Probabilistic Constellation Shaping for Optical Signal Reach
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Solution Overview
Problem
Optical communication networks face limitations in the reach of optical signals due to high noise levels, particularly in superchannels, which restrict data transmission rates and capacity despite advancements in modulation formats like M-QAM.
Innovation Solution
The method involves partitioning M-QAM constellation symbols into two non-overlapping subsets, assigning probabilities based on a target distribution, and selectively transmitting codewords from one subset while refraining from transmitting those from the other subset, using set partitioning and probabilistic shaping to enhance noise tolerance and spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If M-QAM modulation formats are used to increase data transmission capacity, then spectral efficiency is improved, but noise tolerance deteriorates limiting signal reach
Solution Approach 1:
The M-QAM constellation is segmented into two non-overlapping subsets of symbols. By partitioning the constellation, the system can selectively transmit symbols from one subset while refraining from transmitting symbols from the other subset, enabling probabilistic shaping to optimize the balance between spectral efficiency and noise tolerance.
Solution Approach 2:
Different probability distributions are assigned to different symbol subsets based on their local characteristics in the complex plane. Symbols in each subset receive tailored probability assignments that reflect their specific noise tolerance and spectral efficiency characteristics, allowing optimized transmission for each region of the constellation.
2Productivity
If superchannels with tightly packed subcarriers are used to achieve high spectral efficiency, then data capacity is increased, but optical signal-to-noise ratio deteriorates limiting transmission reach
Solution Approach 1:
The system dynamically adjusts the probability distribution of transmitted symbols based on channel conditions and transmission requirements. By making the symbol selection probabilistic rather than deterministic, the system can adapt to varying noise levels and optimize the trade-off between spectral efficiency and signal-to-noise ratio in real-time.
Solution Approach 2:
The invention changes the statistical parameters of the transmitted signal by applying probabilistic shaping to the M-QAM constellation. This transforms the uniform distribution of traditional M-QAM into a non-uniform distribution that optimizes the signal's spectral efficiency while improving its resilience to noise accumulation during transmission.
Data Source
AI summary
Systems and methods for constellation shaping of M-QAM modulation formats in optical transport networks may receive binary data to be transmitted as an optical signal and partition symbols of an M-QAM constellation in the complex plane into two non-overlapping subsets of symbols, The systems and methods may include assigning respective probabilities to each symbol in the first subset of symbols dependent on a target probability distribution for the first subset, mapping at least a portion of the received binary data to the symbols in the first subset, including generating a respective codeword for each symbol in the first subset, in a first symbol period, providing data representing the respective codewords mapped to the symbols in the first subset to an optical modulator for transmission, and refraining from providing any data representing codewords mapped to the symbols in the second subset to the optical modulator until a second symbol period.