Abstract
In this paper, we experimentally compared the performance of discrete-Fourier-transform spread (DFT-spread) and pre-equalization in a 244.2-Gb/s polarization-division-multiplexed 16-ary quadrature amplitude-modulation orthogonal frequency-division multiplexing (PDM-16QAM-OFDM) transmission system. The pre-equalization is effective to overcome the high-frequency power attenuation in the channel. However, the acquisition of static channel response for pre-equalization is really complicated and the peak-to-average power ratio (PAPR) of the signal after pre-equalization even becomes a little higher. The DFT-spread can be applied to simultaneously resist high-frequency power attenuation and reduce the PAPR of OFDM signal. The experimental results also show that one band DFT-spread demonstrates the best narrow optical filtering tolerance. The transmission distance for 8 × 244.2-Gb/s wavelength-division-multiplexing (WDM) PDM-16QAM-OFDM at the soft-decision forward-error correction threshold of
$2.4\times 10^{-2}$
is
$2\times 420$
km based on pre-equalization, while extended to over
$3\times 420$
km based on one band DFT-spread, which well illustrates one band DFT-spread is more efficient for high-bandwidth coherent WDM-OFDM system.
© 2014 IEEE
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