Adaptive modulation and intra-symbol frequency-domain averaging scheme for multiband OFDM UWB over fiber system

•An adaptive modulation scheme based on 64/16/4QAM modulation is proposed.•The proposed scheme is experimentally demonstrated in the IM/DD MB-OFDM UWBoF system.•The power penalty of the proposed scheme is about 3.6 dB, compared with 64QAM encoded.•The ISFA algorithm is employed in the MB-OFDM UWBoF system based on the proposed scheme.•The receiver sensitivity has been improved about 0.52 dB by using ISFA algorithm.

To overcome the unbalanced error bit distribution among subcarriers caused by inter-subcarriers mixing interference (ISMI) and frequency selective fading (FSF), an adaptive modulation scheme based on 64/16/4QAM modulation is proposed and experimentally investigated in the intensity-modulation direct-detection (IM/DD) multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) over fiber system. After 50 km standard single mode fiber (SSMF) transmission, at the bit error ratio (BER) of 1×10−3, the experimental results show that the power penalty of the IM/DD MB-OFDM UWBoF system with 64/16/4QAM adaptive modulation scheme is about 3.6 dB, compared to that with the 64QAM modulation scheme. Moreover, the receiver sensitivity has been improved about 0.52 dB when the intra-symbol frequency-domain averaging (ISFA) algorithm is employed in the IM/DD MB-OFDM UWBoF system based on the 64/16/4QAM adaptive modulation scheme. Meanwhile, after 50 km SSMF transmission, there is a negligible power penalty in the adaptively modulated IM/DD MB-OFDM UWBoF system, compared to the optical back-to-back case.