What Devices do Data Centers Need?

Lam, Cedric F.; Liu, Hong; Urata, R.

doi:10.1364/ofc.2014.m2k.5

Cited by 21 publications

(9 citation statements)

References 6 publications

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“…The authors reported a considerable decrease of the inter-modal crosstalk due to an increase of the refractive index separation. Such optical fibers could be very promising for data centerguided interconnects [322]. The ring-core graded index fiber, reported in [318], and over which an 18 km OAM-WDM transmission with a low crosstalk was demonstrated, could be also used for interconnect applications.…”

Section: F Oam Maintaining Fibersmentioning

confidence: 99%

Communicating Using Spatial Mode Multiplexing: Potentials, Challenges, and Perspectives

Trichili

Park

Zghal

et al. 2019

IEEE Commun. Surv. Tutorials

189

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Time, polarization, and wavelength multiplexing schemes have been used to satisfy the growing need of transmission capacity. Using space as a new dimension for communication systems has been recently suggested as a versatile technique to address future bandwidth issues. We review the potentials of harnessing the space as an additional degree of freedom for communication applications including free space optics, optical fiber installation, underwater wireless optical links, on-chip interconnects, data center indoor connections, radio frequency and acoustic communications. We focus on the orbital angular momentum (OAM) modes and equally identify the challenges related to each of the applications of spatial modes and the particular OAM modes in communication. We further discuss the perspectives of this emerging technology. Finally, we provide the open research directions and we discuss the practical deployment of OAM communication links for different applications. ). 4 in the future. We also summarize the open problems and the future research directions. A discussion of the practicability and cost of multi-OAM communication is also included. II. OAM POTENTIALS A. Free Space Optical CommunicationFSO is a license free wireless communication configuration that has recently received much interest for a variety of applications. FSO is an attractive solution for last mile connectivity problems, particularly for communication networks, when the installation of fiber optics is costly or not possible [66]. FSO can be also used to establish inter-building secure communication, and can be deployed as a backup to optical fibers. Wireless optical communication can guarantee a line-of-sight (LoS) high bit rate wireless transmission over long distances, up to several kilometers. Furthermore, FSO communication is considered as a promising technique to scale down bandwidth challenges in future 5G networks [67].Multiple wavelength FSO provides better transmission, as demonstrated in [68], [69]. Data can be mapped on advanced modulation formats to achieve high bit rates and high spectral efficiency levels [70]- [72]. Another option is multiple-input and multiple-output (MIMO) FSO communication in which multiple lasers are positioned to transmit Gaussian beams to multiple receiving apertures [73]. Over the last few years, it has been proven that it is possible to transmit information over spatially structured light beams [21], [74], [75] including OAM beams and plane waves. Our focus is on the OAM modes of light.The first PoC communication experiment incorporating OAMs in free space was carried out in 2004 by Gibson and co-workers [21]. Over a 15-meter long link, 8 -spaced values were chosen along the Gaussian beam as an alphabet for the communication. OAM beams were generated and detected using two light modulators. Since then, much progress has been made and free space transmission capacity of over 1 Tbit/s is, today, possible [76]- [78]. By performing three dimensional multiplexing, Huang and co-workers were able to attain a 100 Tbi...

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Section: F Oam Maintaining Fibersmentioning

confidence: 99%

Communicating Using Spatial Mode Multiplexing: Potentials, Challenges, and Perspectives

Trichili

Park

Zghal

et al. 2019

IEEE Commun. Surv. Tutorials

189

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“…We consider two major types of impairments: ASE noise due to active devices and crosstalk due to passive devices in an optical buffer module. As data center links are typically between a few meters to hundreds of meters long [105,106], we ignore dispersion and nonlinear propagation effects in short-reach single-mode fibers. Besides, in a high density data center network, requiring tight channel spacing and high bit rate signals, signal impairment due to filter concatenation effects and pass-band misalignments could lead to a crucial impact that is beyond the scope of this thesis and requires further investigation.…”

Section: Physical Layer Impairmentsmentioning

confidence: 99%

“…With the exponential increase in data center traffic and the expected drop in price points, data centers will eventually migrate to optical coherent technologies [20,106]. One interesting research problem will be to examine the cross-layer performance of OPS data center subsystems for advanced optical modulation formats.…”

Section: Advanced Optical Technologiesmentioning

confidence: 99%

Optical Switching in Next Generation Data Centers

Testa¹,

Pavesi²

2018

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This thesis presents advanced optical connectivity solutions for next-generation data centers, spanning millions of processing cores. The wavelength routing of optical packets based on arrayed waveguide gratings (AWGs), tunable wavelength converters (TWCs), and fiber delay lines (FDLs) is a disruptive technology for capacity, footprint, and flexibility requirements of massive cloud data centers. We develop a wavelength-division multiplexed (WDM) design based on Birkhoff-von Neumann architecture as a bitrate transparent, scalable solution to switching bottlenecks in data center networks. As no mature all-optical buffering technology is currently available, central to our design is the buffering strategy that we adopt to store contending packets. Due to the limited number of FDLs, packet drops are common in optical packet switching (OPS) data centers and limit the network throughput. In a practical scenario, physical layer impairments, predominantly amplified spontaneous emission (ASE) noise and crosstalk, degrade Q-factor and lead to additional packet drops. To examine the performance of optical buffer units more accurately, we develop a unified analysis framework, integrating the network layer and the physical layer effects. Using this framework, we refine our architectures and provide guidelines for minimizing the physical layer impact. Besides, optical switch designs should not neglect the diversity of data center traffic patterns when developing connectivity solutions. Empirical studies of data center network traffic reveal that server traffic exhibits strong spatial and temporal correlations. We examine the effectiveness of an AWG-based load balancer with round-robin tuning TWCs in resolving congestion penalties in the data center network. Our cross-layer analysis suggests that the physical layer impairments due to the load balancer hardware could counteract its potential gains and lead to significant throughput degradation. To resolve this challenge, we develop a novel modular router architecture based on WDM shared recirculation buffers that integrates the functions of load balancing and routing and maximizes the optical buffering gains. The router employs a load-balancing scheduler to maximize throughput and minimize delay. Our mathematical analysis and Monte Carlo simulations show that the consolidation of optical buffer slots into WDM FDLs accompanied with internal load balancing leads to a virtually lossless router, resilient to data center traffic anomalies.ii

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“…Requirements for optical interconnects are that they be high-speed, have a longer transmission distance, be highly reliable and so on. However, the most pressing requirement that they be low cost [2], [3]. To satisfy these requirements, in an earlier study we developed a cost-effective flexible printed circuitbased optical engine (FPC-OE) [4], [5] with a polymer waveguide [6].…”

Section: Introductionmentioning

confidence: 99%

Structure of 25-Gb/s Optical Engine for QSFP Enabling High-Precision Passive Alignment of Optical Assembly

Yagisawa

Mori

Gappa

et al. 2016

2016 IEEE 66th Electronic Components and Technology Conference (ECTC)

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We propose a novel structure for optical assembly that enables high-precision passive alignment assembly process for our flexible printed circuit-based optical engine. The optical engines are fabricated with less than 7 ȝm of misalignment between optical devices and polymer waveguides. This high-precision alignment suppresses the optical coupling losses to an average of 2.9 dB for the transmitter side and, 1.6 dB for the receiver side. The optical engines are installed to a high-volume product of 100 Gb/s quad small form-factor pluggable (QSFP) optical transceivers. The QSFP demonstrated clear eye opening and error-free operation at 100Gb/s with high yield rate thanks to the low-coupling loss resulting from the high-precision alignment of optical devices.

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What Devices do Data Centers Need?

Abstract: Abstract:We discuss the trend in fiber optic technology developments to fulfill the scaling requirements of datacenter networks.

Cited by 21 publications

References 6 publications

Communicating Using Spatial Mode Multiplexing: Potentials, Challenges, and Perspectives

Communicating Using Spatial Mode Multiplexing: Potentials, Challenges, and Perspectives

Optical Switching in Next Generation Data Centers

Structure of 25-Gb/s Optical Engine for QSFP Enabling High-Precision Passive Alignment of Optical Assembly

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