High-Linearity PAM-4 Silicon Micro-ring Transmitter Architecture with Electronic-Photonic Hybrid DAC

TL;DR

This paper introduces a novel high-linearity PAM-4 silicon micro-ring transmitter architecture with a three-segment modulator and adjustable driver, enhancing linearity, wavelength tunability, and insertion loss control for high-performance optical communication.

Contribution

The paper proposes a three-segment micro-ring modulator with an adjustable driver circuit, enabling improved linearity and tunability in PAM-4 optical transmitters, which is a novel approach compared to traditional designs.

Findings

Achieves approximately 0.037 nm wavelength tunability.

Provides an adjustable insertion loss of about 2 dB.

Enhances PAM-4 linearity and output control.

Abstract

This paper presents a high linearity PAM-4 transmitter (TX) architecture, consisting of a three-segment micro-ring modulator (MRM) and a matched CMOS driver. This architecture can drive a high-linearity 4-level pulse amplitude (PAM-4) modulation signal, thereby extending the tunable operating wavelength range for achieving linear PAM-4 output. We use the three-segment MRM to increase design flexibility so that the linearity of PAM-4 output can be optimized with another degree of freedom. Each phase shift region is directly driven by the independently amplitude-tunable Non-Return-to-Zero (NRZ) signal. The three-segment modulator can achieve an adjustable wavelength range of approximately 0.037 nm within the high linearity PAM-4 output limit when the driving voltage varies from 1.5 V to 3 V, simultaneously achieving an adjustable insertion loss (IL) range of approximately 2 dB, roughly four times that of the two-segment MRM with a similar design. The driver circuit with adjustable driving voltage is co-designed to adjust the eye height to improve PAM-4 linearity. In this article, the high linearity PAM-4 silicon micro-ring architecture can be employed in optical transmitters to adjust PAM-4 eye-opening size and maximize the PAM-4 output linearity, thus offering the potential for high-performance and low-power overhead transmitters.