Experimental Analysis of 8-QAM Constellations for Adaptive Optical OFDM Systems

In this letter, we numerically and experimentally evaluate the influence of adopting different 8-QAM constellations. The performance of flexible/adaptive direct detection optical orthogonal frequency division multiplexing transmission systems has been evaluated in the back-to-back configuration. Metro/regional network scenario is also considered using the four-node photonic mesh network of the ADRENALINE testbed. In general, different optical paths of the network ranging from 50 to 185 km are analyzed to asses the optimal 8-QAM format, which maximizes the system performance. In addition, single side band modulation is implemented in order to enhance the robustness against the chromatic dispersion (CD). The effect of CD on the format selection is investigated targeting different data rates using the implemented loading algorithm.