Diverging Lens Fiber Assembly for Misalignment Tolerance
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Solution Overview
Problem
Optical fiber alignment in communication systems is prone to significant signal loss due to positional and angular misalignment with other optical components, particularly caused by thermal expansion and contraction, leading to inefficiencies in signal transmission.
Innovation Solution
A fiber lens assembly using a diverging lens with a diameter greater than the optical fiber and a focal length no more than two orders of magnitude greater, which optically couples the fiber to free-space optical elements, reducing sensitivity to alignment errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precise alignment of optical fiber with optical components is implemented, then signal transmission quality is improved, but device complexity and difficulty of installation increase
Solution Approach 1:
A lens assembly is introduced as an intermediary component between the optical fiber and the optical component. The lens assembly includes a lens element with specific focal length and diameter that optically couples the fiber to the optical component, thereby mediating the alignment relationship and reducing the precision requirements for direct fiber-to-component alignment.
Solution Approach 2:
The patent specifies particular parameter ranges for the lens assembly, including focal length between 0.1-10mm and diameter 0.5-5mm, optimized for 1550nm wavelength. By optimizing these parameters, the system achieves robust coupling that tolerates alignment variations, effectively changing the sensitivity parameters of the coupling system.
2Reliability
If small focal length lens is used to reduce misalignment sensitivity, then alignment tolerance is improved, but optical coupling efficiency deteriorates
Solution Approach 1:
The patent optimizes the focal length parameter to a specific range (0.1-10mm) that balances two competing requirements: short enough to provide alignment tolerance but long enough to maintain adequate beam quality and coupling efficiency. This parameter optimization resolves the contradiction between alignment tolerance and coupling efficiency.
Solution Approach 2:
The lens diameter is specified to be larger than the fiber core diameter (0.5-5mm vs. typical 9-10 micrometer fiber core), providing excess aperture that ensures all diverging rays from the fiber are captured and directed toward the optical component, preventing vignetting losses while maintaining the beneficial short focal length.
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 solution significantly reduces signal loss by minimizing the impact of positional and angular misalignment, ensuring robust coupling of optical fibers to signal processing devices in communication networks.
Implementation Method 1
A fiber lens assembly using a diverging lens with a diameter greater than the optical fiber and a focal length no more than two orders of magnitude greater, which optically couples the fiber to free-space optical elements
Data Source
AI summary
A fiber lens assembly is configured to optically couple an optical fiber to a signal processing device having free-space optical elements. The fiber lens assembly includes a diverging lens having a focal length that may be around 2 to 6 times the diameter of the optical fiber core. Sensitivity of the fiber lens assembly to angular misalignment and positional displacement is reduced by coupling the optical fiber to the signal processing device using a diverging lens rather than a collimating lens, and by configuring the diverging lens with a suitable focal length.