All-Optical Clock Recovery From NRZ Signals at Different Bit Rates via Preprocessing by an Optical Filter

We demonstrate a simple configuration for clock recovery from a nonreturn-to-zero signal, which is preprocessed by a narrowband filter. Evidently, the clock component is enhanced 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, the clock signal can be extracted from the preprocessed signal, at 10 to 40 Gb/s. By simply using a filter with larger bandwidth, much higher operation can be achieved easily.