A scheme for all-optical repetition rate multiplication of return to zero(RZ) pseudorandom bit sequences(PRBS)is demonstrated with a duty ratio compressor based on terahertz optical asymmetrical demultiplexer(TOAD) cascaded multichannel delay structure．Its feasibility is verified by experiments,which shows that the duty ratio of PRBS is compressed from 50% to 12.5% and than the bit rate is promoted from 2.5 Gb/s to 10 Gb/s with a same code type by the four-channel precise delay．The power penalty for bit error rateless than 10^-9 of the eventual PRBS is 2 dB compared to the original PRBS.