Calibrating Combined Interferometers Using Orthogonal Dithering
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Solution Overview
Problem
Existing calibration methods for optical devices like IQ phase modulators are inefficient, as they often require blocking branches with threshold biases, which can damage the device and are time-consuming, especially at high optical powers, and involve excessive complexity and cost with photo-detector monitoring.
Innovation Solution
A combined interferometer structure is calibrated by maintaining collinearity of optical field vectors using orthogonal dithering signals applied to a parent and child interferometers, allowing concurrent calibration without blocking branches, thus reducing damage risk and calibration time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If threshold biases are applied to block branches for calibration, then calibration can be performed, but device damage risk increases and calibration time increases
Solution Approach 1:
The patent replaces the mechanical/blocking approach (using threshold biases to block branches) with an optical field manipulation approach (using dithering signals to control interferometer phases). This substitution eliminates the need for high-power blocking that causes damage while maintaining calibration capability through controlled optical phase modulation.
Solution Approach 2:
The patent employs periodic dithering signals applied to the interferometer branches to enable calibration. By using periodic modulation rather than static blocking, the system achieves calibration through time-varying phase changes that do not require high-power threshold biases, thus reducing device damage risk while maintaining measurement precision.
2Measurement precision
If threshold biases are applied to block branches for calibration, then calibration can be performed, but calibration time increases
Solution Approach 1:
The patent enables continuous calibration operation by applying dithering signals that allow concurrent measurement and calibration without requiring sequential blocking and unblocking operations. This continuous approach eliminates idle time associated with threshold bias switching and significantly reduces total calibration time while maintaining accuracy.
Solution Approach 2:
By using periodic dithering signals, the patent enables overlapping calibration operations that proceed continuously rather than sequentially. The periodic nature of the signals allows for time-efficient calibration where multiple measurement cycles can occur within a single calibration sequence, reducing overall calibration time.
3Measurement precision
If photo-detector monitoring is used for calibration, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing interferometer branches serve multiple functions: they simultaneously perform data modulation during normal operation and self-calibration during calibration mode. By using the same optical paths and components for both functions, the system eliminates the need for separate photo-detector monitoring systems, reducing complexity while maintaining precision.
Solution Approach 2:
The calibration process uses the interferometer's own optical fields and phases for self-calibration without requiring external detection systems. The dithering signals applied to the interferometer branches generate measurable effects within the same optical path, enabling the system to calibrate itself without additional photo-detectors or monitoring equipment.
4Measurement precision
If conventional calibration methods are used, then calibration can be performed, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs dynamic phase adjustment through dithering signals to compensate for manufacturing tolerances and alignment variations. By continuously modulating the phases during calibration, the system can adapt to slight misalignments and achieve accurate calibration without requiring extremely tight manufacturing precision, as the dynamic adjustment compensates for static alignment errors.
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 method enables efficient calibration of optical devices at high optical powers without damage, reducing calibration time and complexity, and achieving accurate alignment of interferometer branches.
Implementation Method 1
An electro-optic device, such as an electro-optic IQ phase modulator, may be used to encode data, represented by a set of electrical signals, into the phase and/or amplitude of light as the light passes through the IQ phase modulator
Implementation Method 2
a combined interferometer structure may include a parent interferometer, a first child interferometer, and a second child interferometer forming a combined interferometer structure
Data Source
AI summary
A device may include a plurality of interferometers. The plurality of interferometers may include a parent interferometer, a first child interferometer coupled to a first branch of the parent interferometer, and a second child interferometer coupled to a second branch of the parent interferometer. At least one of the plurality of interferometers may be calibrated by maintaining collinearity of an output of the first branch and the second branch and using perturbation signals.