Concentric CMOS Photodiode Array for Spatial De-multiplexing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spatial domain multiplexing (SDM) systems in optical fiber communications require tedious alignment and are prone to environmental perturbations due to the use of lens/photodiode combinations for de-multiplexing, which hinders mass production and reliability.
Innovation Solution
A novel array of concentric photodiodes using CMOS technology is developed to detect and de-multiplex optical energies carried by spatially multiplexed channels, providing a robust and efficient solution for SDM systems, which can be fabricated using standard 0.25 um CMOS technology and packaged in open cavity packaging for exposure to incident light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lens/photodiode combination is used for de-multiplexing, then spatially multiplexed channels can be detected, but alignment is tedious and system is prone to environmental perturbations
Solution Approach 1:
The patent merges the lens and photodiode into an integrated structure where the photodiode array is positioned at the focal plane of the lens, eliminating the need for separate alignment of these components. This integration directly resolves the alignment complexity and stability issues by making the relative position fixed and precise.
Solution Approach 2:
The lens serves multiple functions: it focuses the optical signals onto the photodiode array and simultaneously provides the structural framework for the integrated device. This multi-functionality reduces the number of separate components that need alignment, thereby improving reliability while managing device complexity.
2Reliability
If lens/photodiode combination is used for de-multiplexing, then spatially multiplexed channels can be detected, but system is prone to environmental perturbations
Solution Approach 1:
By integrating the lens and photodiode array into a single device, the patent eliminates the sensitive mechanical connections and air-glass interfaces that exist in separate component systems. This integration makes the system more robust to environmental perturbations such as temperature changes and vibrations.
Solution Approach 2:
The patent replaces the mechanical alignment system with an optically integrated system where the focal plane relationship is built into the device structure. This substitution eliminates the need for mechanical adjustment mechanisms that are susceptible to environmental perturbations.
3Productivity
If standard CMOS technology is used for photodiode fabrication, then mass production is enabled, but detection precision and optical properties must be maintained
Solution Approach 1:
The patent optimizes the photodiode design parameters specifically for CMOS fabrication, including adjusting the photodiode area, depletion region depth, and doping profiles to achieve high detection precision within the constraints of standard CMOS process capabilities. This allows mass production while maintaining optical performance.
Solution Approach 2:
The patent implements different structural characteristics in different regions of the photodiode array, with each photodiode optimized for its specific detection requirements. This local optimization allows the entire array to be fabricated using standard CMOS processes while each element maintains high detection precision.
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 concentric photodiode array effectively de-multiplexes optical energies, offering improved alignment stability and environmental robustness, enabling mass production and high-frequency detection capabilities while maintaining compatibility with photonics industry requirements.
Implementation Method 1
A unique and novel array of concentric photodiodes using CMOS technology is shown to detect and reliably de-multiplex optical energies carried by the spatially multiplexed channels
Data Source
AI summary
An octagonal structure of photodiodes using standard CMOS technology has been developed to serve as a de-multiplexer for spatially multiplexed fiber optic communication systems.