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All-optical clock recovery from 40-Gb/s nonreturn-to-zero (NRZ) pseudorandom binary sequence data streams based on self-pulsating lasers is presented. A compact preprocessing circuit is utilized to convert an NRZ signal to a pseudoreturn-to-zero sequence before injecting into the optical clock. It comprises a semiconductor optical amplifier followed by a periodical wavelength-division-multiplexing demultiplexer filter. A stable sinusoidal clock signal with a root-mean-square jitter below 700 fs is detected at the output of the self-pulsating laser within data dynamic range of more than 8 dB. The performance of the all-optical clock recovery scheme is investigated by varying the bit rates between 39.81 and 43.02 Gb/s as well as for various wavelengths in the C-band.