A Low Power CMOS Driver Integrated With Mach-Zehnder Modulator for PAM4 Optical Transmissions

In this paper, we design a wideband driver in 65nm CMOS and integrate with the MZM (Mach-Zehnder Modulator) and bias network to demonstrate high speed electrical-optical (EO) conversion. The driver uses DA (distributed amplifier) topology with stacked-FET cell to achieve more than 23 GHz bandwidth. The issue of breakdown tolerance and bandwidth is much improved by introducing the LPN (low pass network) with stack-FET. Also, the proposed driver adopts a different bias scheme to improve the power efficiency of traditional DA. A transmission efficiency of 15.96 pJ/bit is achieved with a total 734 mW power consumption. The NRZ and PAM4 signals can reach 32 Gb/s and 25 Gbaud/s with more than 5V and 3.8V differential amplitudes respectively by electrical measurements. With integration of MZM, the proposed design demonstrates operating speed of 25Gb/s with 5.41dB extinction ratio (ER) and 23 Gbaud/s with 3.78 ER for NRZ and PAM4 signals, respectively.