PAM Performance Analysis in Multicast-Enabled Wavelength-Routing Data Centers
Journal article, 2017

Multilevel pulse amplitude modulation (M-PAM) is gaining momentum for high-capacity and power-efficient cloud computing. Compared to the classic on-off keying (OOK) modulation, high-order PAM yields better spectral efficiency but is also more susceptible to physical layer degradation effects. We develop a cross-layer analysis framework to examine the PAM transmission performance in data center network environments supporting both optical multicasting and wavelength routing. Our analysis is conducted on a switch architecture based on an arrayed-waveguide grating (AWG) core and distributed broadcast domains, exhibiting different physical paths, and random, uncontrolled crosstalk noise. Reed-Solomon coding with rate adaptation is incorporated into PAM transceivers to compensate for impairments. Our Monte Carlo simulations point to the significant impact of AWG crosstalk on higher order PAM in wavelength-reuse architectures and the importance of code rate adaptation for signals traversing multiple routing stages. According to our study, 8-PAM offers the highest effective bit rates for signals terminating in one broadcast domain and performs poorly when considering interdomain connectivity. On the other hand, the impairment-induced degradation of interdomain capacity for 4-PAM can be limited to 20.7%, making it better suited for connections spanning two broadcast domains and a crosstalk-rich stage. Our results call for software-defined PAM transceiver designs in support of both modulation order and code rate adaptation.

pulse amplitude modulation (PAM)

forward error correction (FEC)

data center

bit error rate (BER)

optical multicast

Arrayed waveguide grating (AWG)

physical layer



Houman Rastegarfar

Chalmers, Signals and Systems, Communication, Antennas and Optical Networks

Li Yan

Chalmers, Signals and Systems, Communication, Antennas and Optical Networks

Krzysztof Szczerba

Finisar Corporation

Erik Agrell

Chalmers, Signals and Systems, Communication, Antennas and Optical Networks

Journal of Lightwave Technology

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

Vol. 35 13 2569-2579 7892938

Towards flexible and energi-efficient datacentre networks

Swedish Research Council (VR) (2014-6230), 2015-01-01 -- 2018-12-31.

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