Super-Gaussian Optical Filter for ASE Noise Attenuation
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Solution Overview
Problem
Existing wavelength tunable filters in optical communication networks struggle to effectively attenuate ASE noise outside the passband while maintaining precise alignment of the passband with the center wavelength of optical signals, particularly in high-capacity WDM networks with 400 Gbps signals, due to their Gaussian-shaped amplitude-frequency characteristics.
Innovation Solution
The optical transmission system employs a bandpass filter with a convex-shaped gain curve defined by a super Gaussian function, combined with a telecentric optical system and a movable element like a tilting mirror, to adjust the passband and reduce ASE noise by controlling the angle of the mirror surface based on power measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a wavelength tunable filter with Gaussian-shaped amplitude-frequency characteristic is used, then the passband can be smoothly adjusted, but the slope of the gain curve is gentle making it difficult to greatly attenuate ASE noise from adjacent channels
Solution Approach 1:
The patent changes the mathematical parameter of the amplitude-frequency characteristic from Gaussian to super Gaussian function, increasing the order parameter n to achieve steeper slopes while maintaining the convex shape for precise control
Solution Approach 2:
The patent combines the super Gaussian function (providing steep noise attenuation) with the convex function shape (providing precise passband control) to create a composite characteristic that achieves both goals simultaneously
2Productivity
If the passband is shifted around the center wavelength of the optical signal, then frequency utilization can be optimized, but the power measured by the power monitor shows no significant change making precise alignment difficult
Solution Approach 1:
The patent changes the shape parameter of the passband characteristic from flat (rectangular) to convex shape, creating a pronounced peak at the center wavelength that provides strong measurement feedback for precise alignment while allowing frequency shifting
3Object-affected harmful factors
If a rectangular-shaped amplitude-frequency characteristic is used, then noise outside the passband can be greatly attenuated, but the curve in the passband is flat making it difficult to precisely align the passband center with the optical signal center
Solution Approach 1:
The patent changes the shape parameter from rectangular (flat top) to convex shape, creating a curved passband that provides both steep noise attenuation at the edges and a pronounced center peak for precise alignment feedback
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 configuration allows for effective noise attenuation outside the passband while minimizing signal loss, enabling accurate alignment of the passband center with the optical signal center, thus enhancing signal-to-noise ratio and frequency utilization efficiency.
Implementation Method 1
a transmission grating 35. The transmitted diffraction light from the transmission grating 35 is reflected by the reflecting mirror 39
Implementation Method 2
The transmitted diffraction light from the transmission grating 35 is reflected by the reflecting mirror 39
Implementation Method 3
a telecentric optical system, the telecentric optical system comprising at least a lens to adjust a direction of propagation of each of the dispersed multiple wavelength components
Data Source
AI summary
An optical filter is configured to selectively pass, as an output light, at least one wavelength component of multiple wavelength components included in an input light. The optical filter comprises a movable element. A controller is configured to adjust a passband by controlling the movable element based on power of light corresponding to the output light measured by a power monitor. The optical filter is configured as a filter so that in a first wavelength band including a center wavelength of the passband, a gain curve corresponds to a convex function having a peak at the center wavelength and in a second wavelength band adjacent to the first wavelength band, the gain curve shows a stepper slope than the convex function.