DesignCon 2014 Modeling, Extraction and Verification of VCSEL Model for Optical IBIS AMI - White Pap

Keysight Technologies

DesignCon 2014

Modeling, Extraction and Verification of VCSEL Model for Optical IBIS AMI

Abstract

A technique of modeling and extraction of VCSEL devices for IBIS-AMI has been proposed. With the measured L-I and V-I curves of the VCSEL, a behavior model is extracted from rate-equation model that includes thermal effects. Here two suitable curve fitting algorithms are used. This model exhibits the observed performance in both time and frequency domains. It has been verified on several mainstream VCSEL devices where a consistent fitting between the measured data and abstracted one is achieved. And the results prove that the modeling, extraction and verification process can abstract a real VCSEL device accurately. The generation of an IBIS-AMI model facilitates system designs that include VCSEL devices. Also a certain VCSEL can be published into a dynamic link library. This technique is intended to help VCSEL vendors build and publish behavior models with the measured device characteristics. By following the IBIS-AMI standard, VCSEL users can simulate their designs more conveniently.

Authors’

Zhaokai Yuan, Keysight Technologies, Inc.

M. V. Ramana Murty, Avago Technologies, Inc.

Sanjeev Gupta, Avago Technologies, Inc.

Amolak Badesha, Avago Technologies, Inc.

Authors Biographies

Zhaokai Yuan is at Keysight Technologies EEsof division as a R&D system engineer of the SystemVue team. He mainly focuses on Wireless Communication libraries and High Speed Digital libraries developing.

Ramana Murty joined the Fiber Optics III-V Division at Avago Technologies in 2007. He led the development of 850 nm 10G VCSELs for high performance computing and 100 GbE applications. His current interests include the development of VCSELs and p-i-n photodetectors for 25G applications.

Sanjeev Gupta is currently employed by Avago Technology Fiber Optic division as Sr. R&D Manager and is leading a team of Signal Integrity, EMI and Layout engineers. From 1994 to 2011 he was employed by Keysight Technologies and held various application engineering positions. He has co-authored numerous papers and was recipient of DesignCon best paper award consecutively for three years (2008, 2009 and 2010).

Amolak Badesha is Program Director at Avago Technologies, driving strategic initiatives championed by executive management at Fiber Optics Division. Previously, Amolak built and lead the SI/EMI team at Avago’s Fiber Optic Division. Amolak also spent 7 years at Keysight’s EEsof Division, specializing in high-speed design. While at Keysight, Amolak made key contributions to innovative products like Automated AMI model generation and Optical AMI modeling.

I Introduction

The transceiver market has been growing rapidly over the past few years due to the increasing demand of large-scale data communications. An optical link is an effective solution because of high bandwidth and low power consumption.

As illustrated in Figure 1, an optical link consists of Laser Driver, Vertical cavity surface emitting laser (VCSEL), Photo-detector, trans-impedance amplifier (TIA), Limiting Amplifier, optical fiber and clock-data-recovery (CDR). The electrical signal is received from the host board through pluggable or embedded optical module. The received signal goes through signal conditioning to improve signal quality in terms of its amplitude and timing before it is converted to an optical signal. Electrical receiver on the Optical transmitter can utilize various equalization schemes such as Continuous Time Equalizer or De-emphasis before the signal jitter performance is improved using clock and data recovery circuit. Laser driver following receives the signal from CDR output and convert it into a current waveform which drives VCSEL diode. For short range communication, VCSEL provides many advantages such as low power requirements and low cost over other types of electro-optics devices such as DFBs. The output signal from the VCSEL is coupled to a multimode optical fiber using precision optical techniques. On the receiver end, High speed optical signal is received by the p-i-n photo-detector which converts incoming light to a current waveform. The TIA following the p-i-n diode transforms the current waveform into an output voltage waveform. The signal passes through limiting amplifier stages before this data is re-timed and equalized to the host receiver.

In this data link, VCSEL is a key device due to its unique electro-optic characteristics [1] [2] [3]and it is important to model the VCSEL to simulate the performance of an integrated data communication system. Here, a first principles model [4] of a VCSEL is not required. An effective theory in the form of rate equations captures the behavior of the VCSEL [5] [6] [7] [8].

The paper is organized as follows. A rate equation model for the VCSEL including thermal effects is described in section II and the method extracting the model parameters is described in section III. The VCSEL model is applied to three devices from literature in section IV followed by a conclusion.