Large-Signal Equivalent Circuit for Datacom VCSELs
Journal article, 2021

Increasing the baud rate in optical interconnects (OIs) will require the use of more sophisticated driver and receiver electronics. This will help overcome the stagnated bandwidth of the Vertical-Cavity Surface-Emitting Laser (VCSEL) and the pin-photodetector. Next generation OIs operating at single lane rates of 50+ Gbaud will therefore require careful co-optimization of the electronics and the optoelectronics. To facilitate this work there is a need of an accurate equivalent circuit for the optoelectronic components, functioning over a broad drive current and ambient temperature range. The VCSEL is the most important and complex to model due to its non-linear behavior and strongly varying characteristics with drive current and ambient temperature. For this purpose, a large-signal equivalent circuit dedicated for high-speed datacom VCSELs has been developed and is presented here. The distributed electrical parasitics in the device layout are carefully considered, the intrinsic speed limitation from carrier transport effects in the Separate-Confinement-Heterostructure (SCH) and the carrier-photon interaction in the Quantum Wells (QWs) are included, and self-heating effects in the device are monitored. The circuit is purposely based on physical instead of empirical models so that it can provide usable feedback to VCSEL designers. For circuit demonstration, it is implemented in Keysight's Advanced Design System (ADS) software and thereafter applied to replicate the performance of a state-of-the-art 28-GHz-bandwidth VCSEL at different temperatures and drive currents. Comparison is made between simulated and measured steady-state characteristics, small-signal behavior, and large-signal response under 28 Gbaud On-Off-Keying (OOK) and Pulse-Amplitude-Modulation 4 (PAM4) modulation, showing good agreement.

Data communication

Equivalent circuits

Temperature distribution



Vertical cavity surface emitting lasers

Integrated circuit modeling

Temperature dependence

Semiconductor lasers

Semiconductor device modeling

Equivalent circuits


Alexander Grabowski

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Johan Gustavsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Zhongxia Simon He

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Anders Larsson

Chalmers, Microtechnology and Nanoscience (MC2), Photonics

Journal of Lightwave Technology

0733-8724 (ISSN) 1558-2213 (eISSN)

Vol. 39 10 3225-3236 9372754

Areas of Advance

Information and Communication Technology


Driving Forces

Sustainable development

Subject Categories


Atom and Molecular Physics and Optics

Communication Systems

Other Electrical Engineering, Electronic Engineering, Information Engineering

Condensed Matter Physics



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