Design and Preliminary Implementation of an N $\times$ N Diffractive All-Optical Fiber Optic Switch

Lynn, Brittany; Blanche, Pierre Alexandre; Miles, Alexander; Wissinger, John; Carothers, Daniel; LaComb, Lloyd; Norwood, Robert A.; Peyghambarian, N.

doi:10.1109/jlt.2013.2280431

Cited by 19 publications

(7 citation statements)

References 12 publications

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“…Second, the size of MEMS switches limit the scale of the data center. Available commercial MEMS switches are limited in size to 320 ports, although experimental demonstrations of a few thousands of ports have been reported [69,73,76,78].…”

Section: Optical Circuit Switching Designsmentioning

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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Section: Optical Circuit Switching Designsmentioning

confidence: 99%

Optical Switching in Next Generation Data Centers

Testa¹,

Pavesi²

2018

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“…To demonstrate the potential of an holographic-based optical switch, we used a Texas Instruments DLP (Digital Light Processing) in our initial prototype [15,16]. The DLP is a MEMS where the mirrors can be tilted in two different directions.…”

Section: Diffraction-based Optical Switchingmentioning

confidence: 99%

Diffraction-Based Optical Switching with MEMS

et al. 2017

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Abstract:We are presenting an overview of MEMS-based (Micro-Electro-Mechanical System) optical switch technology starting from the reflective two-dimensional (2D) and three-dimensional (3D) MEMS implementations. To further increase the speed of the MEMS from these devices, the mirror size needs to be reduced. Small mirror size prevents efficient reflection but favors a diffraction-based approach. Two implementations have been demonstrated, one using the Texas Instruments DLP (Digital Light Processing), and the other an LCoS-based (Liquid Crystal on Silicon) SLM (Spatial Light Modulator). These switches demonstrated the benefit of diffraction, by independently achieving high speed, efficiency, and high number of ports. We also demonstrated for the first time that PSK (Phase Shift Keying) modulation format can be used with diffraction-based devices. To be truly effective in diffraction mode, the MEMS pixels should modulate the phase of the incident light. We are presenting our past and current efforts to manufacture a new type of MEMS where the pixels are moving in the vertical direction. The original structure is a 32 × 32 phase modulator array with high contrast grating pixels, and we are introducing a new sub-wavelength linear array capable of a 310 kHz modulation rate.

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“…DMDs can steer light in tens of thousands of directions, depending on their configuration, and they can switch between different directions in 12 µs. Prior work has used DMDs for low port-count optical switches [28,32]; we explore their use in building a DC-wide interconnect.…”

Section: Msmentioning

confidence: 99%

ProjecToR

Ghobadi

Mahajan

Phanishayee

et al. 2016

Proceedings of the 2016 ACM SIGCOMM Conference

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220

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We explore a novel, free-space optics based approach for building data center interconnects. It uses a digital micromirror device (DMD) and mirror assembly combination as a transmitter and a photodetector on top of the rack as a receiver (Figure 1). Our approach enables all pairs of racks to establish direct links, and we can reconfigure such links (i.e., connect different rack pairs) within 12 µs. To carry traffic from a source to a destination rack, transmitters and receivers in our interconnect can be dynamically linked in millions of ways. We develop topology construction and routing methods to exploit this flexibility, including a flow scheduling algorithm that is a constant factor approximation to the offline optimal solution. Experiments with a small prototype point to the feasibility of our approach. Simulations using realistic data center workloads show that, compared to the conventional folded-Clos interconnect, our approach can improve mean flow completion time by 30-95% and reduce cost by 25-40%.

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Design and Preliminary Implementation of an N $\times$ N Diffractive All-Optical Fiber Optic Switch

Cited by 19 publications

References 12 publications

Optical Switching in Next Generation Data Centers

Optical Switching in Next Generation Data Centers

Diffraction-Based Optical Switching with MEMS

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