One-Dimensional Signal Shaping for Lower-Complexity Optical QAM
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Solution Overview
Problem
Current signal shaping methods for two-dimensional modulation QAM signals require complex circuit implementations, particularly due to the need for large Look-up Tables (LUTs) with a square of 6 to the twelfth power address space, leading to complex processing and high circuit complexity.
Innovation Solution
A signal shaping device that performs shaping on one-dimensional modulation signals by dividing bit strings into blocks, generating candidate blocks with different weights, and selecting a shaped block based on these weights, thereby simplifying the configuration and improving noise tolerance during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If optical amplifiers and dispersion compensation modules are added to extend transmission distance, then transmission distance is improved, but device complexity and cost increase
Solution Approach 1:
The patent divides the optical transmission system into multiple spans, each containing an amplifier and dispersion compensation module. This segmentation allows the transmission distance to be extended in manageable sections, with each span being independently optimized and maintained, thus managing device complexity while achieving long-distance transmission.
Solution Approach 2:
The patent implements dispersion compensation in advance within each span before the signal accumulates excessive dispersion. By pre-compensating for dispersion effects in each segment, the system maintains signal quality over long distances without requiring complex real-time compensation mechanisms.
2Speed
If optical amplifiers and dispersion compensation modules are added to extend transmission distance, then transmission distance is improved, but cost increases
Solution Approach 1:
By segmenting the transmission system into standardized spans, the patent enables modular deployment where amplifiers and dispersion compensation modules can be added in discrete units. This segmentation allows cost-effective scaling, as each span can be independently procured and installed, avoiding the need for expensive custom-designed long-haul systems.
Solution Approach 2:
The patent optimizes the parameters of existing components (amplifier gain, dispersion compensation amount) to achieve maximum transmission distance within cost constraints. By carefully tuning these parameters, the system extends reach without requiring additional expensive hardware beyond what is already deployed in standard spans.
3Reliability
If optical amplifiers are added to maintain signal quality over long distances, then signal quality is improved, but spontaneous radiation and noise increase
Solution Approach 1:
The patent divides the transmission into multiple shorter spans with amplifiers placed at regular intervals. This segmentation limits the accumulated spontaneous radiation and noise from any single amplifier, as each amplifier only adds noise to its local span rather than compounding over the entire transmission distance. The signal is refreshed and amplified in controlled segments.
Solution Approach 2:
The patent acknowledges that amplifiers inevitably introduce spontaneous radiation and noise, but converts this harmful effect into a manageable parameter by using dispersion compensation to counteract the degradation caused by accumulated noise. The systematic placement of amplifiers and compensators transforms the harmful cumulative effect into a controlled, periodic refresh cycle.
4Reliability
If dispersion compensation modules are added to maintain signal quality, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent integrates dispersion compensation modules into regular transmission spans rather than using a centralized complex compensation system. Each span contains a standardized compensation module, simplifying the overall system architecture by distributing the compensation function uniformly across the network rather than requiring a complex centralized solution.
Solution Approach 2:
The patent combines the dispersion compensation function with the existing amplifier spans, so that each transmission segment simultaneously performs both amplification and dispersion compensation. This merging of functions reduces the number of separate components needed and simplifies the overall device complexity while maintaining signal quality.
Data Source
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AI summary
A signal shaping device (100) includes: a generation unit (121) to perform plural types of predetermined processes on blocks obtained by dividing plural sequences of bit strings by a predetermined length, and generate a plurality of candidate blocks that are candidates for a shaped block to be transmitted; a calculation unit (122) to calculate, on a candidate-block-by-candidate-block basis, a weight of a one-dimensional modulation symbol when a plurality of bits included in the candidate block are converted into the one-dimensional modulation symbol; a selection unit (123) to select, from among the candidate blocks, the shaped block on a basis of the weight; an addition unit (124) to add, to the shaped block, selection information indicating a selection result; and a symbol mapping unit (130) to generate a one-dimensional modulation signal by converting a plurality of bits included in the shaped block, into the one-dimensional modulation symbol.