Chromatic Risley Prism Pair for FSO Beam Separation
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Solution Overview
Problem
Free space optical communication terminals face challenges in accurately maintaining directional alignment between transmit and receive beams, which is crucial for establishing and sustaining a viable link, especially in scenarios where physical connections are impractical.
Innovation Solution
Incorporating a chromatic Risley prism pair along the optical paths of both transmit and receive beams, which creates an adjustable angular separation due to wavelength dependence, allowing for precise control of beam directions using a controller that can also adjust the wavelength of the transmit beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If accurate pointing between terminals is required to establish and maintain a viable FSO link, then communication reliability is improved, but device complexity increases due to the need for separate pointing and tracking mechanisms
Solution Approach 1:
The patent combines the pointing and tracking functions into a single integrated system by using a chromatic Risley prism pair that simultaneously controls both transmit and receive beam directions. The prism pair creates angular separation between co-propagating beams of different wavelengths, allowing one optical component to perform what traditionally required separate mechanisms.
Solution Approach 2:
The chromatic Risley prism pair serves multiple functions: it acts as both a beam steering device and a beam separation device. By exploiting chromatic dispersion, the same optical component directs transmit and receive beams along different angular paths while maintaining accurate pointing, thereby reducing the need for additional dedicated components.
2Object-affected harmful factors
If transmitted beams and received beams propagate along different directions, then communication privacy is improved, but pointing accuracy becomes more difficult to maintain
Solution Approach 1:
The patent changes the directional parameter of the optical beams by using a chromatic Risley prism pair that introduces wavelength-dependent angular separation. This allows the transmit and receive beams to propagate along different directions for privacy while the controller maintains precise angular control through adjustable prism configurations.
Solution Approach 2:
The patent replaces traditional mechanical beam steering mechanisms with a chromatic optical system. Instead of using separate mechanical actuators to physically redirect beams, the system uses the chromatic dispersion properties of the Risley prism pair to naturally separate beam paths based on wavelength, reducing mechanical complexity while maintaining directional control.
3Ease of operation
If chromatic Risley prism pair is used to create angular separation between beams, then beam direction control is improved, but device complexity increases
Solution Approach 1:
The patent exploits the chromatic dispersion parameter of optical materials to achieve beam separation. By selecting prism materials with specific dispersion characteristics and adjusting the prism angles, the system creates controllable angular separation between wavelengths, providing easy beam direction control through parameter adjustment rather than complex mechanical reconfiguration.
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 solution enables precise angular separation and adjustment of beam directions, enhancing the reliability and efficiency of free space optical communication links by ensuring accurate pointing and reducing the need for separate pointing and tracking mechanisms, thus improving communication capacity and privacy.
Implementation Method 1
the chromatic Risley prism pair creates an angular separation between the Rx and Tx optical beams
Implementation Method 2
Since the Rx and Tx optical beams have different wavelengths and the chromatic Risley prism pair has a wavelength dependence
Data Source
AI summary
Embodiments relate to a free space optical (FSO) terminal that transmits and receives (e.g., data-encoded) optical beams. The FSO terminal includes a fore optic (e.g., telescope) and a chromatic Risley prism pair. A receive (Rx) optical beam is received through the fore optic, and a transmit (Tx) optical beam is transmitted through the fore optic. The chromatic Risley prism pair is positioned along the optical paths of both the Rx and Tx optical beams. Since the Rx and Tx optical beams have different wavelengths and the chromatic Risley prism pair has a wavelength dependence, the chromatic Risley prism pair creates an angular separation between the Rx and Tx optical beams. A controller controls the Risley prism pair (and possibly also the wavelength of the Tx optical beam) to achieve a desired angular separation between the Rx and Tx optical beams in free space.