WDM Filter Cascade Layout for Uniform Channel Power Budgets
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Solution Overview
Problem
Existing WDM systems face challenges in achieving uniform power budgets across channels due to varying transmission losses and dispersion penalties, leading to the need for high-cost APD chips or the inconvenience of using two types of chips, which increases production and maintenance complexity.
Innovation Solution
A WDM structure with first and second wavelength division multiplexers, each comprising N filtering units, where filtering units are grouped and cascaded in series or series-parallel combinations, with cascade positions and modes determined to ensure uniform total power budgets across channels, allowing for the use of low-cost DML+PIN chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the TFF scheme is adopted with uniform pairwise insertion losses design, then the insertion loss of the wavelength division multiplexer is reduced and cost is lowered, but the total power budget varies significantly across different wavelengths, causing some channels to exceed the capability of low-cost DML+PIN chips
Solution Approach 1:
The patent applies local quality by designing different cascade positions for filtering units corresponding to different wavelengths. Specifically, filtering units for wavelengths with larger dispersion penalties are positioned closer to the line side interface, while those with smaller penalties are positioned farther away. This non-uniform arrangement compensates for wavelength-dependent transmission losses and dispersion penalties, achieving uniform total power budgets across all channels while maintaining cost-effective TFF technology.
2Reliability
If high-cost APD chips are used to meet the power budget requirements of all channels, then the reliability and capability are improved, but the cost increases significantly
Solution Approach 1:
The patent changes the parameter of cascade position for different filtering units to compensate for wavelength-dependent power budget variations. By adjusting the position of filtering units in the cascade structure based on their corresponding wavelengths' transmission characteristics and dispersion penalties, the system achieves uniform total power budgets that enable all channels to use low-cost DML+PIN chips instead of requiring high-cost APD chips.
3Reliability
If two types of chip schemes (DML+PIN and APD) are adopted to match different power budget requirements, then the power budget uniformity is improved, but the device complexity and maintenance difficulty increase
Solution Approach 1:
The patent applies homogeneity by making all channels use the same type of low-cost DML+PIN chips. This is achieved by designing the cascade structure of filtering units to compensate for wavelength-dependent losses, creating uniform total power budgets across all channels. The homogeneous chip type simplifies production processes, reduces inventory complexity, and eases maintenance management compared to using mixed chip types.
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 solution achieves uniform total power budgets across channels, reducing costs by using low-cost DML+PIN chips and simplifying production and maintenance, while maintaining flexibility for different channel scenarios.
Implementation Method 1
Each filtering unit corresponds to one central wavelength
Data Source
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AI summary
Disclosed is a wavelength division multiplexing structure.. The wavelength division multiplexing structure comprises a first wavelength division multiplexer and a second wavelength division multiplexer; the first wavelength division multiplexer and the second wavelength division multiplexer each comprise N filtering units, branch side interfaces correspondingly connected to the filtering units, and a line side interface, N being a positive integer; each filtering unit corresponds to one center wavelength; the line side interface of the first wavelength division multiplexer and the line side interface of the second wavelength division multiplexer are connected by means of an optical fiber; the N filtering units are divided into multiple groups, and the multiple groups of filtering units are cascaded in a series connection mode or the multiple groups of filtering units are cascaded in a combined mode of series connection and parallel connection; the filter units in each group of filter units are cascaded in a series connection mode; and the cascade modes and/or cascade positions corresponding to the filter units in the first wavelength division multiplexer and the second wavelength division multiplexer are at least related to the center wavelengths corresponding to the filter units.