Coherent Detection Device Using Single Photodiode and Polarization Management
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Solution Overview
Problem
Existing optical coherent detection systems in telecommunications face challenges due to signal attenuation and increased complexity and cost caused by the need for multiple photo-detectors and polarization management, particularly in passive optical networks where random polarization variations affect signal coherence.
Innovation Solution
A coherent detection device using a polarization management system with a polarization separator cube and a single photodiode, which separates and aligns optical signals to minimize polarization-dependent losses and reduce the number of photo-detectors required, employing either a 3x1 coupler or integrated optics to focus signals efficiently onto a single photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a 3x3 optical coupler is used to separate oscillation signal into two orthogonal components for polarization-independent detection, then polarization compatibility is improved, but optical signal attenuation increases by approximately 6 dB
Solution Approach 1:
Instead of separating the oscillation signal into two orthogonal components as in prior art, the invention inverts the approach by using a single orthogonal component from the oscillation signal while separating the received signal into two orthogonal components. This inversion allows the use of a 3x1 coupler instead of a 3x3 coupler, reducing optical losses while maintaining polarization-independent detection capability
Solution Approach 2:
The invention extracts only the necessary orthogonal component from the oscillation signal rather than separating both components. By taking out only one component from the oscillation signal and combining it with two separated components from the received signal through a 3x1 coupler, the system achieves polarization independence with reduced optical loss
2Reliability
If three photo-detectors are used to detect the three resulting optical signals from a 3x3 coupler, then detection completeness is improved, but device complexity and wiring requirements increase
Solution Approach 1:
The invention merges the detection function into a single photodiode by combining all three optical signals (two from the separated received signal and one from the oscillation signal) through a 3x1 coupler. This merging eliminates the need for three separate photo-detectors and their associated complex wiring, while the photodiode still captures all signal information through simultaneous illumination
Solution Approach 2:
A single photodiode is made to perform the function of three photo-detectors by receiving and processing multiple optical signals simultaneously. The photodiode detects the combined optical signals from the 3x1 coupler, achieving universal detection capability without requiring multiple specialized detectors
3Reliability
If polarization separator cube and 3x3 coupler are used to ensure coherence between received and oscillation signals, then signal coherence is improved, but production cost increases
Solution Approach 1:
The invention replaces the expensive 3x3 optical coupler with a cheaper 3x1 coupler. By using a less complex and more readily available 3x1 coupler component instead of the specialized 3x3 coupler, the system maintains signal coherence functionality while significantly reducing production costs and manufacturing complexity
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 configuration enhances detection efficiency with reduced optical losses and lower production costs, allowing for more compact and versatile coherent detection systems that maintain signal coherence without the need for complex wiring or multiple detectors.
Implementation Method 1
a polarization management device receiving as input either, in a first case, the optical oscillation signal, or, in a second case, the useful signal, and supplying output two separate signals, on two single-mode optical guides
Implementation Method 2
The advantage in terms of sensitivity compared to direct detection of the signal on a photo-detector is explained by the fact that the power of the electrical signal detected is multiplied by a factor depending on the optical power of the oscillation signal
Implementation Method 3
This multiplication of the optical signals is effective only if the two optical signals are on the same axis of polarization
Data Source
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AI summary
The invention relates to a device for coherently detecting data in an optical signal, called the useful signal (SPL), received over a first single-mode optical fibre (PLSOF), comprising: - a second single-mode optical fibre (LOSOF) that receives an oscillation optical signal (SLO); - a polarization-managing device (DGP) that receives as input either, in a first case, the oscillation optical signal (SLO), or, in a second case, the useful signal (SPL), and that delivers as output two separate signals (SLOV, SLOH), over two single-mode optical guides, the coherently detecting device being configured so that a set of the three signals, which consists of the two separate signals and of either, in the first case, the useful signal (SPL), or, in the second case, the oscillation signal (SLO), is presented to a single photodiode (D).