Beyond 1 Tb/s Intra-Data Center Interconnect Technology: IM-DD OR Coherent?

We discuss technology options and challenges for scaling intra-datacenter interconnects beyond 1 Tb/s bandwidths, with focus on two possible approaches: pulse amplitude modulation (PAM)-based intensity modulation-direct detection (IM-DD) and baud-rate sampled coherent technology. In our studies, we...

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Bibliographic Details
Published in:Journal of lightwave technology Vol. 38; no. 2; pp. 475 - 484
Main Authors: Zhou, Xiang, Urata, Ryohei, Liu, Hong
Format: Journal Article
Language:English
Published: New York IEEE 15.01.2020
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Bandwidth
Coherence
Coherent detection
coherent modulation
Comparative studies
Data centers
datacenter
Digital signal processing
direct detection
DSP
fiber
FlexPAM
IM-DD
interconnect
modulation format
optical
Optical fibers
Optical interconnections
Optical modulation
Optical polarization
PAM
Power consumption
Pulse amplitude modulation
QAM
Quadrature amplitude modulation
ISSN:0733-8724, 1558-2213
Online Access:Get full text
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Summary:We discuss technology options and challenges for scaling intra-datacenter interconnects beyond 1 Tb/s bandwidths, with focus on two possible approaches: pulse amplitude modulation (PAM)-based intensity modulation-direct detection (IM-DD) and baud-rate sampled coherent technology. In our studies, we compare the performance of various orders of PAM modulation (PAM4 to 8). In addition to these fixed PAM signaling options, a flexible PAM (FlexPAM) technique leveraging granularity in spectral efficiency (SE) is proposed to maximize link margin. For baud-rate sampled coherent technology, we propose a simplified digital signal processing (DSP) architecture to bring down power consumption of the coherent approach closer to that of IM-DD PAM. We also propose two new phase noise tolerant 2D coherent modulation formats to relax the laser linewidth requirement. In closing, a comparative study of fixed IM-DD PAM versus coherent polarization multiplexed-quadrature amplitude modulation (PM-QAM) is presented for a 1.6 Tb/s solution (200 Gb/s per dimension), with consideration of link loss/reach budget, power consumption, implementation complexity, as well as fan-out granularity.
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ISSN:0733-8724
1558-2213
DOI:10.1109/JLT.2019.2956779