Silicon photonic (SiP) electro-optic modulators are key component in cost-efficient and integrated optical transmitters. Modulator design traditionally use figure of merits (FOMs) that characterize modulation efficiency and propagation loss of light, which underestimate the modulator-induced power penalty due to intersymbol interference, as they do not consider the electro-optic bandwidth limitation. We show that in presence of limited electrooptic bandwidth of SiP modulator, the conventional FOMs, such as VπL and VπαL, are unable to predict the minimum transmitter power penalty (TPP). Normalized optical modulation amplitude (OMAN) is proved through simulation to be a reliable tool to predict the minimal TPP point. Then, we introduce a new figure of merit that includes not only the efficiency of the modulator, but also the bandwidth limitation from SiP electro-optic modulator. The new FOM that is derived from OMAN, translates the system-level requirements of a PAM-M optical link to the device-level design parameters. This FOM can be hired to optimize driving voltage swing, bias voltage, and phase-shifter length or to simply choose a SiP modulator with minimal imposed TPP.

Co-design and integration of optical modulators and CMOS drivers is crucial for high-speed silicon photonic (SiP) transmitters to reach their full potential for low-cost, low-power electronic-photonic integrated systems. We present a CMOSdriven SiP multi-level optical transmitter implemented using a commercially available lateral p-n junction process. It uses a Mach-Zehnder modulator (MZM) segmented to increase speed and to lower the required power on a per segment basis to a level achievable with CMOS. A multi-channel driver is designed and implemented in 130 nm RF CMOS, providing a swing of 4 V in a push-pull configuration at 20 Gbaud. Binary data at the CMOS input is manipulated via digital logic to produce the proper persegment drive signals to generate a four-level pulse-amplitude modulation optical signal. Multi-level modulation is achieved using only binary signals as input (DAC-less). Co-simulation of the optical and electrical circuits shows good agreement with experiment. Reliable transmission is achieved without postcompensation at 28 Gb/s, and at 38 Gb/s when using postcompensation.

We theoretically study the performance of single sideband discrete multi-tone (SSB-DMT) in the C-band with intensity modulation and direct detection (IMDD). Our analysis allows us to quantify the impact of different noise sources such as signal-to-signal beating interference, phase-to-amplitude noise, attenuation, and receiver sensitivity on SSB-DMT. Our analytical tools also allow us to optimize the signal-to-carrier power ratio to maximize SSB-DMT throughput. We provide equations to calculate bit error rate of bit allocated SSB-DMT. Finally we examine various system parameters (laser linewidth, system bandwidth, and fiber length) to determine their impact on the performance of zero guard band SSB-DMT.

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