Abstract
Recently, the orthogonal frequency division multiplexing (OFDM) technique has been extensively studied
for fiber-based optical transmissions in the context of access networks. The adaptive modulation optical (AMO) OFDM
system has been proved to be one of the cost-effective solutions. Among adaptive modulation techniques, the
Levin–Campello (LC) bit/power loading, which is widely implemented for xDSL systems, is shown to bring excellent
performances in unamplified optical intensity modulated/direct detected (IMDD) transmissions. In this paper a novel
adaptive discrete Fourier transform precoded OFDM (POFDM) is proposed and investigated. By means of numerical
simulation, the proposed modulation scheme is shown to reduce the peak-to-average power ratio of the transmitted OFDM
signal up to 2 dB at 10
$^{-3}$
clipping rate. As a
consequence, a smaller input back-off can be applied to the laser-driving current before the power amplifier,
resulting in a lower power consumption of the POFDM system when compared to the conventional LC AMOOFDM system.
According to simulation results, the energy consumption of the power amplifier is reduced by a factor of two in
unamplified optical IMDD transmissions. Moreover, in terms of capacity-versus-reach performance, the proposed system
achieves the same performance as the conventional adaptive modulation scheme.
© 2014 IEEE
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