Department of Electrical Engineering, University of Technology, Baghdad, Iraq


orthogonal frequency division multiplexing (OFDM) is emerging as
the leading technology for high data rates. The OFDM based on multicarrier
transmission that transforms a wideband channel into a group of thin-band
channels. The high peak to average power ratio (PAPR) considers the main
drawback factor in this system, so the companding technique modifies the
amplitude of OFDM signal to reduce this factor. The proposed A-law
companding technique has been implemented in intensity modulation/direct
detection optical orthogonal frequency division multiplexing (IM/DDOOFDM).
The proposed companding scheme guarantees the improved
performance in terms of bit error rate (BER) and quality factor (QF) while
reducing PAPR effectively and efficiently by modifying the amplitude of the
transmitted signals. Our results confirm that the suggested scheme exhibits a
good ability to reduce PAPR and a good BER performance based on the use the
A factor. At the complementary cumulative distribution function (CCDF) of 10-
3, the PAPR value of our proposed scheme is about 4.4 dB lower than those of
un-companded signal at best control factor used of A at 87.6, accordingly the
QF is 2.5 dB and the BER is 6.2×10-3 at a distance 900km without any
equalization technique or training sequence or any channel estimation.