Simple frequency up-conversion based on nonlinear photodetection scheme of PD in direct modulation radio over fiber system

This paper presents a simple photonic frequency up-conversion system based on direct modulation radio over fiber (RoF) link which employs optical-microwave double-mixing scheme with a high-speed photodetector (PD). With this up-conversion technique, an intermediate frequency (IF) signal of 500 MHz carrying 40 Mbps 16-quadrature-amplitude-modulation (16-QAM) vector signal is up-converted to 16 GHz in a remote antenna unit via 25-km standard single-mode fiber (SMF) transmission. The received 16 GHz radio frequency (RF) signal is demodulated successfully with the error vector magnitude (EVM) of 7.5% rms. The direct modulation up-converting system provides a sufficiently large spurious free dynamic range of 90 dB·Hz2/3. The proposed architecture exhibits the advantages of cost-efficiency, system operation efficiency and reliability.