ZTE

ZTE Communications ›› 2014, Vol. 12 ›› Issue (4): 40-48.doi: DOI:10.3969/j.issn.1673-5188.2014.04.006

• Research Paper • Previous Articles     Next Articles

Digital Signal Processing for Optical Access Networks

Jianjun Yu   

  1. Optics Labs, ZTE (TX) Inc., NJ 07960, USA
  • Received:2014-10-10 Online:2014-12-25 Published:2014-12-25
  • About author:Jianjun Yu received his PhD degree in electrical engineering from Beijing University of Posts and Telecommunications in 1999. He works for ZTE Corporation as the chief scientist on high - speed optical transmission and director of optics labs in North America. He is also a chair professor at Fudan University and adjunct professor and PhD supervisor at the Georgia Institute of Technology, Beijing University of Posts and Telecommunications, and Hunan University. He has authored more than 100 papers for prestigious journals and conferences. Dr. Yu holds 8 U.S. patents with 30 others pending. He is a fellow of the Optical Society of America. He is editor -in-chief of Recent Patents on Engineering and an associate editor for the Journal of Lightwave Technology and Journal of Optical Communications and Networking. Dr. Yu was a technical committee member at IEEE LEOS from 2005 to 2007 and a technical committee member of OFC from 2009 to 2011.
  • Supported by:
    This work is supported by the High Technology Research and Development Program of China(“ 863”Program) under Grant No. 2012AA011303 and 2013AA010501 and National Nature Science Foundation of China under Grant No. 61325002.

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Abstract: In this paper, we investigate advanced digital signal processing (DSP) at the transmitter and receiver side for signal preequalization and post-equalization in order to improve spectrum efficiency (SE) and transmission distance in an optical access network. A novel DSP scheme for this optical superNyquist filtering 9 Quadrature Amplitude Modulation (9 QAM) like signals based on multi-modulus equalization without post filtering is proposed. This scheme recovers the Nyquist filtered Quadrature Phase-Shift Keying (QPSK) signal to a 9-QAM-like one. With this technique, SE can be increased to 4 b/s/Hz for QPSK signals. A novel digital super-Nyquist signal generation scheme is also proposed to further suppress the Nyquist signal bandwidth and reduce channel crosstalk without the need for optical pre-filtering. Only optical couplers are needed for super-Nyquist wavelength-division-multiplexing (WDM) channel multiplexing. We extend the DSP for short-haul optical transmission networks by using high-order QAMs. We propose a high-speed Carrierless Amplitude/Phase64 QAM (CAP-64 QAM) system using directly modulated laser (DML) based on direct detection and digital equalization. Decision-directed least mean square is used to equalize the CAP-64QAM. Using this scheme, we generate and transmit up to 60 Gbit/s CAP-64QAM over 20 km standard singlemode fiber based on the DML and direct detection. Finally, several key problems are solved for real time orthogonal-frequency-division-multiplexing (OFDM) signal transmission and processing. With coherent detection, up to 100 Gbit/s 16 QAM-OFDM real-time transmission is possible.

Key words: digital signal processing, high spectrum efficiency, super-Nyquist, coherent optical transmission