Fiber Optic Rotary Joint Thermal Expansion Compensation
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Solution Overview
Problem
Fiber optic collimators with micro lens arrays are prone to thermal degradation due to mechanical tension from temperature changes, leading to signal loss and degradation of optical fibers.
Innovation Solution
A fiber optic rotary joint design featuring a micro lens array with a fiber support system that includes a spacer to maintain fiber length excess, reducing mechanical tension by allowing thermal expansion and contraction without applying force to the lens array, and using a flexible tubular member for additional protection and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the optical fibers are rigidly secured to the micro lens array using epoxy or other fixing materials, then the mechanical stability and positioning precision are improved, but the reliability deteriorates due to mechanical tension and cracks during temperature changes
Solution Approach 1:
The system is divided into two functional segments: a rigid fixation zone at the micro lens array for precise positioning, and a flexible transition zone with excess fiber length for thermal compensation. This segmentation allows each part to perform its specific function without compromising the other.
Solution Approach 2:
The fiber length parameter is deliberately set to be longer than the minimum required distance, creating excess length that can absorb thermal expansion and contraction. This parameter change transforms the fiber from a rigid constraint into a flexible element that maintains optical alignment while accommodating temperature variations.
2Force
If the fiber length is exactly equal to the distance between the lens array and fiber support, then the mechanical tension is minimized under normal conditions, but the reliability worsens during temperature changes due to lack of thermal expansion room
Solution Approach 1:
The excess fiber length acts as a pre-established cushion or buffer zone that absorbs thermal stresses before they can reach the critical fixation points. This beforehand cushioning prevents mechanical tension from developing in the fiber-optic connection during temperature changes.
3Manufacturing precision
If a rigid fiber support structure is used to precisely hold the fibers, then the positioning accuracy is improved, but the reliability deteriorates due to thermal expansion mismatch between different materials
Solution Approach 1:
The excess fiber length serves as an intermediary element between the rigid micro lens array and the rigid fiber support structure. This intermediary absorbs the thermal expansion mismatch stresses, preventing them from being transmitted to the critical alignment interfaces.
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 design ensures the fiber optic rotary joints remain operational across a broad temperature range, minimizing signal loss and preventing mechanical stress on the fibers, thereby enhancing the durability and reliability of the optical transmission system.
Implementation Method 1
With varying temperatures the fibers can expand or shrink without asserting any force to the lens array or the fiber carrier
Data Source
AI summary
A fiber optic rotary joint has at least one fiber optic collimator. The fiber optic collimator has a plurality of lenses on a micro lens array. Furthermore a plurality of optical fibers are attached to the micro lens array. The fibers are further fixed by a fiber support. A spacer is provided between the micro lens array and the fiber support, setting the micro lens array and the fiber support apart from each other. The optical fibers have between the micro lens array and the fiber support a excess length greater than the distance between the micro lens array and the fiber support. This results in a slight bending of the fibers between the micro lens array and the fiber support. A temperature related extension of parts of the fiber optic rotary joint can be compensated by the excess length and does not lead to mechanical tension on the fibers.