Parallelepiped WDM Filters for Compact Optical Modules
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Solution Overview
Problem
In high-speed optical communication systems, the reduction in filter size and pitch between channels in WDM Mux/DeMux devices poses a challenge in aligning filters without contact, as conventional cuboid filters do not efficiently utilize space, leading to ineffective optical paths and increased insertion loss.
Innovation Solution
The use of filters with a parallelepiped shape, featuring a cutting angle not equal to 90 degrees, allows for a fully utilized effective optical path, enabling compact optical modules with improved dimensions and insertion loss performance by redirecting light beams between reflecting parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional cuboid filters are used in WDM Mux/DeMux devices, then the structure is simple and easy to manufacture, but the space utilization is inefficient and insertion loss increases
Solution Approach 1:
The patent applies asymmetry by changing the filter shape from a conventional symmetric cuboid to an asymmetric parallelepiped with a specific cutting angle (α). This asymmetric geometry allows the filter to better match the optical beam path, enabling the beam to pass through the entire filter volume without early termination. The cutting angle is specifically designed so that the beam exits the filter at the opposite corner, maximizing the effective optical path length and reducing insertion loss while maintaining manufacturability through standard cutting processes.
2Volume of moving object
If filter size and pitch are reduced to meet compact module requirements, then the module dimensions are improved, but the risk of filter contact increases and alignment becomes more difficult
Solution Approach 1:
The asymmetric parallelepiped shape with cutting angle α creates an optimized beam exit position that improves alignment tolerance. The slanted cutting face directs the beam to exit at a specific corner of the filter, providing a well-defined exit point that is less sensitive to positioning variations. This geometric design allows for reduced pitch between filters while maintaining reliable alignment and reducing the risk of contact between adjacent filters in compact WDM modules.
Solution Approach 2:
The patent utilizes the third dimension by introducing a cutting angle in the vertical dimension of the filter geometry. Instead of simply reducing filter size in the horizontal plane, the slanted cut extends the optical path through the filter thickness, effectively using the vertical dimension to increase the effective optical path length. This dimensional approach allows compact packaging while maintaining optical performance.
3Loss of energy
If the effective optical path is maximized in conventional filters, then insertion loss is reduced, but the filter volume and pitch requirements increase
Solution Approach 1:
The asymmetric cutting geometry allows the optical beam to traverse the maximum possible distance through the filter material by exiting at the far corner rather than through a face. This asymmetric path optimization achieves effective optical path lengths comparable to or greater than conventional filters, but within a more compact volume due to the efficient use of the filter's three-dimensional space.
Solution Approach 2:
The patent maximizes the optical path length by utilizing the vertical thickness dimension of the filter through the slanted cutting angle. The beam enters one face and exits through the slanted cut surface, traversing a longer path through the filter material without requiring a larger horizontal footprint. This dimensional optimization allows reduced filter volume while maintaining low insertion loss.
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 design enhances the utilization of space in WDM Mux/DeMux devices, reducing the risk of filter contact and improving performance in compact optical modules, supporting higher bandwidth applications like CFP4 and QSFP-28 form-factors.
Implementation Method 1
a dielectric thin film filter (TFF) transmits a selected wavelength band of the multiple-wavelength collimated light passed by a corresponding channel port
Implementation Method 2
a dielectric thin film filter (TFF) transmits a selected wavelength band of the multiple-wavelength collimated light
Implementation Method 3
reflect all other wavelengths
Data Source
AI summary
Filters shaped differently from those commonly used in WDM Mux/DeMux optical devices are described. Different from the prior art devices that commonly use filters shaped in cuboid, the filters in the embodiment of the present invention are shaped in parallelepiped. In other words, a cross section of such filter is not in parallelogram. According to one embodiment of the present invention, a filter is so cut that a cross section thereof presents a cutting angle not being 90 degrees. As a result, the filter is fully used in WDM Mux/DeMux optical devices. Such filters are advantageously used in compact optical modules.