Theoretical performance of 10 Gb/s lightwave systems using a III-V semiconductor Mach-Zehnder modulator

The system performance is assessed for 10 Gb/s lightwave systems that use a III-V semiconductor Mach-Zehnder intensity modulator and operate at a wavelength of 1.55 μm with standard single-mode optical fiber. The modulator is modeled by an equivalent circuit and an experimentally derived functional dependence of the attenuation and phase constants on applied voltage. The influence of the format of the modulating signal and the splitting ratio of the input Y-branch waveguide on the chirp characteristics of the modulator is examined based upon calculation of the receiver sensitivity. Optimum system performance is obtained for an asymmetric splitting ratio.