Optical Fiber Connector Mirror for Low-Profile Grating Coupling
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Solution Overview
Problem
Existing methods for coupling optical fibers to photonic integrated circuits (PICs) face challenges in tolerance, manufacturability, cost, and complexity, particularly with quartz fiber arrays and angled polished fibers, which are expensive and add height to packaged PICs.
Innovation Solution
A concave reflective ellipsoidal surface profile and optical fiber alignment structure are integrated through precision stamping, allowing the optical fiber axis to be oriented at small angles parallel to the PIC surface, reducing the connector's profile and improving alignment, manufacturability, and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If grating couplers are used to couple light from optical fibers to PICs, then wafer-level testing becomes possible and packaging costs are reduced, but alignment tolerances become more stringent and the connector height increases
Solution Approach 1:
A mode field adapter is introduced as an intermediary component between the optical fiber and the grating coupler. This adapter transforms the mode field of the optical fiber to match the mode field requirements of the grating coupler, thereby relaxing alignment tolerance requirements while maintaining coupling efficiency. The adapter serves as a mediator that bridges the mismatch between fiber and grating coupler characteristics.
2Adaptability or versatility
If quartz fiber arrays are used to terminate optical fibers, then standard pitch positioning is achieved, but manufacturing cost increases and tolerance becomes greater than 1 micrometer
Solution Approach 1:
The patent replaces expensive, precision-ground quartz fiber arrays with a more economical solution using standard optical fibers and a mode field adapter. The adapter is designed to be cost-effective while providing the necessary mode field transformation. This substitution maintains pitch positioning capability through standard fiber arrays while significantly reducing manufacturing cost and improving alignment tolerance to below 1 micrometer.
3Reliability
If angled polished optical fibers are used with grating couplers, then mode field matching is achieved, but device complexity and packaging height increase
Solution Approach 1:
Instead of angling the optical fiber end face to match the grating coupler angle, the patent inverts the approach by keeping the fiber end face perpendicular and instead angling the mode field adapter. This inversion simplifies the fiber preparation process and reduces connector complexity while achieving the same mode field matching effect. The adapter contains the angular transformation internally rather than requiring it in the fiber itself.
4Productivity
If optical fibers are butt-coupled normal to the PIC surface, then wafer testing is enabled, but the connector height increases due to fiber bend radius requirements
Solution Approach 1:
The patent addresses the height issue by changing the spatial arrangement of components. The mode field adapter is designed with a compact structure that minimizes the vertical space required. Additionally, the adapter allows for optimized fiber routing that reduces the bend radius requirement, thereby reducing the overall connector height while maintaining wafer-level testing capability.
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 provides precise, low-profile optical coupling that matches the mode field of angled polished fibers, enhancing tolerance, ease of use, and reliability while reducing production costs and package height.
Implementation Method 1
light from the optical fibers is coupled in/out of the PIC using diffractive grating couplers
Implementation Method 2
a mirror is provided to turn light to/from the optical fiber
Data Source
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AI summary
To couple light between an optical fiber and a grating coupler of a photonic integrated circuits, a mirror is provided to turn light to/from the optical fiber to allow the axis of the optical fiber to be oriented at small angles or parallel to the surface of the PIC, and lowered close to the surface of the PIC. The mirror is further configured to reshape light from a flat polished optical fiber to produce a mode field resembling the mode field of an angled polished optical fiber, to match the design angle of existing grating couplers that are designed to work with angled polished optical fibers. The mirror and optical fiber alignment structure in the optical connector are integrally/simultaneous formed by precision stamping.