Theoretical and Experimental Investigations of Direct-Detected RF-Tone-Assisted Optical OFDM Systems

• Published in: Journal of lightwave technology Vol. 27; no. 10; pp. 1332 - 1339
• Main Authors: Wei-Ren Peng, Xiaoxia Wu, Arbab, V.R., Kai-Ming Feng, Shamee, B., Christen, L.C., Jeng-Yuan Yang, Willner, A.E., Sien Chi
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 15-05-2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Channels; Chromatic dispersion; Circuit properties; Detection, estimation, filtering, equalization, prediction; Direct detection; Dispersions; Electric, optical and optoelectronic circuits; Electronics; Equalizers; Exact sciences and technology; Filtering; Frequency division multiplexing; Information, signal and communications theory; Integrated optics. Optical fibers and wave guides; Mathematical analysis; Modulation; Multiplexing; OFDM; Optical and optoelectronic circuits; optical fiber communication; Optical filters; Optical modulation; Optical receivers; Optical sensors; Optical transmitters; Orthogonal Frequency Division Multiplexing; orthogonal frequency-division multiplexing (OFDM); Radio frequencies; Radio frequency; RF signals; Signal and communications theory; Signal, noise; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Transmission and modulation (techniques and equipments); Chromatic dispersion; Modulator; Quadrature amplitude modulation; Single mode fiber; Mach Zehnder interferometer; Transmitter; Linear channel; Equalizer; Optical frequency; Radiofrequency; Direct detection; Optical filter; Orthogonal frequency division multiplexing; Optical receiver; Optical fiber communication; Intensity modulation; Optical modulation; orthogonal frequency-division multiplexing (OFDM); Single sideband; High rate transmission
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2008.2012172

In this paper, we propose and experimentally demonstrate a radio frequency (RF)-tone-assisted optical orthogonal frequency-division multiplexing (OFDM) transmission. By inserting an RF tone at the edge of the signal band and biasing the Mach-Zehnder modulator (MZM) at the null point, the proposed system has a better sensitivity and chromatic dispersion (CD) tolerance compared to the previous intensity-modulated single-sideband OFDM (SSB-OFDM). We show analytically that the majority of the linear channel impairments, such as the transmitter, CD, optical filtering, and receiver, can be compensated for by a simple zero-forcing equalizer. Besides, the optimum value of the important parameter, carrier-to-signal-power ratio (CSPR), is analytically obtained and supported via the experimental results. We also observe that the relatively worse sensitivity of the previous SSB-OFDM can be attributed to the limited CSPR. We experimentally demonstrate a 10-Gb/s, 8 quadrature-amplitude modulation (QAM) RF-tone-assisted OFDM transmission, and show that our system has a ~ 5-dB better sensitivity compared to the previous intensity-modulated SSB-OFDM and exhibits a negligible transmission penalty after 260-km uncompensated standard single-mode fiber (SSMF).