A simple AMI-RZ transmitter based on single-arm intensity modulator and optical delay interferometer

In the paper, we propose and demonstrate a simple alternate-mark inversion return-to-zero (AMI-RZ) transmitter upgraded from existing plain RZ-OOK transmitter by employing an additional Mach-Zehnder delay interferometer (MZDI), eliminating the use of high-speed RF circuit and dual-drive Mach-Zehnder modulator. A delay-and-subtract operation is performed by the MZDI on the RZ-OOK signal to achieve alternating phases in successive mark pulses. The nonlinearity tolerance of the generated AMI-RZ signal was characterized by experiment at 10 Gb s−1 and simulation at 40 Gb s−1. The ghost-pulse, due to intra-channel four-wave-mixing (IFWM), with generated AMI-RZ and RZ-OOK formats was also investigated respectively at 40 Gb s−1. The results showed that the generated AMI-RZ exhibited higher nonlinear tolerance over RZ-OOK, especially the tolerance against IFWM in the 40-Gb s−1 optical transmission system. This AMI-RZ transmitter scheme is simple, potentially low cost and can be integrated easily with the existing RZ-OOK transmitters for upgrading to AMI-RZ transmitters.