Curved Fiber Array Unit for Warped PIC Optical Coupling
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Solution Overview
Problem
The increasing size and complexity of optical communication networks, coupled with the use of thru-silicon vias and varied fiber types, lead to packaging challenges due to PIC warpage and misalignment of optical signals, particularly in warped or non-linear profiles.
Innovation Solution
The implementation of a fiber array unit (FAU) with a substrate featuring V-grooves of varying depths and widths, aligned along a curve to accommodate photonic device warpage, and a lid with a mismatched coefficient of thermal expansion (CTE) to align optical channels with waveguides, ensuring efficient coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If PIC thickness is reduced using thru-silicon vias, then integration density is improved, but PIC warpage increases causing optical coupling misalignment
Solution Approach 1:
The patent applies curvature by forming V-grooves along a curved path on the FAU substrate rather than a straight line. This curved arrangement of V-grooves compensates for the warpage induced by TSV processing in thin PICs, maintaining proper optical coupling alignment between the fiber array and waveguides despite the reduced PIC thickness
Solution Approach 2:
The patent changes the geometric parameters of the V-grooves by varying their depths along the curved path. This parameter variation allows the fiber array to conform to the warped profile of the thin PIC, ensuring that optical signals remain properly aligned with waveguides despite thickness reduction and associated warpage
2Adaptability or versatility
If various types of fibers are used to couple optical signals, then coupling versatility is improved, but alignment complexity increases
Solution Approach 1:
The patent creates a universal FAU structure with V-grooves that can accommodate multiple types of optical fibers (single-mode, multi-mode, different diameters) through a single standardized interface. The curved V-groove design provides a flexible platform that adapts to various fiber types without requiring separate alignment mechanisms for each fiber type
Solution Approach 2:
The patent applies local quality by allowing each V-groove to have customized depth and positioning along the curved path, while maintaining a standardized overall structure. This enables optimization for specific fiber types at local positions while preserving universal compatibility across the entire fiber array
3Reliability
If FAU lid CTE is mismatched with substrate, then thermal expansion compensation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent deliberately selects an FAU lid material with a higher coefficient of thermal expansion (CTE) than the substrate material. This CTE mismatch is engineered to compensate for substrate warpage during thermal cycling, as the lid expands more than the substrate to maintain the curved V-groove alignment with the PIC waveguides under varying temperature conditions
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 FAU provides flexible alignment of optical fibers with photonic devices, maintaining efficient optical coupling despite warpage and temperature changes, enhancing alignment efficiency and reducing packaging challenges.
Implementation Method 1
a variable FAU lid formed from a second material with a second CTE, where the first CTE is lower than the second CTE
Data Source
AI summary
The fiber array units (FAUs) described herein include an FAU substrate with a coupling surface, an array of V-grooves formed in a FAU substrate, and a plurality of optical channels individually disposed in a respective V-groove of the array of V-grooves. The array of V-grooves and the optical channels are configured to position the optical channels along a curve defined in the coupling surface such that the optical channels are aligned with waveguides in a warped photonic device.