Optical Data Transmission With Concatenated FEC and Interleaving
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Solution Overview
Problem
Current data communication systems face challenges in achieving high data rates and low error rates, particularly in optical communication links, due to physical limitations and impairments such as burst errors and phase noise.
Innovation Solution
The implementation of a data transmission method that serially concatenates staircase forward error correction (FEC) with Hamming FEC, combined with multiple interleavers, and the insertion of pilot symbols, to enhance error tolerance and data transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If advanced techniques (e.g., high-order QAM, DSP processing) are used to increase data rate, then bandwidth is improved, but system complexity increases
Solution Approach 1:
The patent segments the forward error correction function into two independent codes: a first FEC code (e.g., staircase code) applied to data blocks, and a second FEC code (e.g., Hamming code) applied to the concatenated result. This segmentation allows each code to be optimized for specific error types without requiring complex unified processing, thereby maintaining high data rates while managing system complexity through modular design
Solution Approach 2:
The patent employs a composite coding structure where two different FEC codes are concatenated together. The first FEC code (staircase) provides robust protection against burst errors, while the second FEC code (Hamming) provides protection against random errors. This composite approach achieves superior error correction performance comparable to complex LDPC codes but with simpler implementation, resolving the contradiction between data rate and system complexity
2Reliability
If single FEC code is used, then device complexity is reduced, but error correction capability deteriorates
Solution Approach 1:
The patent divides the error correction task into two segments: the first FEC code handles burst errors by encoding data blocks independently, while the second FEC code handles residual random errors after the first decoding stage. This segmentation enables each code to specialize in specific error types, achieving comprehensive error correction capability without requiring a single overly complex code structure
Solution Approach 2:
The patent introduces an intermediary processing stage where the output of the first FEC decoder is concatenated with additional data and re-encoded by the second FEC code. This intermediary step allows the system to leverage the strengths of both codes: the burst error protection of the first code and the random error protection of the second code, achieving high reliability without excessive complexity
3Reliability
If interleaving is applied to protect against burst errors, then reliability is improved, but transmission time increases
Solution Approach 1:
The patent segments the error protection mechanism into two parts: the first FEC code provides inherent burst error protection through its coding structure without requiring extensive interleaving, while the second FEC code provides additional protection with minimal interleaving requirements. This segmentation reduces the overall interleaving depth needed compared to traditional single-code systems, thereby reducing processing delay while maintaining reliability
Solution Approach 2:
The patent applies the first FEC encoding as a preliminary action before transmission, which pre-provides burst error protection capability. This preliminary protection reduces the need for aggressive interleaving during transmission, allowing for shorter interleaving depths and reduced processing delay while maintaining the same level of reliability
Data Source
AI summary
The present invention relates to data communication systems and methods thereof. More specifically, embodiments of the present invention provide a data transmission method. Data are encoded with staircase encoder, and staircase coded blocks are first interleaved then combined into outer code frames. Code frames additionally include sync words and padding bits. A second interleaving is applied to the bits of the code frames, and Hamming encoding is performed on the output of the second interleaver. Hamming codewords are Gray-mapped to dual-polarized quadrature-amplitude-modulation (DP-QAM) symbols, and a third interleaving of the symbols from a set of successive Hamming codewords is performed. Pilot symbols are inserted periodically into the stream of DP-QAM symbols. There are other embodiments as well.