Beacon Multiplexing for FSO Terminal Alignment
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Solution Overview
Problem
High directionality in free space optical (FSO) communications requires accurate and rapid beam pointing between terminals, which is challenging due to environmental factors like strong winds or movement, leading to unpredictable communication links if the FSO beams miss their targets.
Innovation Solution
A local FSO terminal uses multiple beacons with temporally offset pulse trains, where each beacon's pulse rate is equal to the detector's frame rate divided by an integer greater than or equal to two, to avoid pulses falling across frame boundaries, allowing for precise alignment and tracking by identifying the beacon that does not cross frame boundaries and adjusting its orientation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single beacon with pulse rate equal to frame rate is used, then the beacon can be detected at full frame rate, but pulses may fall across frame boundaries reducing modulation depth and detection reliability
Solution Approach 1:
The single beacon is segmented into multiple beacons (at least two), each with pulse trains that are temporally offset relative to each other. This segmentation ensures that at least one beacon's pulses do not fall across frame boundaries, maintaining reliable detection while avoiding the modulation depth reduction problem.
Solution Approach 2:
Multiple beacons transmit periodic pulse trains with different temporal offsets. The periodic nature of the pulse trains, combined with their offset timing, ensures that pulses from at least one beacon consistently align with frame boundaries, providing reliable periodic detection signals.
2Productivity
If multiple beacons with temporally offset pulse trains are used, then alignment speed and sampling rate increase, but device complexity increases
Solution Approach 1:
The alignment function is segmented across multiple beacons, each handling a portion of the temporal sampling. This allows the system to achieve higher effective alignment sampling rates by combining information from multiple beacons with different temporal offsets, improving productivity without requiring a single complex beacon system.
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 increases the misalignment sampling rate, reducing alignment time and enhancing the reliability of FSO communication links by ensuring consistent detection of beacons over background light, even in dynamic environments.
Implementation Method 1
a remote FSO terminal emits a beacon and a local FSO terminal includes a detector. The local terminal senses the beacon
Data Source
AI summary
A local free space optical (FSO) terminal senses an external environment that includes at least two beacons transmitted from a remote FSO terminal. The local terminal is configured to sense the beacons at a frame rate. Each beacon comprises a pulse train with pulses that are transmitted at a pulse rate. The pulse trains are temporally offset relative to each other so that pulses from at least one of the pulse trains do not fall across frame boundaries during sensing, regardless of a temporal location of the frame boundaries. In addition to detecting the at least two beacons, the local terminal is configured to identity the beacon that contains pulses that do not fall across the frame boundaries, and adjust its orientation based on the identified beacon.