Monolithic optical PAM-4 transmitter with autonomous carrier tracking

Area of Science:

• Photonics and optical communications
• Integrated photonics
• Semiconductor device physics

Background:

• Micro-ring resonators are key components in integrated photonic circuits.
• Efficient optical transmitters are crucial for high-speed data communication.
• Pulse Amplitude Modulation with 4 levels (PAM-4) enables higher data rates.

Purpose of the Study:

• To present and compare two single-channel optical PAM-4 transmitters.
• To evaluate the performance and energy efficiency of novel micro-ring modulator designs.
• To explore design trade-offs in optical transmitter development.

Main Methods:

• Fabrication of two PN micro-ring modulators in a 90 nm CMOS SOI process.
• Implementation of a 3-section PN-capacitive modulator with on-chip driver and wavelength locking.
• Implementation of a 2-section thermally tuned PN micro-ring modulator with the same driver.

Main Results:

• The 3-section capacitive transmitter achieved 16 Gb/s at 200 fJ/b.
• The 2-section thermal transmitter achieved 22 Gb/s at 430 fJ/b.
• Error-free data rates and energy efficiencies were measured for both designs.

Conclusions:

• The novel 3-section capacitive micro-ring modulator offers superior energy efficiency.
• Design trade-offs between speed and power consumption in optical transmitters are significant.
• CMOS SOI technology is suitable for fabricating advanced optical transmitter components.