Abstract
A prominent technique, for reducing the effect of phase-induced intensity
noise (PIIN) in spectral-amplitude-coding optical code-division multiple-access
(SAC-OCDMA) systems, is proposed. In this technique, each user is assigned
two orthogonal code sequences, selected from a minimum cross-correlation code
set. In addition, two-level <i>M</i>-ary pulse-position modulation (<i>M</i>PPM) scheme is adopted, where each level
corresponds to a code sequence. This technique decreases the effect of PIIN
and allows transmission at high data rates. The bit error rate (BER) of the
proposed system is derived, taking into account the effects of PIIN, shot
noise, and thermal noise. Two performance measures of this system, namely
the BER and maximum achievable number of users, are compared to that of traditional
systems adopting complementary and non-complementary keying. Our results reveal
that the proposed technique allows each user to transmit at high data rates,
compared to traditional techniques, while keeping the BER well below a prescribed
threshold. Finally, our results are extended to higher levels of <i>M</i>PPM schemes with
multicode modulation.
© 2012 IEEE
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