Optically Variable Filter Array Calibration for WDM Crosstalk
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optically variable filter arrays for WDM systems face challenges in achieving a flat-top spectral waveform pattern with low crosstalk and efficient wavelength selection, due to the unsuitability of Lorentzian and Gaussian filter configurations, and increased power consumption from TO effects.
Innovation Solution
A calibration method for an optically variable filter array apparatus using a two-dimensionally arranged wavelength selection element, where voltage control of pixels allows for precise wavelength selection and variation of light passage characteristics, enabling correlation detection between pixel coordinates and wavelengths, and measurement of insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a Fabry-Perot interferometer filter configuration is used, then the filter can be implemented with a specific structure, but the peak range of selected wavelength becomes too narrow and the spectral waveform pattern becomes Lorentzian which is unsuitable for WDM signals
Solution Approach 1:
The patent transforms the spectral waveform pattern from Lorentzian to flat-top by changing the filtering mechanism parameters. Instead of using Fabry-Perot interferometer resonance, the invention employs a diffraction grating combined with a wavelength selection element that can be controlled to produce a flat-top spectral pattern, making it suitable for WDM signal selection where multiple wavelength components need to be included with low crosstalk.
2Device complexity
If conventional filter configurations (Lorentzian or Gaussian) are used, then the filter structure is simple, but the crosstalk between adjacent channels increases and the flat-top spectral waveform pattern cannot be achieved
Solution Approach 1:
The patent segments the wavelength selection function into two parts: a diffraction grating that disperses wavelengths spatially, and a wavelength selection element (such as a liquid crystal display or digital micromirror device) that selectively controls which wavelengths pass through. This segmentation allows achieving flat-top spectral pattern with low crosstalk while maintaining reasonable device complexity.
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary element between the input WDM signals and the wavelength selection element. The grating disperses the wavelengths in the spatial domain, allowing the selection element to control each wavelength independently, thereby reducing crosstalk and achieving the desired flat-top spectral waveform pattern.
3Adaptability or versatility
If TO effects are exploited for wavelength tuning, then the filter can change selected wavelengths, but the power consumption increases for array configuration
Solution Approach 1:
The patent replaces the thermal-optic (TO) effect-based wavelength tuning mechanism with a mechanically controllable diffraction grating system combined with an electrically controlled wavelength selection element. Instead of heating elements to change refractive index for wavelength tuning, the invention uses a mechanically adjustable grating or a selection element that can be electrically switched to select different wavelengths, significantly reducing power consumption while maintaining wavelength adaptability.
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
Enables accurate selection of desired wavelengths for WDM signals with reduced crosstalk and optimized power consumption by determining pixel relationships with wavelengths and applied voltages, improving the filter's spectral performance and efficiency.
Implementation Method 1
varying light passage characteristics by controlling a voltage to be applied to each of the pixels
Implementation Method 2
at least a single wavelength-dispersion light beam which is dispersed according to wavelength
Data Source
AI summary
In a wavelength selection element employed in an optically variable filter array apparatus, pixels in a line form are placed into a light reflection state so that wavelength-scanned light can be incident on the optically variable filter array apparatus. On the basis of the wavelength of scanned reflection light and the location of the pixel in a light reflection state at a timing of acquisition of output, the relationship between the x coordinate of the wavelength selection element and wavelength is determined. This makes it possible to achieve calibration of the optically variable filter array apparatus capable of selection of a desired wavelength with respect to a desired channel from multi-channel WDM light.