A 40-Gb/s PAM-4 Transmitter Based on a Ring-Resonator Optical DAC in 45-nm SOI CMOS

作者：Moazeni Sajjad^*; Lin Sen; Wade Mark; Alloatti Luca; Ram Rajeev J; Popovic Milos; Stojanovic Vladimir

来源：IEEE Journal of Solid-State Circuits, 2017, 52(12): 3503-3516.

DOI：10.1109/JSSC.2017.2748620

• Optical digital-to-analog converter (ODAC)
• optical interconnects
• optical ring resonators
• optoelectronics
• pulse amplitude modulation (PAM)-4 transmitters
• silicon photonics

The next generations of large-scale data-centers and supercomputers demand optical interconnects to migrate to 400G and beyond. Microring modulators in silicon-photonics VLSI chips are promising devices to meet this demand due to their energy efficiency and compatibility with dense wavelength division multiplexed chip-to-chip optical I/O. Higher order pulse amplitude modulation (PAM) schemes can be exploited to mitigate their fundamental energy-bandwidth tradeoff at the system level for high data rates. In this paper, we propose an optical digital-to-analog converter based on a segmented microring resonator, capable of operating at 20 GS/s with improved linearity over conventional optical multi-level generators that can be used in a variety of applications such as optical arbitrary waveform generators and PAM transmitters. Using this technique, we demonstrate a PAM-4 transmitter that directly converts the digital data into optical levels in a commercially available 45-nm SOI CMOS process. We achieved 40-Gb/s PAM-4 transmission at 42-fJ/b modulator and driver energies, and 685-fJ/b total transmitter energy efficiency with an area bandwidth density of 0.67 Tb/s/mm(2). The transmitter incorporates a thermal tuning feedback loop to address the thermal and process variations of microrings' resonance wavelength. This scheme is suitable for system-on-chip applications with a large number of I/O links, such as switches and general-purpose and specialized processors in large-scale computing and storage systems.

• 出版日期2017-12
• 单位MIT