Spectrally Efficient Direct-Detected OFDM Transmission Incorporating a Tunable Frequency Gap and an Iterative Detection Techniques

• Published in: Journal of lightwave technology Vol. 27; no. 24; pp. 5723 - 5735
• Main Authors: Peng, Wei-Ren, Zhang, Bo, Feng, Kai-Ming, Wu, Xiaoxia, Willner, Alan E., Chi, Sien
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 15-12-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bandwidth; Carriers; Chromatic dispersion; Circuit properties; Electric, optical and optoelectronic circuits; Electronics; Exact sciences and technology; Frequency division multiplexing; Information, signal and communications theory; Integrated optics. Optical fibers and wave guides; Interference; Iterative methods; Mathematical analysis; Multiplexing; Noise levels; OFDM; Optical and optoelectronic circuits; Optical fiber communications; Optical fibers; optical modulation; Optical noise; Optical sensors; Optical telecommunications; Optical-fiber communication; Orthogonal Frequency Division Multiplexing; orthogonal frequency-division multiplexing (OFDM); Robustness; Sidebands; Signal and communications theory; Signal to noise ratio; Spectra; System performance; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Performance evaluation; Integrated optics; Tunable circuit; Optical links; Chromatic dispersion; Single mode fiber; Iterative method; Spacing; Linear modulation; Signal interference; Optical-fiber communication; Analytical method; Orthogonal frequency division multiplexing; Signal transmission; Optical fiber communication; Robustness; Optical bus; Intensity modulation; Optical modulation; Sideband; orthogonal frequency-division multiplexing (OFDM); Single sideband; Optical fiber; Signal to noise ratio
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2009.2033304

We analytically and experimentally demonstrate a linearly field-modulated, direct-detected virtual single-sideband orthogonal frequency-division multiplexing (VSSB-OFDM) system that employs a tunable frequency gap and an iterative detection technique. The VSSB-OFDM that uses no frequency gap, which is referred to as the gapless VSSB-OFDM, is proposed as a spectrally efficient format. Compared with the intensity-modulated SSB-OFDM, the gapless VSSB-OFDM saves half the electrical bandwidth (BW), and exhibits better receiving sensitivity and more robust tolerance against fiber chromatic dispersion (CD). Furthermore, by incorporating a tunable frequency gap between the optical carrier and the OFDM data sideband, the calculating burden of the iterative detection is greatly alleviated and the system performance can be flexibly improved within moderate iterations. The width of the optimum frequency gap is found to be {\sim} {\hbox {0.35}} sideband BW, which is reached by trading the levels of signal-signal beat interference and the residual image beat interference. Such a gapped VSSB-OFDM system requires fewer iterations to extract the desired data from the interfered signal and exhibits greater robustness against the carrier-to-signal-power ratio (CSPR) variation, compared with the gapless VSSB-OFDM. In this paper, the analytical model of the proposed gapped VSSB-OFDM system will be addressed. In addition, we also successfully conduct a gapped VSSB-OFDM signal transmission over 1600 km of uncompensated standard single-mode fiber (SSMF) with only {\sim} {\hbox {3}} dB optical SNR (OSNR) penalty, and obtain a significant OSNR sensitivity improvement of {\sim} {\hbox {8}} dB, compared with the gapless VSSB-OFDM, after such a 1600-km fiber link.