Measurement-based models of a 40 Gbit/s modulator and its electrical driver for transmitter design

Accurate models of the Mach-Zehnder electro-optic modulator and its electrical driver are fundamental for concurrent design of the two devices, and allow careful optimisation of the overall performance of the transmitter. Here a measurement-based 40 Gbit/s model of the two devices is proposed and an implementation using the Agilent-Advanced Design System tool is described. The 40 Gbit/s model of a Mach-Zehnder modulator has been extracted from S-parameters and DC half-wave voltage V_π measurements. The modulator model has been used to re-design a 7 V pp travelling wave driver amplifier previously designed for a standard 50 Ω load. A model of both the original and the re-designed drivers has been extracted to check the performance of the overall transmitter. An improvement of about 6 dB has been obtained for the simulated dynamic extinction ratio with the driver re-designed by using the modulator model: a better eye-diagram is obtained at the output of the transmitter so leading to a signal more robust to attenuation and dispersion within the optical fibre.