Free Space Optical Receiver Mode Segmentation
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Solution Overview
Problem
Free space optical communication systems face challenges in maintaining coupling efficiency with single mode fibers due to wave-front distortion and scintillation, leading to reduced transmission rates and data loss.
Innovation Solution
A free space optical receiver and method that separates collected laser light into multiple propagation mode beams based on wave-front fluctuations, guiding each beam through individual single mode transmission media to improve coupling efficiency and transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical coupling with single mode fiber is used to increase bit rate, then transmission capacity is improved, but coupling efficiency deteriorates due to beam spot variation
Solution Approach 1:
The patent divides the single mode fiber into multiple segments (first single mode fiber and second single mode fiber) with different core diameters. The first single mode fiber has a larger core diameter to capture the beam spot and speckle pattern, while the second single mode fiber has a smaller core diameter for efficient coupling. This segmentation allows the system to handle beam variations while maintaining high coupling efficiency.
Solution Approach 2:
The patent introduces a multimode fiber as an intermediary component between the optical antenna and the single mode fibers. The multimode fiber receives the optical signal with the speckle pattern and beam spot variations, then couples it to the first single mode fiber which acts as an intermediate stage before the second single mode fiber. This intermediary structure mitigates the impact of atmospheric disturbances on coupling efficiency.
2Reliability
If fiber bundle with multiple optical fibers is used to prevent coupling efficiency deterioration, then device complexity increases
Solution Approach 1:
Instead of using a complex bundle of multiple single mode fibers, the patent segments a single fiber into multiple sections with different core diameters. This approach achieves the same functional result of handling beam variations while using a simpler single-fiber structure, thereby reducing device complexity.
Solution Approach 2:
Conventional approaches use multiple fibers to handle beam variations. The patent inverts this approach by using a single fiber with varying core diameters along its length, achieving the same effect with reduced complexity. The fiber structure is inverted from a spatial arrangement of multiple fibers to a longitudinal variation within a single fiber.
3Reliability
If large aperture is used to collect optical signal, then tolerance to beam wander increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent segments the optical reception function across multiple fiber sections with different core diameters rather than relying on a single large aperture. The first single mode fiber section with larger core diameter provides the effective aperture for capturing beam wander, while the overall structure maintains manageable manufacturing precision requirements through the gradual transition to smaller core sections.
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
Effectively reduces the deterioration of coupling efficiency and achieves higher transmission rates by controlling propagation modes and using multimode transmission media to mitigate the impact of wave-front distortions.
Implementation Method 1
an optical antenna 10 for collecting the laser light beams 101
Implementation Method 2
an optical fiber 20 for transmitting the optical signal from the optical antenna 10 to the photodetector 30
Implementation Method 3
a photodetector 30 for converting the optical signal into an electrical signal
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
It is impossible to prevent the deterioration of the coupling efficiency between received light and a single mode fiber, and difficult to achieve a higher transmission rate, with respect to a free space optical communication receiver; therefore, a free space optical receiver according to an exemplary aspect of the present invention includes light collecting means for collecting laser light having propagated through a free space transmission path; mode controlling means for separating the laser light collected by the light collecting means into a plurality of propagation mode beams depending on a wave-front fluctuation of the laser light and outputting the propagation mode beams; a plurality of single mode transmission media for guiding the plurality of propagation mode beams, respectively; and a plurality of light receiving means for receiving the plurality of propagation mode beams respectively through the plurality of single mode transmission media.