Rate-adaptive modulation and coding for optical fiber transmission systems
- Modern wireline and wireless communication systems adapt link parameters, such as bandwidth utilization, power allocation, constellation size and forward error correction (FEC) code rate, depending on link quality (often time-varying), trading off bit rate (and thus spectral efficiency) for robustness. By contrast, to date, optical transmission systems have employed fixed bit rates. Rate-adaptive optical transmission techniques trade off information bit rate for transmission distance and other factors affecting signal quality. These techniques enable increased bit rates over shorter links, while enabling transmission over longer links when regeneration is not available. They are likely to become more important with increasing network traffic and a continuing evolution toward optically switched mesh networks, which make signal quality more variable. Rate-adaptive optical transmission could help improve network robustness, flexibility and throughput. This study proposes a rate-adaptive transmission scheme using variable-rate FEC codes and variable-size constellations with a fixed symbol rate. To vary the FEC code rate, we use two different schemes: (a) hard-decision decoding (HDD) using serially concatenated Reed-Solomon (RS) codes and inner repetition codes (b) soft-decision decoding (SDD) using outer RS codes and inner low-density parity-check codes. The FEC schemes are combined with single-carrier polarization-multiplexed quadrature amplitude modulation with variable constellation sizes and digital coherent detection. A rate adaptation algorithm uses the signal-to-noise ratio (SNR) or the bit-error ratio (BER) estimated by a receiver to determine the FEC code rate and constellation size that maximizes the information bit rate while satisfying a target decoded BER and an SNR margin. We simulate single-channel transmission through a long-haul fiber system incorporating numerous optical switches, evaluating the impact of fiber nonlinearity and bandwidth narrowing. In systems with or without inline chromatic dispersion (CD) compensation, we quantify how achievable bit rates vary with distance, and compare the performance of the proposed schemes to an ideal coding scheme. From HDD-based system to SDD-based system, we observed approximately 50% increases in transmission distance, and approximately 2.5-dB reductions in the performance gap from an ideal coding scheme.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Stanford University, Department of Electrical Engineering
|Goldsmith, Andrea, 1964-
|Goldsmith, Andrea, 1964-
|Statement of responsibility
|Submitted to the Department of Electrical Engineering.
|Ph.D. Stanford University 2011
- © 2011 by Gwang-Hyun Gho
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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