Optical Wavemeter Calibration Using Moore-Penrose Decoupling
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Solution Overview
Problem
Existing optical wavemeters face challenges in achieving high resolution and accuracy due to uncertainties in fabrication, reliance on ideal component behaviors, and complex nonlinear data processing, which leads to inefficient and impractical calibration methods.
Innovation Solution
A method and apparatus for calibrating an optical wavemeter using a linear system model, employing Moore-Penrose signal processing techniques to decouple variables and estimate optical parameters more independently, allowing for reliable and accurate wavemeter calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If nonlinear data processing techniques are used for wavemeter calibration, then measurement precision can be improved, but device complexity and difficulty of implementation increase significantly
Solution Approach 1:
The patent segments the calibration problem by separating the determination of optical parameters (transmission coefficients, phase shifts) from the wavelength measurement process. The calibration phase independently characterizes system components using known wavelength signals, storing these parameters for later use. During actual measurement, only simple lookup and calculation operations are needed, avoiding complex nonlinear processing during the measurement phase while maintaining high precision.
Solution Approach 2:
The patent performs preliminary calibration actions before actual wavelength measurements. During calibration, the system pre-determines all optical parameters including transmission coefficients of beam splitters, phase shifts in delay lines, and coupling efficiencies. These pre-computed parameters are stored and reused during measurement operations, eliminating the need for repeated complex nonlinear calculations and significantly simplifying the measurement process.
2Measurement precision
If calibration methods depend on absolute optical power levels, then measurement accuracy can be improved, but reliability decreases due to difficulty in obtaining accurate power measurements
Solution Approach 1:
The patent extracts and eliminates the dependency on absolute optical power level measurements from the calibration process. Instead of requiring accurate power measurements, the method uses only the relative intensity ratios between different photodetector outputs, which can be measured more reliably. The calibration algorithm processes only intensity ratio data, removing the problematic absolute power measurement requirement while maintaining calibration accuracy.
3Ease of manufacture
If existing calibration approaches are used, then wavemeter functionality can be achieved, but manufacturing precision requirements increase due to sensitivity to fabrication uncertainties
Solution Approach 1:
The patent implements a self-calibration mechanism that automatically compensates for fabrication variations. The calibration process uses actual measured intensity ratios from the specific device being calibrated, allowing each wavemeter to self-characterize its own optical parameters regardless of manufacturing tolerances. This self-service approach eliminates the need for tight manufacturing precision by adapting to each device's actual characteristics through measurement-based calibration.
Solution Approach 2:
The patent changes the calibration approach from relying on fixed design parameters to using measured intensity ratios as the basis for calibration. Instead of assuming ideal component behaviors with precise manufacturing specifications, the method dynamically determines actual optical parameters (transmission coefficients, phase shifts) through measurement of intensity ratios during calibration, making the system robust to manufacturing variations.
4Device complexity
If simple delay line based interferometers are used, then device complexity is reduced, but measurement precision deteriorates due to fabrication uncertainties
Solution Approach 1:
The patent performs preliminary calibration to pre-determine all optical parameters of the simple delay line interferometer, including the actual length difference between delay lines, beam splitter ratios, and phase shifts. These pre-characterized parameters compensate for fabrication uncertainties, allowing the simple interferometer structure to achieve high measurement precision through software-based correction rather than requiring complex hardware design.
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
The proposed solution enables efficient and effective calibration of wavemeters, achieving sub-GHz accuracy and simplifying integration into various devices, while reducing dependence on initial conditions and absolute optical power levels.
Implementation Method 1
an optical delay line structure having two unequal-length waveguides each configured to receive a respective one of said two portions
Implementation Method 2
Simple delay line based interferometers for example have been shown to be effective in absolute frequency measurement
Implementation Method 3
obtaining a corresponding set of measurements from a plurality of photodetectors
Data Source
AI summary
There is provided a method, apparatus and system for calibrating and operating an optical wavemeter. In calibration, training optical signals with known wavelengths are input to a wavemeter, and corresponding photodetector measurements are obtained. Optical parameters of the wavemeter are then estimated based on the measurements. The optical parameters are indicative of a length difference ΔL between two unequal-length waveguides in an optical delay line of the wavemeter; and scattering parameters of a multi-mode interferometer (MMI) coupler of the wavemeter. The estimation process involves a (e.g. golden-section) search to determine one or more output values for at least one of the optical parameters, based on an objective function which indicates a difference expected and actual measurements. The expected measurements are generated based on a numerical model incorporating candidate values for the optical parameters.