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_-4after 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.