Abstract
In this paper, we provide a numerical bit error rate (BER) estimation
approach for direct-detected orthogonal frequency division multiplexing (OFDM)
signals in the presence of optical preamplified receivers. The individual
BER of each subcarrier is first computed by considering their electrical signal-to-noise
ratio (SNR), and then the ensemble BER is derived simply by taking the average
of all the subcarriers' BERs. The calculated BER is verified by the conventional
error-counting approach with high precision and is still accurate with higher
quadratic-amplitude modulation (QAM) formats, even under the influences of
the optical filtering and polarization mode dispersion (PMD) effects. Based
on our simulation approach, the required extra power budget for 16- and 64-QAM
relative to 4-QAM format are found to be ${\sim}$3.8 and 8.2 dB, respectively, at a
BER of 10$^{-9}$.
Furthermore, we use this approach to compare the receiving sensitivities and
PMD tolerances for the previous proposed gapped and interleaved radio-frequency
(RF)-tone-assisted OFDM systems. The results show that the gapped OFDM has
a better sensitivity while the interleaved OFDM has a more PMD-tolerable capability.
© 2008 IEEE
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