Two-Channel Multimode Rotary Joint for Bidirectional Transmission
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Solution Overview
Problem
Existing optical rotary joints for bidirectional signal transmission suffer from high costs and significant transmission loss dependent on rotation angle, especially when using single-mode fibers.
Innovation Solution
A rotary joint design featuring a first and second housing part connected by a bearing unit, with light-waveguides aligned along the rotation axis and focusers positioned to minimize beam divergence, allowing for efficient bidirectional signal transmission with reduced construction size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If light is coupled from an inclined light-guiding fiber into another light-guiding fiber disposed on the rotation axis, then bidirectional transmission is achieved, but the attenuation is very large with single-mode fibers
Solution Approach 1:
A beam path is introduced as an intermediary medium to couple light between fibers. The beam path includes optical elements (lenses or mirrors) that facilitate efficient light coupling from the inclined fiber to the fiber on the rotation axis, significantly reducing transmission loss compared to direct coupling
Solution Approach 2:
The optical parameters of the beam path are optimized to match the numerical aperture and mode field diameter of single-mode fibers. By adjusting focal lengths, beam waist positions, and optical element configurations, efficient coupling is achieved despite the angular mismatch between fibers
2Ease of operation
If complex lens systems are used to widen and narrow beam paths for two-channel transmission, then bidirectional communication is enabled, but the device complexity increases and rotational symmetry cannot be achieved
Solution Approach 1:
The optical system is segmented into independent beam paths for different channels. Each channel has its own optimized optical elements, allowing simplified design for each channel while achieving overall bidirectional communication. This segmentation avoids the need for complex integrated lens systems
Solution Approach 2:
The patent accepts and utilizes the asymmetric configuration of fibers (one on axis, one inclined) rather than forcing symmetry. By designing optical elements that specifically accommodate this asymmetric geometry, the system achieves efficient coupling without requiring complex symmetric lens arrangements
3Adaptability or versatility
If elaborate mechanical arrangements with Dove prisms are used for multi-channel transmission, then flexibility and channel capacity increase, but the costs become prohibitively high
Solution Approach 1:
The patent employs simple, inexpensive optical elements such as basic lenses or mirrors instead of expensive precision mechanical components like Dove prisms. These simpler components can be manufactured at low cost while still achieving the required optical functionality for bidirectional transmission
Solution Approach 2:
Complex mechanical arrangements (Dove prisms, rotating mirror systems) are replaced with stationary optical elements. The optical coupling is achieved through carefully designed beam paths with lenses or mirrors, eliminating the need for elaborate mechanical motion and precision alignment mechanisms
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 achieves low transmission loss independent of rotation angle and reduces construction size and cost by using a single focuser per channel and optimizing optical path lengths, enhancing coupling efficiency and compatibility with conventional bus systems.
Implementation Method 1
a first focuser for focusing a light beam emitted by the first light-waveguide onto the end face of the second light-waveguide is provided at the end face of the first light-waveguide
Data Source
AI summary
An optical two-channel rotary joint that is also suitable for coupling of single-mode fibers comprises two housing parts that are rotatable relative to each other. Each of these housing parts accommodates a light-waveguide for supplying light and a light-waveguide for withdrawing light. The arrangement has two optical paths adapted to operate in opposite directions, with each light-waveguide for supplying light being coupled with a light-waveguide for withdrawing light. Furthermore, one focuser is disposed on each of the light-waveguides for supplying light, which focuses the light of the light-waveguide for supplying light onto the corresponding light-waveguide for withdrawing light.