Impact of Optical Power in the Guard-Band Reduction of an Optimized DDO-OFDM System

Abstract

A multiobjective optimization on the parameters of direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems in short-range links is proposed. Based on genetic algorithms, the optimization process takes into account the influence of optical power in the guard-band reduction of such multicarrier systems with 4- and 16-quadratic-amplitude modulation (QAM) subcarrier mapping and for propagation in $40$ km of standard single-mode fiber (SSMF). Simulation results show that the parameters optimization is responsible for a gain of approximately $2.5$ dB [ $\approx 1.8$ dB] in the required optical power for bit-error-rate ${\le }10^{-3}$ , for DDO-OFDM system transmission over $40$ km of uncompensated SSMF, with a guard band $B_G$ equals to $50\%$ of the signal bandwidth $B_w$ and 16-QAM [4-QAM] subcarrier mapping. For an extremely reduced guard band of only $1\%$ of $B_w$ , the gain reduced to $\approx 0.5$ dB and $\approx 1.5$ dB for 16- and 4-QAM mapping, respectively. The optimization process is experimentally validated under the transmission of the optimized DDO-OFDM systems in optical back-to-back (B2B) configuration and $40$ km of uncompensated SSMF. A fair performance comparison is discussed in the experimental results considering $B_G/B_w=0.5$ and $B_G/B_w=0.01$ in the range of the optimized optical powers. It is shown that a maximum optical power penalty of approximately $2$ dBm is registered according to a guard-band reduction from $50\%$ to $1\%$ of the useful bandwidth, for transmission over the 40 km of SSMF, considering 16-QAM subcarrier mapping.