Operational Performance of an Optical Serial-to-Parallel Converter Based on a Mach-Zehnder Delay Interferometer and a Phase-Shifted Preamble for DPSK-Formatted Signals
We have investigated the operational performance of an optical serial-to-parallel conversion scheme using a phase-shifted preamble handling optical packets formatted by differential phase shift keying (DPSK) for integrated optical serial-to-parallel converter (OSPC). The same architecture for on-off keyed signals, based on a transmitter-side preamble at the top of the packet and phase-shifted by /2, which is then -/2 phase-biased with a Mach-Zehnder delay interferometer (MZDI), is available for binary and differential PSK signals. The delay length of these signals is determined by the relative timing positions of the gated bit and a balanced receiver-side photodetector. We simulated the operational performance of this scheme and its tolerance against the degree of modulation and optical chirp, with our results showing that a phase shift of more than 0.94 is required in order to attain a suppression ratio in the OSPC output consistent with a bit error rate of less than 10-9 (based on the ratio of intensity of the extracted bit to the maximum peak intensity of the cancelled bits using a single-arm phase modulator). However, by using a Mach-Zehnder phase modulator, the modulation angle can be relaxed to about 0.36. Experimental investigation of the OSPC showed that its functional tolerance with respect to the modulation angle agreed well with the simulated values. Finally, we performed optical label processing using the OSPC in conjunction with an address table, and our results confirmed the potential of the OSPC for use in label recognition.
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