High-efficiency compact optical transmitter with a total bit energy of 0.78 pJ/bit including silicon slow-light modulator and open-collector current-mode driver

TL;DR

This paper introduces a highly efficient, compact optical transmitter combining a silicon slow-light photonic crystal waveguide modulator and an open-collector current-mode driver, achieving ultra-low bit energy suitable for large-scale datacenter interconnects.

Contribution

It presents a novel integrated transmitter design with a photonic crystal waveguide modulator and optimized driver, significantly reducing power consumption and footprint for high-speed optical communication.

Findings

Bit energy of 0.78 pJ/bit at 64-Gbaud

Power consumption reduced to 50 mW

Footprint minimized to 0.66 mm²

Abstract

Increasing datacenter demands require power-efficient optical interconnects. However, a conventional standard transmitter using a silicon rib-waveguide Mach-Zehnder modulator and voltage-mode driver has low efficiency and consumes watt-class high power and occupies a several-square-millimeter footprint, which limits large-scale integration for parallel transmission. This paper presents a transmitter consisting of a compact photonic crystal waveguide (PCW) modulator and a current-mode open-collector driver. The PCW modulator is designed to have high impedance in addition to the slow-light effect. The driver connected to the modulator without termination resistors is optimized based on electronics-photonics co-simulations using a standard electronic circuit simulator with an in-house photonic model library. Co-packaging these dramatically reduces the power consumption to 50 mW and a bit energy to 0.78 pJ/bit at 64-Gbaud, and the footprint to 0.66 mm2. This result represents a significant advancement toward the integration of a large number of transmission channels with no temperature control.