Single-Fiber Bidirectional Optical CAN Bus for Aircraft Weight Reduction
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Solution Overview
Problem
Current electrical CAN bus assemblies in aircraft have issues such as time-consuming assembly, susceptibility to electromagnetic effects, impedance mismatch, and single-point failures, which lead to increased weight, size, and maintenance costs.
Innovation Solution
Conversion of electrical CAN bus to a passive optical CAN bus using a single fiber for both transmit and receive, a single wavelength, and a passive reflective optical star with high-isolation optical Y-couplers, reducing weight and labor in manufacturing and installation while minimizing bus configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical CAN bus assemblies are used to connect LRUs, then data transmission between electrical components is achieved, but the weight and size of connections become burdensome
Solution Approach 1:
The patent replaces the electrical CAN bus system with an optical CAN bus system using plastic optical fibers (POF) instead of copper wiring. This substitution eliminates electromagnetic interference while achieving the same data transmission function, resolving the contradiction between reliable data transmission and excessive weight/size of electrical connections
2Adaptability or versatility
If T-couplers are assembled in electrical CAN bus, then multiple LRUs can be connected, but assembly becomes time-consuming due to lifting and reconnecting double shields
Solution Approach 1:
The patent segments the electrical T-coupler assembly into separate functional components: the optical Y-coupler handles signal distribution while the double shields remain attached to the cable assembly. This segmentation allows the shields to stay connected throughout assembly, eliminating the time-consuming lifting and reconnecting operations while maintaining the ability to connect multiple LRUs
3Reliability
If electrical CAN bus is used, then LRUs can communicate, but the system is susceptible to electro-magnetic effects
Solution Approach 1:
The patent substitutes electrical signal transmission with optical signal transmission using plastic optical fibers. This replacement eliminates the susceptibility to electromagnetic effects while maintaining reliable communication between LRUs, as optical signals are inherently immune to electromagnetic interference
4Manufacturing precision
If critical stub lengths are specified from T-coupler to LRU, then impedance matching is achieved, but reuse of bus assembly for different CAN bus configurations is prevented
Solution Approach 1:
The patent designs the optical bus assembly with universal connectors and standardized interfaces that allow the same physical assembly to be reused across different CAN bus configurations and node quantities. The optical system eliminates the strict stub length constraints of electrical systems, enabling a single bus assembly design to serve multiple application scenarios
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 optical CAN bus solution reduces weight and labor in manufacturing and installation, enhances performance by eliminating single-point failures and electromagnetic interference, and provides flexible operation independent of bus speed and distance.
Implementation Method 1
optical networking using plastic optical fibers can provide advantages over networking using copper or other metal wiring
Implementation Method 2
The fiber optical network uses a single fiber and a single wavelength for transmit and receive, and comprises a passive reflective optical star, which receives broadcast optical pulses and reflects them back toward all CAN nodes. The reflective optical star comprises an optical mixing rod having a mirror at one end.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A controller area network (CAN) comprising a plurality of CAN nodes that communicate via a CAN bus that comprises a fiber optical network. The fiber optical network uses a single fiber and a single wavelength for transmit and receive, and comprises a passive reflective optical star. The reflective optical star comprises an optical mixing rod having a mirror at one end. The other end of the reflective optical star is optically coupled to the transmitters and receivers of a plurality of optical-electrical media converters by way of respective high-isolation optical Y-couplers. Each CAN node produces electrical signals (in accordance with the CAN message-based protocol) which are converted into optical pulses that are broadcast to the fiber optical network. Those optical pulses are then reflected back to all CAN nodes by the reflective optical star.