A novel 40 Gb/s 3R regenerator was proposed and demonstrated based on two-ring injection mode-locked fiber laser as the clock recovery and electroabsorption modulator as the reshaping optical gate. The effect of the shape of the transmission spectrum of the optical filter on the output pulses of actively mode locked fiber ring laser has been studied experimentally and numerically. It was found that, with the same 3 dB bandwidth, the filter which had a super-Gaussian profile tended to generate narrow pulses. With this scheme, an optical clock pulse train with a spectrum bandwidth of 0.44 nm, a pulse-width of about 6 ps and a timing jitter of <1 ps was recovered. The transmission function of optical gate was improved by optimizing the design of parameters to approach the step function. The width of the switching window was also optimized. With this regenerator, error-free 3R regeneration was performed from 40 Gb/s RZ signal that was degraded by residual dispersion.