Real-Time GB-OFDM Signal Generation/ Reception Using Image Spectra and Undersampling for IMDD System.

We proposed and experimentally demonstrated a low-complexity generation and reception scheme for guard-band orthogonal frequency-division multiplexing (GB-OFDM) in intensity-modulation and direct-detection (IMDD) transmission systems. The image spectra that arise in the 2nd Nyquist zone from a digital-to-analog converter (DAC) operating in radio-frequency mode is exploited to efficiently generate GB-OFDM signal. In the receiver, the analog-to-digital converter (ADC) undersampling technique is applied to recover the baseband OFDM signal. The sampling rate of DAC/ADC is reduced and no electrical mixer and oscillators are required for up/down-conversions. Moreover, the same digital signal processing algorithms as the baseband OFDM can be applied to the proposed GB-OFDM. The proposed GB-OFDM scheme is experimentally investigated in a real-time short-reach IMDD system. The results exhibit that the receiver sensitivity in terms of the received optical power of the proposed real-time 16/64QAM-encoded GB-OFDM system over 50 km standard single-mode fiber can be improved by 7.5/3.5 dB at the bit error rate of 3.8e-3, compared to the baseband OFDM. [ABSTRACT FROM AUTHOR]