Phased-Array Coherent Transceiver for Free Space Optical Links
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Solution Overview
Problem
Atmospheric turbulence significantly degrades the performance of coherent free space optical communications by reducing the coherence of received light, leading to underperformance compared to direct detection systems, and existing adaptive optics solutions are costly, complex, and introduce additional optical losses.
Innovation Solution
A phased-array coherent transceiver system that breaks down the traditional aperture into sub-apertures with single-mode fibers, using phase modulators and a multi-input optical combiner to coherently combine signals, eliminating the need for mechanical actuators and reducing optical losses, and integrating the beam combiner into a photonic integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If adaptive optics systems are used to recover spatial coherence of received light disturbed by atmospheric turbulence, then coherent SNR is improved, but the system becomes costly, complex, and introduces additional optical losses
Solution Approach 1:
The patent divides the traditional single large aperture into multiple sub-apertures (e.g., multiple receive optical elements arranged in an array). Each sub-aperture independently receives optical signals and feeds them to corresponding phase modulators. This segmentation eliminates the need for complex mechanical deformable mirrors while maintaining coherent detection capability through electronic phase control of each segment.
Solution Approach 2:
The patent replaces the mechanical deformable mirror system with electronic phase modulators that directly modulate the phase of optical signals from each sub-aperture. This substitution eliminates mechanical actuators, moving parts, and associated complexity while achieving the same wavefront correction function through electro-optic modulation.
2Measurement precision
If adaptive optics systems are used to recover spatial coherence, then coherent SNR is improved, but additional optical losses are introduced
Solution Approach 1:
The patent extracts the wavefront correction function from the optical path (where it caused losses) and implements it in the electrical domain through phase modulators. By taking out the mechanical correction element from the optical path, the system avoids the optical losses associated with deformable mirrors while maintaining the ability to correct atmospheric turbulence effects.
3Measurement precision
If traditional adaptive optics with deformable mirrors are used, then spatial coherence is recovered, but the system size and weight increase
Solution Approach 1:
The patent replaces heavy mechanical deformable mirror assemblies with lightweight electronic phase modulators and photonic integrated circuits. This substitution dramatically reduces system weight while maintaining the capability to recover spatial coherence through electronic phase control, making the system suitable for applications where weight is critical.
4Measurement precision
If mechanical actuators are used in adaptive optics systems, then wavefront correction is achieved, but reliability decreases due to mechanical failure points
Solution Approach 1:
The patent eliminates mechanical actuators entirely by using electronic phase modulators controlled by electrical signals. This removal of mechanical moving parts eliminates failure modes associated with mechanical wear, actuator breakdown, and alignment drift, significantly improving system reliability while maintaining wavefront correction capability through solid-state electronic control.
5Speed
If phased-array with photonic integrated circuit is used, then bandwidth and speed are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent merges multiple functional components (phase modulators, optical combiners, detectors, and signal processing circuits) into a single photonic integrated circuit. This integration reduces the number of discrete components and their associated alignment requirements, while the high bandwidth of photonic materials enables high-speed coherent detection capable of 40-100 Gbps data rates.
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
The phased-array solution provides higher bandwidth, reduced size, weight, and power consumption, improved signal-to-noise ratio, and easier alignment, resulting in a more robust and efficient coherent communication system with significant space, weight, and power savings compared to adaptive optics systems.
Implementation Method 1
The optical receiver includes multiple phase modulators, each phase modulator processes a phase of an optical signal received from of an RX optical element
Implementation Method 2
The multi-input optical combiner coherently combines first portions of output light signals of the phase modulators
Data Source
AI summary
A phased-array coherent transceiver system includes a transceiver array including multiple receive (RX) optical elements, a number of RX optical fibers, and an optical receiver. The RX optical elements are coupled to the optical receiver via the RX optical fibers. The optical receiver includes multiple phase modulators, each phase modulator processes a phase of an optical signal received from an RX optical element.