Block-wise phase switching for double-sideband direct detected optical OFDM signals.
ABSTRACT We propose phase switching for either main-carrier or subcarriers of two consecutive signal blocks to achieve fading-free double-sideband direct-detection (DD). The proposed approach has twice of the electrical spectral efficiency (SE) of offset OFDM, and the same electrical SE as single-side band (SSB) OFDM. With this scheme, 40-Gb/s DD-OOFDM is successfully received over 80-km SSMF with single polarization and single detector.
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ABSTRACT: An analytical method based on the moment generating function (MGF) is proposed for assessing the performance of direct-detection (DD) orthogonal frequency division multiplexing (OFDM) optical receivers with radio-frequency (RF) demodulation. The MGF-based method is a generalization of the method previously reported in the literature for DD baseband OFDM optical receivers. The proposed method relies on the analytical derivation of equivalent filters that describe the combined effect of electrical filtering + RF demodulation + FFT operation + the equalizer of the OFDM receiver for the real and imaginary parts of the signal at the equalizer output. The method takes into account imperfections of the RF demodulator, namely, power and phase imbalance between the RF demodulator arms and different electrical filtering on its arms. Numerical results show excellent agreement between the bit error probability estimates provided by the proposed method and estimates obtained from Monte Carlo simulation, in the absence and presence of receiver imperfections.Journal of Optical Communications and Networking 02/2014; 6(2):180-189. DOI:10.1364/JOCN.6.000180 · 1.55 Impact Factor
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ABSTRACT: We carry out comprehensive analysis on the fiber nonlinearity impact on the block-wise phase switching (BPS) direct detection (DD) systems. We find that the degenerate four-wave mixing components produced by the interaction between the main carrier and the subcarriers are intrinsically compensated through the direct detection process. For a 100-Gb/s BPS–DD system over 80-km standard single-mode-fiber link, the optimum launch power is found to be 5 dBm, and the optimum carrier-to-signal power ratio is 12 dB. For a single-channel BPS–DD system, the fiber nonlinearity impairment is reduced when low-dispersion fiber is used. However, for a multi-channel BPS–DD system, the nonlinearity noise induced by the crosstalk among the channels is enhanced when the chromatic dispersion of the fiber link decreases.Journal of Lightwave Technology 05/2014; 32(10):1872-1876. DOI:10.1109/JLT.2014.2312999 · 2.86 Impact Factor
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ABSTRACT: In this paper, we propose a novel approach to simultaneously receive multi-band 100-Gb/s direct-detection optical signal with only one polarization and one conventional 40-GHz photodiode. The modulation format of orthogonal frequency-division multiplexing based on offset quadrature amplitude modulation (OFDM/OQAM) is selected to provide signal spectrum with high side-lobe suppression ratio, which can effectively reduce the electrical sub-band frequency interference. The whole 100-Gb/s OFDM/OQAM signal is comprised of 6 sub-bands with 16- and 32-QAM formats loading. Only one guard band is required to accommodate the overlapped 6-band signal-to-signal beat interference (SSBI). The receiver bandwidth is mainly limited by the digital storage oscilloscope (DSO) of 33 GHz. The transmission distance over standard single mode fiber (SSMF) is up to 320 km.Optics Express 05/2014; 22(10):12079-86. DOI:10.1364/OE.22.012079 · 3.53 Impact Factor