Joint timing and frequency synchronization in coherent optical OFDM systems
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In this paper, we review our joint timing and frequency synchronization algorithms in coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. We first present a timing estimation method by designing the pattern of the training symbol, whose timing metric has a sharp and clear peak, to ensure accurate timing offset (TO) estimation performance. Then we provide both data-aided (DA) and blind (BL) approaches to estimate the carrier frequency offset (CFO). For the DA algorithm, we utilize the same training symbol structure as the timing estimation does, while for the BL algorithm, we utilize the zero-subcarrier power (ZSP) to achieve full-range CFO estimation. Note that our joint timing and frequency synchronization approaches require only one OFDM symbol, which ensure not only the data transmission efficiency, but also the TO and CFO estimation performance. A modified BL ZSP algorithm is proposed to further improve the CFO estimation performance by taking the power average over a series of OFDM symbols. The effectiveness of the TO estimation algorithm, and both the DA and BL CFO estimation algorithms are verified and demonstrated in both simulations and experiments.
Keywordstiming offset (TO) carrier frequency offset (CFO) coherent optical orthogonal frequency division multiplexing (CO-OFDM) zero-subcarrier power (ZSP)
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The authors would like to thank the supports of Grants 61501313, 61571316 and 61302112 from NSFC and Grant 1-ZE5K from the Hong Kong Polytechnic University.
- 1.Shieh W, Djordjevic I. OFDM for Optical Communications. Burlington: Academic Press, 2009Google Scholar
- 3.Hara S, Prasad R. Multicarrier Techniques for 4G Mobile Communiations. Norwood, MA: Artech House, 2003Google Scholar
- 11.Du X, Zhang J, Xu Z, Yu C. A novel timing estimation method for coherent optical OFDM systems. In: Proceedings of Asia Communications and Photonics Conference. Optical Society of America, 2015, paper AS4F. 5Google Scholar
- 13.Cao S, Zhang S, Yu C, Kam P Y. Full-range pilot-assisted frequency offset estimation for OFDM systems. In: Proceedings of Optical Fiber Communication Conference/National Fiber Optic Engineers Conference. Optical Society of America, 2013, paper JW2A. 53Google Scholar
- 15.Wu J, Tang M, Xu L, Zhu S, Cheng J, Feng Z, Zhang L, Wang X, Lin R, Deng L, Fu S, Shum P P, Liu D. A robust and efficient frequency offset correction algorithm with experimental verification for coherent optical OFDM system. Journal of Lightwave Technology, 2015, 33(18): 3801–3807CrossRefGoogle Scholar
- 18.Du X, Zhang J, Yu C, Kam P Y. Blind carrier frequency offset estimation for coherent optical OFDM systems. In: Proceedings of Advanced Photonics (IPR, NOMA, Sensors, Networks, SPPCom, SOF). Optical Society of America, 2016, paper SpW2G.3Google Scholar