All-optical edge detector for NRZ signal using a SOA-MZI

We propose an all-optical edge detector for the high-speed non-return-to-zero (NRZ) signals by employing a Mach-Zehnder interferometer (MZI) incorporating semiconductor optical amplifiers (SOAs), where the cross phase modulation (XPM) in SOA is exploited. The basic working principle of the proposed edge detector is that the CW probes in the upper and bottom arms always undergo a phase difference of π, except during the leading and tailing transition edges of the NRZ signals. Therefore, the output after the two probes interfering at the constructive port of the MZI will be a series of pulses at only the edges of the NRZ signals. The output signals of the edge detectors are numerically evaluated in terms of the Q factor (>;20dB) and extinction ratio (>;11dB) at 20 and 40 Gb/s, which indicate the high quality of output.