Experiment on 2.5 Gbit/s symbol overlapping fast frequency-hopping optical code division multiple access (SO-FFH OCDMA) system with single user is designed and demonstrated. Under user′s data rate 2.5 Gbit/s, fiber Bragg grating based optical encoder and decoder are designed and fabricated employing one-coincidence sequence, which the number of wavelengths is seven and code length is four. The spectra of optical encoder and decoder are measured. Pulse generator generates 2.5 Gbit/s non-return zero (NRZ) pulse signal, which is used to externally modulate amplified spontaneous emission (ASE) broadband source, and then optical signal is fed into optical encoder to spread spectrum. At the receiver, an Erbium-doped fiber amplifier (EDFA) is employed to amplify the encoded optical signal, then optical signal is fed into the decoder, and is also converted into electrical signal by 2.5 Gbit/s receiver module. It can be shown from the waveforms of decoded optical signal and the electronic signal that, user′s data can be decoded correctly at 2.5 Gbit/s data rate. Experiment shows that compared with traditional FFH OCDMA, SO-FFH OCDMA has much higher user′s data rate.