High-Bandwidth and Efficient Silicon Microring Modulator Enabling Low-Complexity DMT Transmission

High-speed and energy-efficient optical interconnects are critical for next-generation data center and high-performance computing systems. Silicon microring modulators offer an attractive solution owing to their compact footprint and low power consumption; however, simultaneously achieving large electro-optic bandwidth and high modulation efficiency remains challenging, particularly for low-complexity intensity-modulation and direct-detection links. In this work, we experimentally demonstrate a high-performance silicon microring modulator with an electro-optic modulation bandwidth exceeding 110 GHz and modulation efficiency up to 50 pm/V, enabling high-speed transmission with simplified transmitter and digital signal processing. By employing discrete multi-tone modulation with one-tap frequency-domain equalization, direct-drive transmission from an arbitrary waveform generator is realized without RF amplifiers or bias tees at a data rate of 262.5 Gbit/s below the soft-decision forward error correction threshold using only 0.8 Vpp driving voltage. With electrical amplification, a back-to-back data rate of 300 Gbit/s is further achieved. A comprehensive comparison with single-carrier PAM-4 transmission shows that PAM-4 achieves 260 Gbit/s in a back-to-back configuration using linear equalization, but only 200 Gbit/s over 5 km of standard single-mode fiber with nonlinear equalization due to its sensitivity to chromatic dispersion. In contrast, the DMT-based system maintains robust operation over fiber links up to 5 km with low DSP complexity, achieving 225 Gbit/s. These results represent the highest reported data rate for microring modulator based DMT transmission using linear equalization and demonstrate a scalable, low-power solution for short-reach optical interconnects in future high-capacity silicon photonic systems.