100 Gbaud On–Off Keying/Pulse Amplitude Modulation Links in C-Band for Short-Reach Optical Interconnects

Oskars Ozolins,Sandis Spolitis,Vjaceslavs Bobrovs,Aleksejs Udalcovs,Sergei Popov,Gunnar Jacobsen,Richard Schatz,Xiaodan Pang

doi:10.3390/app11094284

Abstract

We experimentally evaluate the high-speed on–off keying (OOK) and four-level pulse amplitude modulation (PAM4) transmitter’s performance in C-band for short-reach optical interconnects. We demonstrate up to 100 Gbaud OOK and PAM4 transmission over a 400 m standard single-mode fiber with a monolithically integrated externally modulated laser (EML) having 100 GHz 3 dB bandwidth with 2 dB ripple. We evaluate its capabilities to enable 800 GbE client-side links based on eight, and even four, optical lanes for optical interconnect applications. We study the equalizer’s complexity when increasing the baud rate of PAM4 signals. Furthermore, we extend our work with numerical simulations showing the required received optical power (ROP) for a certain bit error rate (BER) for the different combinations of the effective number of bits (ENOB) and extinction ratio (ER) at the transmitter. We also show a possibility to achieve around 1 km dispersion uncompensated transmission with a simple decision feedback equalizer (DFE) for a 100 Gbaud OOK, PAM4, and eight-level PAM (PAM8) link having the received power penalty of around 1 dB.

Highlights

Datacenters experience enormous traffic growth due to the vast amount of data to be stored, transmitted, and processed [1,2,3,4,5]
We point out that the histograms obtained with the 71-FFT and 15-FBT decision feedback equalizer (DFE) for the electrical b2b and the optical b2b signals at 90 Gbaud and 100 Gbaud are comparable in their performance
We focus on transmitter imperfections and chromatic dispersion (CD) tolerance

Summary

Introduction

Datacenters experience enormous traffic growth due to the vast amount of data to be stored, transmitted, and processed [1,2,3,4,5]. Solutions based on eight optical lanes [10,11,12,13,14,15], or even four optical lanes [16,17,18,19,20,21,22,23,24,25,26,27], for 800 GbE are more appealing thanks to the use of using high bandwidth components This allows reducing of costs, power consumption, and complexity of parallelism

Methods

Results

Conclusion