High-Order Modulation for Asynchronous Optical Data Transport
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Solution Overview
Problem
Existing optical transport systems face challenges with high cost, complexity, and spectral inefficiency when transporting multiple asynchronous data streams, particularly due to limitations in time division multiplexing (TDM) and wavelength division multiplexing (WDM) technologies.
Innovation Solution
The use of high-order modulation techniques, such as phase and amplitude modulation, in conjunction with supplemental multiplexing methods like polarization multiplexing, sub-carrier multiplexing, and time division multiplexing, to efficiently transmit multiple data streams over optical transport systems, maintaining low baud rates for cost-effective optics and electronics while achieving high spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TDM multiplexing is used to transport multiple asynchronous data streams, then the data streams can be synchronized and transmitted over a single optical channel, but the cost, complexity, and power consumption increase due to high-speed electronics and optics requirements
Solution Approach 1:
The patent transitions from traditional TDM's time-domain multiplexing to a hybrid approach that incorporates spatial dimension (polarization multiplexing) and signal constellation dimension (higher-order modulation). By mapping multiple asynchronous data streams to different polarization states and modulation symbols, the system achieves multiplexing without requiring high-speed electronic TDM stages, thereby reducing complexity while maintaining transport capacity.
2Device complexity
If conventional WDM is used to transport lower-speed asynchronous signals, then the system complexity is reduced, but the spectral efficiency becomes very low and full transmission capacity of the fiber is not utilized
Solution Approach 1:
The patent changes the modulation parameters by employing higher-order modulation schemes (e.g., 16-QAM, 64-QAM) instead of conventional binary modulation. This allows multiple bits per symbol to be transmitted, significantly increasing spectral efficiency. Combined with polarization multiplexing, the system achieves high data rate transmission without requiring proportional increases in spectral bandwidth, thus resolving the contradiction between complexity reduction and spectral efficiency.
3Quantity of substance
If higher-order modulation is used to achieve multiple bits per symbol, then spectral efficiency increases, but the system requires more sophisticated modulation and demodulation capabilities
Solution Approach 1:
The patent segments the multiple asynchronous data streams and maps them to different polarization states and modulation symbols in a structured manner. By dividing the data streams into groups that can be independently modulated and by using separate processing paths for different polarization components, the system achieves higher-order modulation with manageable complexity through modular architecture.
Data Source
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AI summary
Aspects of the invention provide transmitters (1102) and receivers (1104) for managing multiple optical signals. High order modulation, such as phase and/or amplitude modulation, is used to achieve multiple bits per symbol by transporting multiple asynchronous data streams in an optical transport system (100). One or more supplemental multiplexing techniques such as time division multiplexing, polarization multiplexing and sub-carrier multiplexing may be used in conjunction with the high order modulation processing. This may be done in various combinations to realize a highly spectrally efficient multi-data stream transport mechanism. The system receives a number of asynchronous signals which are unframed (102) and synchronized (104), and then reframed (106) and tagged (108) prior to the high order modulation (112). Differential encoding (110) may also be performed. Upon reception of the multiplexed optical signal, the receiver circuitry (116) may employ either direct detection without a local oscillator or coherent detection with a local oscillator.