DAC-less PAM-4 generation in the O-band using a silicon Mach-Zehnder modulator

Area of Science:

• Photonics
• Optical Communications
• Semiconductor Devices

Background:

• High-speed optical signal generation is crucial for modern data centers and telecommunication networks.
• Traditional methods often rely on power-intensive digital-to-analog converters (DACs).
• Silicon photonics offers a promising platform for integrated optical modulators.

Purpose of the Study:

• To demonstrate 20-Gb/s 4-level pulse amplitude modulation (PAM-4) signal generation using a silicon Mach-Zehnder modulator (MZM).
• To achieve direct on-chip PAM-4 signal generation, eliminating the need for external DACs.
• To evaluate the performance of the silicon MZM against conventional lithium niobate modulators.

Main Methods:

• Utilizing a silicon Mach-Zehnder modulator (MZM) operating in the O-band.
• Driving the MZM with two independent binary electrical signals.
• Optimizing the amplitude levels of the input binary signals to achieve desired PAM-4 levels.

Main Results:

• Successful generation of a 20-Gb/s PAM-4 signal directly on a silicon chip.
• Achieved a pre-forward error correction (FEC) bit-error rate (BER) as low as 7.6 × 10^-7.
• Demonstrated a performance penalty of only 2 dB compared to a commercial LiNbO₃ modulator at the KP4 FEC threshold.

Conclusions:

• Silicon Mach-Zehnder modulators are capable of efficient, high-speed PAM-4 signal generation.
• On-chip PAM-4 generation using silicon photonics offers a power-efficient alternative to traditional methods.
• The demonstrated silicon MZM shows competitive performance for next-generation optical communication systems.