Abstract
We investigate discrete Fourier transform-based offset quadrature amplitude modulation (offset-QAM) orthogonal frequency division multiplexing (OFDM) technology. We derive a closed-form expression for the de-multiplexed signal and analyze the influence of crosstalk on implementation algorithms and system performance. It is found that channel estimation in offset-QAM OFDM is different from that in conventional OFDM (C-OFDM) due to the residual crosstalk terms and requires particular study. We propose simple and efficient channel estimation algorithms and show, in a 38-Gbit/s offset-16QAM OFDM experiment with 840-km single-mode fiber, that these algorithms can enable the system performance close to the theoretical limit. By using these algorithms, we compare this technology with C-OFDM and Nyquist FDM (N-FDM) and numerically and experimentally show that DFT-based offset-QAM OFDM can greatly enhance the net data rate for fiber transmissions compared to C-OFDM and exhibit lower complexity than N-FDM. These advantages together with the successfully developed implementation algorithms make this technology very promising for optical communication systems.
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Acknowledgments
This work was supported by the Science Foundation Ireland under Grant Number 11/SIRG/I2124 and 13/TIDA/I2718, and EU \(7\mathrm{th}\) Framework Program under grant agreement 318415 (FOX-C).
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Zhao, J. DFT-based optical offset-QAM OFDM: analytical, numerical, and experimental studies. Photon Netw Commun 31, 294–304 (2016). https://doi.org/10.1007/s11107-015-0545-8
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DOI: https://doi.org/10.1007/s11107-015-0545-8