Optical Serial-to-Parallel Conversion Technique With Phase-Shifted Preamble for Optical Label Switching Systems

We have investigated the fundamental operation of optical serial-to-parallel converter (OSPC) scheme with phase-shifted preamble, and its application to optical label switching operation. The OSPC consists of a π/2 phase-shifted preamble at the top of the packet generated at a transmitter-side, and a -π/2 phase-biased Mach-Zehnder delayed interferometer with the delay length of the timing position of the gated bit followed by a balanced photodetector at a receiver-side. Firstly, we simulated the fundamental performance of the OSPC. The possibility of the serial-to-parallel operation was confirmed. The operation tolerance against the optical phase discrepancy from the ideal conditions, waveguide loss, extinction ratio, and chirp of the input signal were considered. Then, OSPC operation was experimentally investigated. 4-bit operation could be achieved with a suppression ratio of 8 dB in case of the input signal extinction ratio of 13 dB. For the purpose of verifying if the OSPC worked stably and if it could apply to optical label switching systems, packet transfer operation at a bit rate of 40 Gb/s with 2-bit label was also investigated, and we achieved error-free performance successfully for the first time.