An orthogonal frequency-division multiplexing radio-over-fiber (OFDM-RoF) sy stem based on single sideband (SSB) modulation and direct detection is proposed and simulated.The 10-Gbit/s binary data signal is mapped by quadrat ure amplitude modulation (QAM) and modulated as the baseband OFDM signal which is mixed with the 10GHz radio frequency (RF) clock.The RF OFDM signal then drives the dual-elect rode LiNbO₃Mach-Zehnder modulator (LN-MZM) to generate the optical SSB-OFDM signal which is transmitte d to base station (BS) over standard single-mode fiber (SMF) and broadcast by antenna to user terminals. The simulation results demonstrate that the error vector magnitudes (EVMs) of th e 4QAM- and 16QAM-OFDM s ignals are much below the forward error correction (FEC) limits.Meanwhile,the th eoretical analysis and simulation are preformed to verify that an optimum modulation index exists,which can bring on optimum transmission performance regardless of the fiber length.