Graded Waveguide Optical Coupler for Low-Loss SDM-WDM Interfaces
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Solution Overview
Problem
Existing optical couplers face challenges in achieving low-loss, high-coupling coefficient interfaces between conventional optical fibers and optical waveguide devices, particularly with multichannel devices having closely spaced waveguides.
Innovation Solution
The optical coupler array employs a common single coupler housing structure with a plurality of longitudinal waveguides, including vanishing core waveguides, to optically couple multiple optical fibers to an optical device. This design features a relative refractive index relationship and gradually modified core sizes and spacing along the optical element to ensure efficient light coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical fibers are used to interface with optical waveguide devices having different core sizes and NAs, then compatibility with existing fiber infrastructure is maintained, but insertion losses increase and coupling coefficients decrease
Solution Approach 1:
The patent introduces an optical waveguide device with graded core sizes as an intermediary component between conventional optical fibers and multichannel waveguide devices. This intermediate waveguide acts as a transition element that gradually adapts the optical mode from the conventional fiber to the smaller multichannel waveguides, reducing mode field mismatch and improving coupling efficiency while minimizing insertion losses.
Solution Approach 2:
The patent employs parameter changes by designing waveguides with gradually varying core sizes along the propagation direction. The core diameter transitions from larger values at the input (matching conventional fibers) to smaller values at the output (matching multichannel waveguides). This continuous parameter change enables smooth mode transformation and reduces abrupt impedance mismatches, thereby lowering insertion losses and improving coupling coefficients.
2Area of stationary object
If channel spacing is reduced to increase device integration density, then device compactness improves, but alignment precision and coupling accuracy deteriorate
Solution Approach 1:
The patent divides the optical coupling function into multiple segments: the conventional fiber interface, the graded-waveguide transition section, and the multichannel waveguide array. This segmentation allows each section to be optimized independently - the transition section can be designed with larger effective mode fields to tolerate spacing variations, while the compact multichannel array maintains small pitch. The segmented approach decouples the alignment sensitivity from the final channel spacing.
Solution Approach 2:
The patent addresses the spacing-precision tradeoff by introducing a longitudinal dimension for gradual transformation. Instead of attempting to couple directly between widely spaced fibers and closely spaced waveguides, the graded waveguide extends in the propagation direction, providing a extended interaction region where mode transformation occurs gradually. This longitudinal extension compensates for the reduced transverse spacing tolerance.
3Adaptability or versatility
If dissimilar NA waveguide devices are interfaced to enable functionality, then system versatility improves, but coupling efficiency and signal quality deteriorate
Solution Approach 1:
The patent uses parameter changes to bridge dissimilar NA waveguide devices. The graded-waveguide transition section features a continuous variation in core size and refractive index profile, which transforms the numerical aperture gradually from the input waveguide NA to the output waveguide NA. This continuous parameter transformation reduces abrupt mode field distortions and minimizes signal quality degradation while enabling interfacing of dissimilar waveguide types.
Solution Approach 2:
The patent employs composite waveguide structures combining different materials with varying refractive indices to achieve the desired NA transformation. The graded-waveguide may incorporate multiple material layers or compositions that provide the required refractive index profile, enabling efficient mode transformation between dissimilar waveguides while maintaining signal integrity through optimized material selection and结构设计.
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 solution achieves a low-loss, high-coupling coefficient interface with high accuracy and easy alignment, effectively addressing the challenges of interfacing dissimilar NA waveguide devices and multichannel devices.
Implementation Method 1
optical waveguide devices based on refractive index contrast or numerical aperture (NA) waveguides
Implementation Method 2
optical coupler array employs a common single coupler housing structure with a plurality of longitudinal waveguides
Implementation Method 3
gradually modified core sizes and spacing along the optical element to ensure efficient light coupling
Data Source
AI summary
Wavelength division multiplexers for space division multiplexing can include wavelength division multiplexing fanout devices or pump-signal combiners for multicore fibers.