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.