A novel all-opticalscheme for extracting clock pulses with basic frequency from the receiving non-uniformOTDM optical signal is proposed. The key point is: in the OTDM signal, the space betweentwo pulses is made unequally by artificial means. At the receiver side the base-frequencypulses can be otbained when such signal injects into a mode-locked fiber laser. Thefeasibility of this scheme is proved by experiment.