Impact of the extinction ratio on the BER performance in directly detected OFDM systems

The crosstalk induced by considering a non-ideal extinction ratio and its influence on the BER performance in directly detected OFDM are studied in this letter. Also, the finite laser linewidth impairment is considered in the results, and a comparison of both degrading mechanisms is carried out. The results show that a significant reduction of the network capacity may be obtained due to the extra crosstalk level produced by lower extinction ratios in on-off keying (OOK) modulated optical transmissions, even when highly coherent lasers are used.