Adaptive Coset Coding for High-Rate Plastic Optical Fibre Links
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Solution Overview
Problem
Current techniques for data transmission over plastic optical fibres are limited by high modal dispersion and attenuation, making it difficult to achieve high data rates beyond 100 Mbps without advanced technologies, and existing methods are not efficiently adaptable to changing channel conditions.
Innovation Solution
An adaptive transmission system using three-level coset coding and modulation, which includes selecting suitable BCH codes and modulation schemes based on channel conditions, and employing Tomlinson-Harashima precoding to enhance spectral efficiency and error correction, allowing for flexible configuration of bit partitions and modulation states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional transmission techniques are used over plastic optical fibres, then installation is easy and cost is low, but data rate is limited to around 100 Mbps due to high modal dispersion and attenuation
Solution Approach 1:
The patent changes the modulation format from conventional NRZ to a specialized modulation scheme with optimized symbol rates and constellation points, adapting the transmission parameters to match the POF channel characteristics and overcome modal dispersion limitations
Solution Approach 2:
The patent replaces conventional error correction codes with a specifically designed code structure that is optimized for POF channels, substituting generic solutions with channel-specific coding schemes that achieve better performance at higher data rates
2Speed
If advanced technologies are deployed to achieve high data rates over POF, then data rate increases beyond 100 Mbps, but system complexity and cost increase
Solution Approach 1:
The patent segments the transmission system into distinct functional blocks including specific modulation stages, coded modulation components, and error correction modules, allowing each segment to be optimized independently while maintaining overall system simplicity
Solution Approach 2:
The patent designs a multi-functional transmission system that can adapt to different POF channel conditions and data rate requirements through configurable parameters, making the system universally applicable across various deployment scenarios without requiring multiple specialized systems
3Adaptability or versatility
If fixed transmission schemes are used, then implementation is simple, but adaptability to changing channel conditions is poor
Solution Approach 1:
The patent implements dynamic adaptation mechanisms that allow the transmission system to adjust its parameters based on real-time channel conditions, including variable symbol rates, adaptive modulation formats, and dynamic error correction coding rates to optimize performance under varying POF characteristics
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
The system achieves high spectral efficiency and reliable data transmission at 1 Gbps over plastic optical fibres by adaptively managing channel conditions, overcoming limitations of modal dispersion and attenuation, and enabling flexible bit rate adjustments.
Implementation Method 1
conversion of digital data into an electrical signal for controlling the light emitting element 130. After this conversion of the electric signal to an optical signal
Implementation Method 2
the optical signal from the plastic optical fibre 150 is converted into electrical intensity by means of an opto-electric converter 170 such as a photodiode
Data Source
Figure 1~3
Figure 2A~2B
Figure 4
AI summary
The present invention relates to an efficient coding and modulation system for transmission of digital data over plastic optical fibres. In particular, the digital signal is coded by means of a three-level coset coding. The spectral efficiency of the system is configurable by means of selecting the number of bits to be processed in each of the levels. The first level applies to the digital data a binary BCH coding and performs coset partitioning by means of constellation mapping and lattice transformations. Similarly, second level applies another binary BCH coding, which may be performed selectably in accordance with the desired configuration by two BCH codes with substantially the same coding rate, operating on codewords of different sizes. The third level is uncoded. Both the second and third level undergo mapping and lattice transformation. After an addition of the levels, a second-stage lattice transformation is performed so as to obtain a zero-mean constellation. The symbols output from such three-level coset coder are then further modulated.