All-optical clock recovery from NRZ signal through preprocessing by single narrow-band filter

We demonstrate a simple configuration for clock recovery from nonreturn-to-zero (NRZ) signal, which is preprocessed by a narrow-band filter. Clock component is enhanced evidently after the filter. Compared with previous preprocessing schemes, the single filter is simple and suitable for different bit-rates. The output performances related to the bandwidth and the detuning of the filter are analyzed. By cascading a clock recovery unit with semiconductor optical amplifier based fiber ring laser, clock signal can be extracted from the preprocessed signal with extinction ratio over 10 dB and root mean square timing jitter of 900 fs, at 10 to 40 Gb/s. By simply using a filter with larger bandwidth, much higher bit-rate operation can be achieved easily.