Calibrating Optical Phased Array Transceivers Using Multi-Wavelength Light
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Solution Overview
Problem
Current fabrication techniques for large-scale optical phased arrays (OPAs) on photonic integrated circuits (PICs) lack the necessary nanometer-level tolerances for alignment and calibration, particularly in satellite-based laser communication systems where rapid movement of transmitter and receiver assemblies limits calibration time.
Innovation Solution
A system and method for calibrating PIC-based optical phased arrays using multi-wavelength light to illuminate and measure the phases of antenna elements, with internal interferometric devices and a controller to adjust phase shifters, enabling precise alignment and phasing without external feedback loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fabrication techniques are used for large-scale OPAs on PICs, then device integration is improved, but alignment precision deteriorates due to inability to achieve nanometer-level tolerances
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before final operation. The system uses calibration sources and detectors to measure actual optical path lengths and phase shifts of each antenna element prior to deployment, then stores these measurements for use during operation. This pre-characterization approach allows the system to compensate for fabrication tolerances without requiring nanometer-level manufacturing precision.
Solution Approach 2:
The patent applies parameter changes by measuring and adjusting the optical path length parameters for each antenna element. The system varies the optical path length through phase shifters to achieve the desired phase relationships between elements, compensating for variations introduced during fabrication. This allows the system to achieve precise beamforming despite manufacturing tolerances.
2Device complexity
If static alignment is relied upon in manufactured PIC-based Tx/Rx assemblies, then device complexity is reduced, but calibration time increases due to limited adjustment capability in dynamic systems
Solution Approach 1:
The patent replaces mechanical alignment adjustment mechanisms with an optical/electronic phase control system. Instead of physically adjusting component positions to achieve alignment, the system uses phase shifters to electronically control the phase of light at each antenna element. This substitution eliminates complex mechanical adjustment mechanisms while enabling rapid electronic calibration and adaptation.
Solution Approach 2:
The system performs preliminary calibration measurements to establish the actual optical characteristics of each element, then uses these pre-determined parameters for rapid electronic adjustment during operation. This approach avoids time-consuming mechanical realignment while maintaining precise control over the optical phase relationships.
3Measurement precision
If multi-wavelength calibration is performed, then measurement precision is improved, but calibration complexity increases due to need for multiple wavelength measurements
Solution Approach 1:
The patent applies multi-functionality by using the same calibration hardware (sources and detectors) to perform multiple measurement functions across different wavelengths. The system uses multi-wavelength light from the calibration sources to simultaneously or sequentially measure optical path lengths and phase shifts for multiple antenna elements, extracting multiple parameters from a single calibration sequence. This reduces the need for separate dedicated measurement systems for each parameter.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for rapid and precise calibration of transmitter and receiver elements, enabling quick establishment of communication links and maintaining alignment in dynamic satellite-based systems, improving the accuracy and reliability of large-scale OPA systems.
Implementation Method 1
A technique for calibrating the line-of-sight and phasing of the transmitter and receiver elements is provided. In some embodiments, the disclosed systems and methods include an adjunct component within a PIC that includes all of the components used for calibration. These components may include internal interferometric measurement devices
Implementation Method 2
Each waveguide may include a laser input/output and sixty-four waveguides that guide the light to sixty-four phase shifters and sixty-four antenna elements
Data Source
AI summary
A method includes 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, where each PIC includes multiple antenna elements forming an optical phased array (OPA). The method also includes determining light intensities of different wavelengths of the multi-wavelength light after the multi-wavelength light has passed through each PIC. The method further includes estimating phases of light associated with the antenna elements based on variations in the light intensities. In addition, the method includes adjusting one or more phase shifters of at least one of the PICs based on the estimated phases of light.