We experimentally assess the bit error rate(BER) performance of an intensity modulation/direct detection(IM/DD) optical orthogonal frequency division multiplexing(OFDM) system based on discrete Hartley transform(DHT) precoding in single-mode fiber(SMF) link for 2.5 Gbit/s quadrature phase shift keying(QPSK) OFDM symbol rate.The experimental results show that for the optical OFDM system based on DHT-precoding,the receiver sensitivity at the BER of 10-4 after 100 km SMF transmission is about 1.5 dBm better than that of the original QPSK OFDM signal,and the DHT-precoded OFDM QPSK signal can achieve approximately 1.3 dB of peak-to-average power ratio(PAPR) reduction.