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arXiv · 2506.04820

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

Keisuke Kawahara·Tai Tsuchizawa·Noritsugu Yamamoto·Yuriko Maegami·Koji Yamada·Shinsuke Hara·Toshihiko Baba
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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.

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Keisuke Kawahara, Tai Tsuchizawa, Noritsugu Yamamoto, Yuriko Maegami, Koji Yamada, Shinsuke Hara, Toshihiko Baba. 2025-06-05. 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. https://doi.org/10.1109/jstqe.2025.3640645

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