Multi-aperture Optical Receiver for Atmospheric Turbulence
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Solution Overview
Problem
Free-space optical communications from Geostationary Earth Orbit (GEO) satellites to ground stations face significant challenges due to large signal transmission ranges, which require larger telescope apertures, making them susceptible to atmospheric turbulence and costly, while smaller apertures result in lower signal collection efficiency.
Innovation Solution
A multi-aperture free-space optical communications receiver system using multiple telescopes with diameters between 50 mm and 250 mm, each equipped with a wavefront detector and a deformable mirror to correct wavefront distortions, and a coherent combiner unit to align and combine signals for improved signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If larger telescope objective/aperture diameters are used to collect sufficient optical signal from GEO satellites, then signal collection efficiency is improved, but atmospheric turbulence distorts the wavefront and adversely affects coupling efficiency into single-mode optical fibres or phase-matching for demodulation
Solution Approach 1:
The patent divides a large telescope aperture into multiple smaller sub-apertures (e.g., six 100mm apertures instead of one large aperture). Each sub-aperture experiences less wavefront distortion from atmospheric turbulence, allowing coherent detection while maintaining high signal collection efficiency through the combined aperture area.
Solution Approach 2:
The patent transitions from a single large aperture in one dimension to multiple smaller apertures arranged in a two-dimensional array. This spatial distribution allows each sub-aperture to maintain wavefront quality while the collective array provides the necessary collecting area, effectively adding a spatial dimension to the aperture configuration.
2Reliability
If coherent detection is employed to improve signal to noise ratios and transmission data rates, then receiver sensitivity is improved, but the system becomes more susceptible to distorted wavefronts from atmospheric turbulence
Solution Approach 1:
By segmenting the aperture into multiple smaller sub-apertures, each sub-aperture produces a less distorted wavefront that is more suitable for coherent detection. The segmentation reduces the impact of atmospheric turbulence on the coherence requirements of the detection system.
Solution Approach 2:
The patent changes the aperture parameter from a single large diameter to multiple smaller diameters. This parameter change modifies the wavefront characteristics to be more compatible with coherent detection requirements while maintaining the necessary light collection capability through the combined aperture area.
3Quantity of substance
If optical telescopes with apertures larger than about 0.5 metres are used to increase collection efficiency, then signal collection is improved, but the cost increases and complex and expensive adaptive optics are required to mitigate atmospheric effects
Solution Approach 1:
The patent uses multiple moderate-sized telescopes (each with apertures around 100mm) instead of one large telescope (>0.5m). This segmentation achieves the necessary total collecting area without requiring complex adaptive optics systems, as each smaller aperture is less susceptible to atmospheric turbulence effects.
Solution Approach 2:
The patent employs multiple relatively simple, smaller telescopes rather than one complex, expensive large telescope. Each smaller telescope unit is less costly and requires simpler optics, making the overall system more cost-effective despite using multiple units.
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 mitigates atmospheric effects, maintaining signal collection efficiency while enabling coherent detection and higher data rates, reducing the need for complex and expensive adaptive optics systems.
Implementation Method 1
a respective steerable reflector unit including a deformable mirror controllable to deform according to said determined wavefront such that said received light is reflected by the deformable mirror with a modified wavefront
Implementation Method 2
received light is reflected by the deformable mirror with a modified wavefront
Implementation Method 3
a coherent combiner unit arranged to receive a plurality of receiver signals simultaneously from said plurality of optical signal receivers and to coherently combine said plurality of receiver signals to produce a combined signal therewith
Implementation Method 4
a respective optical signal receiver for generating receiver signals in response to received optical signals and comprising an optical fibre wherein the steerable reflector unit is steerable to input said received light with said modified wavefront into said optical fibre for reception by the optical signal receiver
Data Source
AI summary
A multi-aperture free-space optical communications receiver comprises a plurality of telescopes each having a clear objective aperture with a diameter between 50 mm and 250 mm and arranged for receiving light collectively from an optical communications light source. A coherent combiner unit is configured for coherently combining the collectively received light to produce a combined optical signal therewith. Each telescope is arranged in association with, respectively, a wavefront detector to determine a wavefront of said received light directed to it by the respective telescope, a steerable reflector unit including a deformable mirror controllable to deform according to said determined wavefront such that said received light is reflected by the deformable mirror with a modified wavefront, and an optical signal receiver comprising a single-mode optical fibre. The steerable reflector unit is steerable to input received light with modified wavefront into the single-mode optical fibre for reception by the optical signal receiver.