Frequency-Comb Coherent Receiver for Wavelength-Alignment-Free Subcarriers
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Solution Overview
Problem
Modern optical communication systems face challenges with high power consumption and complex wavelength alignment requirements due to the use of wavelength-dependent receivers, which hinder their deployment in datacenters.
Innovation Solution
An optical data receiver utilizing an optical frequency comb generator as a local oscillator, combined with optical-to-electrical converters and a digital signal processor, performs multi-input multi-output processing to demodulate subcarrier-multiplexed signals without the need for precise wavelength alignment, reducing the complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wavelength-dependent optical receiver with wavelength de-multiplexer and local oscillator laser is used, then coherent detection of WDM channels is achieved, but power consumption increases and wavelength alignment complexity increases
Solution Approach 1:
The optical frequency comb generator serves as a universal local oscillator that can simultaneously support multiple WDM channel detections. Instead of requiring separate LO lasers for each wavelength channel, a single comb generator produces multiple frequency tones that can detect multiple channels, thereby reducing power consumption while maintaining coherent detection capability
Solution Approach 2:
The optical receiver function is segmented into multiple parallel OE converters, each handling a specific frequency passband. This segmentation allows the system to process multiple wavelength channels simultaneously using a shared frequency comb source, reducing the need for multiple complete receiver chains and their associated power consumption
2Reliability
If a wavelength-dependent optical receiver with wavelength de-multiplexer and local oscillator laser is used, then coherent detection of WDM channels is achieved, but device complexity and wavelength alignment requirements increase
Solution Approach 1:
The optical frequency comb generator provides a universal reference that eliminates the need for precise wavelength matching between separate transmitter and receiver lasers. The comb's multiple frequency lines naturally align with WDM channels, simplifying the system architecture by removing wavelength-dependent components like de-multiplexers and reducing alignment complexity
Solution Approach 2:
The system changes the operating parameter from requiring precise wavelength alignment to using frequency tone spacing that matches the WDM channel grid. By controlling the comb generator's frequency spacing to match the WDM channel separation, the system achieves channel alignment through parameter matching rather than physical wavelength stabilization
3Ease of operation
If digital spectral stitching is used to demodulate broad-band optical signal with optical frequency comb, then wavelength alignment requirements are lessened, but signal processing complexity increases
Solution Approach 1:
The broad-band optical signal is segmented into multiple frequency passbands, with each passband processed by a dedicated OE converter. This segmentation allows parallel processing of different spectral portions without requiring complex full-bandwidth processing, reducing the computational burden while maintaining ease of operation
Solution Approach 2:
The patent introduces digital filtering as an intermediary processing step that simplifies the spectral stitching operation. By applying digital filters to isolate and process individual passbands before combining them, the system reduces the complexity of direct spectral stitching while maintaining the benefit of relaxed wavelength alignment requirements
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 enables efficient demodulation of subcarrier-multiplexed signals with reduced power consumption and simplified integration, making it suitable for dense deployment in datacenters and cost-effective applications.
Implementation Method 1
an optical comb generator to output separate frequency tones
Implementation Method 2
Each of the OE converters is configured to mix light of a plurality of the frequency tones with a part of the received optical signal
Data Source
AI summary
An optical data receiver is configured for receiving optical signal comprising spectrally adjacent modulated subcarriers. The optical receiver includes an optical comb generator to output separate frequency tones, and a plurality of optical-to-electrical (OE) converters. The OE converters are configured to mix light of a plurality of the frequency tones with part of the received optical signal, and to output a temporal sequence of measurements of the mixture produced by said mixing. A digital signal processor is configured to recover a data stream carried by one of the subcarriers by performing multi-input multi-output (MIMO) processing using the temporal sequences of measurements output by at least two of the OE converters. The MIMO processing involves performing passband filtering for a passband wherein two of the subcarriers are down-converted by the mixing.