Improved dispersion tolerance of an optical duobinary transmitter based on a Mach–Zehnder modulator and an optical delay interferometer

We present a method for improving the dispersion tolerance of an optical duobinary transmitter based on a dual-arm Mach–Zehnder (MZ) modulator and an optical delay interferometer without electrical low-pass filters. Since such a duobinary modulator using a standard 1-bit delay cannot provide high dispersion tolerance, we investigated the impact of the modulator driving voltages and the bit delay in the interferometer to improve the transmitter’s dispersion tolerance.