Free-Space Optical Terminal Polarization Routing for Self-Compatible Links
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Solution Overview
Problem
Existing free space optical communication terminals are challenging to design as self-compatible due to differences in uplink and downlink propagation through the atmosphere, particularly in meshed networks where identical terminals are required, necessitating complex terminal switching and different channel configurations.
Innovation Solution
A reconfigurable optical communication terminal uses a combination of wavelength and polarization to distinguish between transmit and receive channels, employing a polarizing beam splitter and quarter-wave plate to switch between circular polarizations, allowing terminals to communicate with identical versions of themselves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different terminals are used at the two sides of the communication link to accommodate uplink and downlink propagation differences, then communication reliability is improved, but device complexity and network configuration complexity increase
Solution Approach 1:
The patent applies parameter changes by switching the operating wavelength between the first wavelength (e.g., 1550nm) and the second wavelength (e.g., 1310nm) based on communication direction. The terminal is configured to transmit at the first wavelength and receive at the second wavelength during uplink, and vice versa during downlink. This wavelength parameter switching allows identical terminals to function as both Tx and Rx devices appropriately, eliminating the need for different terminal types while maintaining communication reliability.
Solution Approach 2:
The patent implements dynamics by making the terminal reconfigurable in real-time. The terminal dynamically switches between transmission and reception modes and corresponding wavelength configurations based on the communication direction and network operational requirements. This dynamic reconfiguration capability allows the same terminal hardware to adapt to different communication roles, reducing the need for multiple specialized terminal types.
2Adaptability or versatility
If wavelength switching is implemented to enable self-compatible terminals, then adaptability is improved, but device complexity increases due to additional switching mechanisms
Solution Approach 1:
The patent applies universality by designing a terminal that can perform both transmission and reception functions at both wavelengths. The same terminal hardware is universally configured to handle uplink and downlink communications by switching wavelengths, eliminating the need for separate specialized terminals. This multi-functional design improves adaptability while the switching mechanism manages the complexity through standardized components.
Solution Approach 2:
The patent uses wavelength switching mechanisms as intermediaries to enable communication between identical terminals. The switching mechanism acts as an intermediary that routes optical signals at different wavelengths to appropriate transmission or reception paths, allowing the terminal to seamlessly transition between different communication modes without requiring fundamentally different hardware configurations.
3Ease of manufacture
If identical terminals are used in meshed networks, then ease of manufacture and deployment are improved, but channel isolation and signal interference become problematic
Solution Approach 1:
The patent applies parameter changes by utilizing different wavelengths (first wavelength and second wavelength) to separate uplink and downlink channels. When identical terminals communicate, one terminal transmits at the first wavelength while the other receives at the second wavelength, and vice versa. This wavelength division provides channel isolation and reduces signal interference, allowing identical terminals to be deployed in meshed networks while maintaining signal integrity.
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
This approach provides a cost-effective and reliable solution for establishing flexible airborne meshed networks by enabling terminals to dynamically switch between transmission and reception modes, improving channel isolation and reducing complexity.
Implementation Method 1
The optical input/output assembly selectively routes the outgoing beam and incoming beam depending on their respective beam polarization
Implementation Method 2
employing a polarizing beam splitter and quarter-wave plate to switch between circular polarizations
Data Source
Figure 1
Figure 2
AI summary
In order to improve free space optical communications, the invention proposes an optical communication terminal (12) that includes a laser source (20), a photo detecting apparatus (22) and an optical input/output assembly (24). These components are controlled by a control logic (26). In order to have the optical communication terminal (12) to be self-compatible, the optical input/output assembly (24) selectively routes the outgoing beam (28) and incoming beam (46) depending on their respective beam polarization. To this end, the optical input/output assembly (24) may include a polarizing beam splitter (36) together with a quarter-wave plate (39).