Bandwidth improvement of digitized RoF system using track-and-hold amplifier

The implementation of high-frequency digitized RoF system is limited by the insufficient analog bandwidth of the current ADCs. In this paper, we proposed a T/H amplifier assisted scheme, which can relax the high analog bandwidth requirement on ADCs and offer a better SNR. Experimentally demonstration was realized by using a commercial-available T/H amplifier, ADC, clock generator, and FPGA. An OFDM signal at 20-GHz was successfully digitized using an ADC with 4.5-GHz bandwidth, and delivered via a 10-km 8-Gbps digital optical link. BER at 10^-10, 10^-6 and 10^-4 were observed when 4QAM, 8QAM and 16QAM modulation formats were transmitted respectively. A conventional single-tap frequency domain equalizer is used in the receiver for OFDM demodulation, in order to compensate for the uneven frequency response due to the lowpass filter characteristic of the bandpass sampling process.