Optical Network Modulation Selection via Probabilistic Shaping
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Solution Overview
Problem
In digital coherent optical transmission systems, there is a trade-off between baud rate and multilevel modulation scheme, making it difficult to select an optimum combination that balances optical signal to noise ratio (OSNR) tolerance, pass band narrowing, and transmission distance, especially when the degree of multilevel is a positive integer, limiting options and resulting in insufficient transmission distance.
Innovation Solution
A network system that determines a modulation scheme based on degree of multilevel and variable baud rate, calculates bandwidth narrowed by wavelength filters, and selects a combination that maintains predetermined OSNR and quality, allowing for continuous degree of multilevel values using probabilistic shaping, thereby optimizing the selection of baud rate and multilevel modulation scheme.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the degree of multilevel is set to a positive integer value, then the modulation scheme options are limited, but this results in insufficient transmission distance
Solution Approach 1:
The patent changes the parameter of degree of multilevel from discrete positive integer values to continuous values through probabilistic shaping. This allows the degree of multilevel to take any real number value, thereby expanding modulation scheme options while optimizing transmission distance by selecting the precise continuous value that satisfies both bandwidth and OSNR conditions
2Productivity
If the baud rate is increased to achieve higher transmission rates, then the transmission capacity improves, but the bandwidth of the optical signal increases which is narrowed by wavelength filters
Solution Approach 1:
The patent applies parameter changes by introducing continuous degree of multilevel values through probabilistic shaping. This allows optimization of the relationship between baud rate and modulation depth, enabling selection of parameter combinations that achieve high transmission rates while keeping the optical signal bandwidth within the narrowed passband defined by wavelength filters
3Reliability
If the degree of multilevel is increased to reduce baud rate, then the OSNR tolerance improves, but the bandwidth requirement increases which conflicts with pass band narrowing
Solution Approach 1:
The patent uses continuous parameter adjustment through probabilistic shaping to resolve this contradiction. By allowing the degree of multilevel to be any real number, the system can precisely tune the modulation characteristics to achieve adequate OSNR tolerance while simultaneously constraining the bandwidth to fit within the narrowed passband, thus resolving the trade-off between these two parameters
Data Source
AI summary
A network system includes a first device and a second device coupled to the first device. The second device configured to calculate a bandwidth of an optical signal narrowed by a wavelength filter from the number of wavelength filters on a transmission route of the optical signal, to select, based on a plurality of combinations of a degree of multilevel and the baud rate, and a correspondence between a lower limit value of a bandwidth of the optical signal and a lower limit value of an optical signal to noise ratio (OSNR) for maintaining predetermined quality of the optical signal, one or more first combinations from the plurality of combinations, to select a second combination from the one or more first combinations, and to set the degree of multilevel and the baud rate of the second combination in the first device.