, the adjustment resulting in at least one set of corrected phase shifter values.
1 . A method of adjusting a plurality of phase shifters of an optical phased array (OPA), the method comprising:
identifying a plurality of subsets of phase shifters of the plurality of phase shifters based on an orthogonal set of functions;
performing a plurality of dithers iteratively on the plurality of subsets of phase shifters of the plurality of phase shifters using the same frequency;
determining a plurality of corrections based on a plurality of outputs of the OPA, each output resulting from each of the plurality of dithers; and
adjusting the plurality of subsets of phase shifters of the plurality of phase shifters using the plurality of corrections, the adjustment resulting in at least one set of corrected phase shifter values.
2 . The method of claim 1 , wherein identifying the plurality of subsets of phase shifters of the plurality of phase shifters based on the orthogonal set of functions includes:
identifying a first subset of phase shifters of the plurality of phase shifters based on the orthogonal set of functions; and
identifying a second subset of phase shifters of the plurality of phase shifters based on the orthogonal set of functions.
3 . The method of claim 2 , wherein performing the plurality of dithers iteratively on the plurality of subsets of phase shifters of the plurality of phase shifters using the same frequency includes:
performing a first dither on the first subset of phase shifters of the plurality of phase shifters at a first time; and
performing a second dither on the second subset of phase shifters of the plurality of phase shifters at a second time following the first time.
4 . The method of claim 3 , wherein:
the first dither is performed by applying a first perturbation; and
the second dither is performed by applying a second perturbation.
5 . The method of claim 4 , wherein the first perturbation and the second perturbations are (1) sine functions or (2) cosine functions.
6 . The method of claim 5 , wherein the first perturbation is a sine function and the second perturbation is a cosine function.
7 . The method of claim 1 , wherein determining the plurality of corrections based on the plurality of outputs of the OPA includes determining a plurality of changes in phase.
8 . The method of claim 1 , wherein:
the plurality of phase shifters are arranged in a circle; and
the orthogonal set of functions is a set of circular functions.
9 . The method of claim 1 , wherein the plurality of outputs are a plurality of transmitted optical communications beams.
10 . The method of claim 1 , wherein the frequency is a terminal frequency unique to an optical communications terminal containing the OPA.
11 . The method of claim 1 , wherein the frequency is an OPA frequency unique to the OPA.
12 . A system of optical communications terminals configured to transmit and receive optical communications beams, the system comprising:
a first optical communications terminal comprising:
an optical phased array (OPA) configured to transmit and receive one or more optical communications beams, the OPA comprising a plurality of phase shifters, and
one or more processors configured to perform a plurality of dithers iteratively on a plurality of subsets of phase shifters of the plurality of phase shifters using a first terminal frequency; and
a second optical communications terminal comprising:
an OPA configured to transmit and receive one or more optical communications beams, the OPA comprising a plurality of phase shifters, and
one or more processors configured to perform a plurality of dithers iteratively on a plurality of subsets of phase shifters of the plurality of phase shifters using a second terminal frequency.
13 . The system of claim 12 , wherein the one or more processors of the first optical communications terminal are further configured to:
identify the plurality of subsets of phase shifters of the plurality of phase shifters based on an orthogonal set of functions;
determine a plurality of corrections based on a plurality of outputs of the OPA, each output resulting from each of the plurality of dithers; and
adjust the plurality of subsets of phase shifters of the plurality of phase shifters using the plurality of corrections, the adjustment resulting in at least one set of corrected phase shifter values.
14 . The system of claim 12 , wherein the first terminal frequency and the second terminal frequency are unique frequencies.
15 . The system of claim 12 , wherein the plurality of phase shifters are arranged in a circle.
16 . A method of adjusting a plurality of phase shifters of a plurality of optical phased arrays (OPA) s of a communication system, the method comprising:
performing, at a first OPA of a first optical communications terminal a first dither on a first subset of phase shifters of a plurality of phase shifters of the first OPA, wherein the first dither is performed at a first frequency;
performing, at a second OPA of a second optical communications terminal, a second dither on a second subset of phase shifters of a plurality of phase shifters of the second OPA, wherein the second dither is performed at a second frequency;
adjusting, at the first OPA of the first optical communications terminal, the first subset of phase shifters of the plurality of phase shifters based on the first dither of the first optical communications terminal; and
adjusting, at the second OPA of the second optical communications terminal, the second subset of phase shifters of the plurality of phase shifters based on the second dither of the second optical communications terminal,
wherein the first frequency is a first terminal frequency and the second frequency is a second terminal frequency.
17 . The method of claim 16 , wherein the first frequency and the second frequency do not interfere.
18 . The method of claim 16 , wherein the first dither and second dither are not coordinated.
19 . The method of claim 16 , wherein performing, at the first OPA of the first optical communications terminal, the first dither on the first subset of phase shifters of the plurality of phase shifters of the first OPA includes:
applying, at the first OPA of the first optical communications terminal, a first perturbation at the first frequency to a wavefront at the first subset of the phase shifters; and
adjusting, at the first OPA of the first optical communications terminal, an initial set of phase shifter values of the first subset of phase shifters based on the first perturbation, the adjustment resulting in a first set of phase shifter values.
20 . The method of claim 19 , further comprising:
determining, at the first OPA of the first optical communications terminal, a first correction based on a first power output of the first OPA resulting from the first dither;
wherein adjusting, at the first OPA of the first optical communications terminal, the first subset of phase shifters of the plurality of phase shifters is based on the first correction.