Optical Module Low Refractive Index Circuit Board Coupling Loss
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Solution Overview
Problem
Conventional optical modules for high-speed optical interconnects face challenges in coupling loss due to the large difference in apertures between light-emitting/receiving elements and optical waveguides, leading to signal light dispersion and increased fabrication complexity.
Innovation Solution
An optical module design featuring an optical waveguide with a low refractive-index portion surrounding a transmissive portion on a circuit board, where the signal light is reflected at the boundary surface between these two, allowing for efficient collection and transmission of signal light to a light-receiving element with a smaller aperture, reducing coupling loss and simplifying the fabrication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a common multimode waveguide is used with a light-receiving element having a small aperture for high-speed transmission, then transmission speed exceeds 20 Gbps, but coupling loss becomes large due to aperture mismatch
Solution Approach 1:
The circuit board is designed with a low refractive-index portion that specifically surrounds the transmissive portion, creating a localized refractive index gradient at the boundary. This local modification of optical properties redirects signal light toward the light-receiving element, compensating for the aperture mismatch between the waveguide and the small-aperture photodetector, thereby reducing coupling loss while maintaining high-speed transmission capability
Solution Approach 2:
The invention changes the refractive index parameter of the circuit board material in a specific region. By creating a low refractive-index portion with a different refractive index than the transmissive portion, the optical path of signal light is modified. This parameter change enables effective redirection of light without requiring a larger photodetector aperture, thus reducing coupling loss while preserving the small aperture needed for high-speed operation
2Stability of the object's composition
If the distance between the optical element and the optical waveguide is increased, then signal light dispersion is reduced, but coupling loss becomes larger
Solution Approach 1:
The low refractive-index portion is strategically positioned at the boundary between the transmissive portion and the light-receiving element. This localized modification creates an optical gradient that actively redirects dispersed signal light back toward the photodetector, compensating for the effects of increased distance without requiring the optical elements to be placed closer together
3Loss of energy
If a collecting member is provided on the circuit board to suppress signal light dispersion, then coupling loss is reduced, but fabrication complexity increases
Solution Approach 1:
The invention merges the light-collecting function with the existing circuit board structure. Instead of adding a separate collecting member, the circuit board itself is designed with a low refractive-index portion that performs the light redirection function. This integration eliminates the need for additional components and simplifies the fabrication process while still achieving effective suppression of signal light dispersion
Solution Approach 2:
The circuit board is given multiple functions: it serves as both the structural support and electrical connection medium, and simultaneously as an optical element for redirecting signal light. The low refractive-index portion embedded in the circuit board performs both structural and optical guiding functions, eliminating the need for separate collecting members and reducing overall device complexity
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 effectively suppresses signal light dispersion and reduces coupling loss, enabling efficient high-speed optical transmission while simplifying the fabrication process and reducing costs.
Implementation Method 1
the signal light is reflected toward the light-receiving element at a boundary surface between the transmissive portion and the low refractive-index portion
Implementation Method 2
the signal light transmitted through the core is completely reflected by the boundary surface between the core and the cladding
Data Source
AI summary
An optical module includes an optical waveguide that transmits and outputs signal light; a circuit board that transmits the signal light output from the optical waveguide, and includes a low refractive-index portion that neighbors and surrounds a transmissive portion and has a lower refractive index than the transmissive portion, which transmits the signal light; and a light-receiving element that includes, on a side toward the circuit board, a light-receiving portion that receives the signal light that has transmitted through the circuit board, where the signal light is reflected toward the light-receiving element at a boundary surface between the transmissive portion and the low refractive-index portion.