A novel symbol overlapping optical fast frequency-hop code-division multiple access (FFH-OCDMA) system is proposed, and its bit error rate (BER) performance is investigated under consideration of avalanche photonic diode (APD) noise and thermal noise. An experimental symbol overlapping (SO) FFH-OCDMA testbed is developed and some experimental results are given. The theoretical and experimental results show that the system is apt to implement and has larger throughput.