Non-Imaging Lens Assembly for Small-Area Photodetector Coupling
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Solution Overview
Problem
Existing optical communication systems face challenges in efficiently coupling light from multimode fibers to small-area photodetectors while minimizing power loss and preventing photodetector damage from high peak irradiance.
Innovation Solution
A non-imaging lens system comprising a first and second lens is used to relay light from a multimode fiber onto a photodetector, with the second lens positioned in contact or close proximity, distributing light evenly and filtering it to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single lens is used to focus light from multimode fiber to photodetector, then the system is simple, but the light distribution is uneven causing high peak irradiance that may damage the photodetector
Solution Approach 1:
The patent divides the single lens system into two separate lenses: a first lens for collecting light from the multimode fiber and a second lens for redistributing it onto the photodetector. This segmentation allows each lens to be optimized for its specific function, with the second lens specifically designed to create uniform light distribution and prevent peak irradiance damage to the photodetector.
Solution Approach 2:
The patent introduces an intermediary element - a diffuser or scattering medium - between the second lens and the photodetector. This intermediary redistributes the light uniformly across the photodetector surface, eliminating high peak irradiance while maintaining overall light transmission efficiency.
2Productivity
If the photodetector area is made smaller to match fiber core size, then coupling efficiency improves, but the photodetector becomes more vulnerable to peak irradiance damage
Solution Approach 1:
The patent segments the optical path into two distinct lens functions: the first lens collects light from the multimode fiber, and the second lens redistributes it onto the small-area photodetector. This allows the photodetector to maintain a small area for high coupling efficiency while the second lens ensures uniform light distribution to prevent peak irradiance damage.
Solution Approach 2:
The patent changes the light distribution parameters by introducing a second lens with specific focal length and aperture characteristics. This lens transforms the light profile from concentrated to uniformly distributed across the photodetector surface, enabling small photodetector areas to operate safely without peak irradiance damage.
3Illumination intensity
If conventional imaging lenses are used, then light can be focused, but aberrations increase and assembly tolerances become more difficult to control
Solution Approach 1:
The patent segments the optical system into two specialized lenses rather than using a single conventional imaging lens. The first lens is optimized for light collection from the fiber, and the second lens is optimized for uniform redistribution onto the photodetector. This segmentation reduces aberrations and makes the system less sensitive to assembly tolerances compared to conventional single-lens imaging systems.
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 lens system enhances light capture and distribution, increasing photodetector lifetime and operational range while reducing aberrations and assembly tolerances, and protecting the photodetector from high peak irradiance.
Implementation Method 1
The first lens is positioned between the optical fiber and the second lens and is configured to relay light from the optical fiber to the second lens
Implementation Method 2
The second lens is positioned between the first lens and the photodetector and is configured to focus light from the first lens onto the photodetector
Data Source
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AI summary
The disclosure provides for an optical communication device (100) that includes a photodetector (146), an optical fiber (142), a first lens (302), and a second lens (304). The optical fiber may be configured to relay light. The first lens (302) may include a first surface (310) and a second surface (312) and has an image plane (308). The first lens (302) may be configured to receive the light output from the optical fiber (142), where the received light has a first cross-sectional area at the first surface (310). The second lens (304) may include a third surface (314) positioned at the image plane (308) of the first lens and a fourth surface (316) positioned adjacent to the photodetector (146). The second lens (304) may be configured to receive the light output from the first lens (302) and to output light having a second cross-sectional area at the fourth surface (316) that is smaller than the first cross-sectional area.