Coherent Recombination Device for Multi-Wavelength Beam Phase Alignment
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Solution Overview
Problem
Existing optical communication systems face challenges in maintaining optimal link balance and signal quality due to phase front distortion in free space and multimode fiber propagation, particularly with limitations in adaptive optics speed and noise accumulation in spatial diversity architectures, and restricted spectral band processing in coherent recombination systems.
Innovation Solution
An elementary recombination device with a delay line and variable coupler, along with a phase modulator, compensates for amplitude and phase differences between distorted beams, enabling wide spectral band coherent recombination and optimizing signal reception independently of wavelength, using a Mach-Zehnder interferometer architecture and servo loop for dynamic delay and phase adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phase shifter is used for coherent recombination, then phase alignment is achieved, but spectral bandwidth is limited
Solution Approach 1:
The patent employs dynamic delay lines with variable optical path lengths that can be adjusted in real-time to compensate for wavelength-dependent phase differences. This dynamic adjustment capability allows the system to maintain coherent recombination across multiple wavelengths by adapting the delay compensation to each specific wavelength component.
Solution Approach 2:
The system changes the delay parameter as a function of wavelength, using wavelength-dependent delay compensation. By varying the optical path difference according to the specific wavelength being processed, the system achieves broad spectral compatibility while maintaining precise phase alignment for each wavelength component.
2Reliability
If adaptive optics is used to compensate wavefront distortion, then link budget is optimized, but response speed is limited
Solution Approach 1:
The patent implements pre-compensation of wavefront distortion at the transmitting end using spatial diversity architecture. By preparing multiple independent beam paths in advance with predetermined delay lines, the system eliminates the need for real-time feedback adjustment, thereby achieving fast response to atmospheric turbulence while maintaining link budget optimization.
Solution Approach 2:
The system segments the optical beam into multiple spatial modes or wavelengths that propagate through different atmospheric paths. Each segment is independently processed with its own delay line, allowing parallel compensation of wavefront distortion without requiring a single slow feedback loop, thus achieving both reliability and speed.
3Reliability
If spatial diversity architecture is used, then signal extinction is mitigated, but noise accumulates
Solution Approach 1:
The patent employs feedback control mechanisms that monitor the combined signal from multiple spatial modes and dynamically adjust the delay lines to maximize constructive interference. This feedback optimization ensures that the coherent combination process enhances the signal while minimizing the accumulation of noise, as the system actively controls the interference conditions to favor signal addition over noise addition.
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 allows for broadband, WDM-compatible reception systems with improved signal-to-noise ratio and flexibility across various frequencies, overcoming previous limitations in spectral band processing and noise management, and is suitable for both reception and transmission applications.
Implementation Method 1
a delay line configured to compensate for a time delay between the two elementary beams
Implementation Method 2
a phase modulator configured to adjust a phase difference between the two elementary beams
Implementation Method 3
a variable coupler comprising a first 2x2 combiner, a phase modulator, and a second 2x2 combiner
Implementation Method 4
using a Mach-Zehnder interferometer architecture and servo loop for dynamic delay and phase adjustment
Data Source
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AI summary
The invention relates to an elementary coherent recombination device (15) for a first (F1) and a second elementary beam (F2) comprising: - a first (Input1) and a second (Input2) input into which the first (F1) and second (F2) elementary beams to be recombined are respectively injected, - an output (Out) delivering an output beam corresponding to the coherent recombination of the first and second elementary beams, - a delay line (DL) disposed on one of the paths of said elementary beams and configured to induce a variable delay on said path, - a variable coupler (VC) comprising a first 2x2 combiner (Comb), a phase modulator (PS) and a second 2x2 combiner (Comb'), - a control detector (Det) configured to generate an error signal (ε) from the complementary beam, - a feedback loop (BA) configured to determine, from the error signal,the delay and phase difference to be applied.