Asymmetric Cladding Optical Waveguide for Tight Curves
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Solution Overview
Problem
Optical polymer waveguides face significant propagation losses and limited minimum radius of curvature due to transverse losses and mode profile skewing, making it difficult to implement high-density, curved waveguide designs on printed circuit boards.
Innovation Solution
The use of an optical waveguide with asymmetric cladding distribution and a spine structure, where the cladding is thicker on one side than the other, allows for improved mode control and reduced coupling losses, enabling a smaller minimum radius of curvature without excessive propagation losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a symmetric optical polymer waveguide is used, then the fabrication process is simple and manufacturing cost is reduced, but the minimum radius of curvature is large (greater than 10 mm to 15 mm) causing significant propagation losses
Solution Approach 1:
The patent applies asymmetry by creating an optical waveguide with non-uniform cladding thickness, where the cladding layer has different thicknesses on opposite sides of the core. Specifically, the cladding thickness is greater on the inner side of the curve than on the outer side, which compensates for the mode profile skewing effect and reduces transverse losses in curved waveguides, enabling smaller minimum radii of curvature while maintaining low propagation losses
2Productivity
If the minimum radius of curvature is reduced to increase waveguide density on PCB, then more waveguides can be located in unit area, but transverse losses due to scattering of higher order modes increase significantly
Solution Approach 1:
The patent applies local quality by making the cladding thickness position-dependent, specifically varying the cladding thickness according to the local curvature of the waveguide path. The cladding is thicker on the inner side of curves and thinner on the outer side, creating a locally optimized structure that maintains mode confinement and reduces scattering losses in high-density curved waveguide configurations
3Area of stationary object
If a smaller minimum radius of curvature is implemented, then the footprint for turning corners is reduced and manoeuvrability is improved, but coupling losses increase due to mode profile skewing
Solution Approach 1:
The patent uses asymmetry in cladding distribution to counteract the symmetric mode profile skewing that occurs in curved waveguides. By making the cladding thicker on the inner side of the curve where modes tend to concentrate, the asymmetric structure compensates for the skewing effect and maintains better mode overlap between adjacent waveguide sections, thereby reducing coupling losses while enabling smaller turn radii
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 allows for a smaller minimum radius of curvature, enhancing the density and maneuverability of waveguides on PCBs while maintaining acceptable propagation losses, thus addressing the limitations of symmetric waveguides.
Implementation Method 1
the refractive index contrast at the core/cladding boundary enables an optical signal propagating along the core 11 to be confined within the core 11 by total internal reflection
Data Source
AI summary
There is provided an optical waveguide comprising an optical core having transverse sides, the optical core extending along a curved path; an optical cladding on the transverse sides of the optical core, wherein the distribution of the optical cladding on the transverse sides of the optical core is asymmetric about the centre of the core.