Free Space Intra-Datacenter Interconnects Based on 2D Optical Beam Steering Enabled by Photonic Integrated Circuits

Abstract

Data centers are continuously growing in scale and can contain more than one million servers spreading across thousands of racks; requiring a large-scale switching network to provide broadband and reconfigurable interconnections of low latency. Traditional data center network architectures, through the use of electrical packet switches in a multi-tier topology, has fundamental weaknesses such as oversubscription and cabling complexity. Wireless intra-data center interconnection solutions have been proposed to deal with the cabling problem and can simultaneously address the over-provisioning problem by offering efficient topology re-configurability. In this work we introduce a novel free space optical interconnect solution for intra-data center networks that utilizes 2D optical beam steering for the transmitter, and high bandwidth wide-area photodiode arrays for the receiver. This new breed of free space optical interconnects can be developed on a photonic integrated circuit; offering ns switching at sub-µW consumption. The proposed interconnects together with a networking architecture that is suitable for utilizing those devices could support next generation intra-data center networks, fulfilling the requirements of seamless operation, high connectivity, and agility in terms of the reconfiguration time.Photonics 2018, 5, 21 2 of 10 traffic increases. New architectures (e.g., based on modular designs) have been recently proposed addressing these issues [4]. However, the proposed solutions impose other challenges that demand low-cost/low-power dynamic re-configurability and seamless scalability [5].Optical fibers and fiber-pigtailed transceivers are the key elements in constructing traditional DCNs. Millions of meters of fiber are required, forming an extremely complex cabling system that is difficult to manage [6], with the choice of cabling architecture greatly influencing the throughput, scalability, and energy efficiency management of a DC [6,7]. Although the cabling problem is still underestimated, when the scaling and cost of large infrastructures is under consideration, recent studies have started paying attention to its side effects. For instance, it was shown that the mass of long cables between the switches causes great difficulties in system maintenance [5]. When the network connection changes or line failure occurs, the system upgrading becomes extremely complicated. IBM also reported that the dense cabling will affect the heat dissipation due to the fact that airflow is obstructed [8], while HP reported that mapping a logical topology with servers, switches, and links onto a physical space with racks and cable trays such that the cable costs are minimized is a non-deterministic polynomial-time hard (NP-hard) problem [9].At the same time, the traditional way of designing DCNs, through the use of electrical packet switches in a multitier topology, has a fundamental weakness, namely that it has to be decided in advance whether to provide overprovisioned or oversubscribed interconnects between top of rack ...

LightFDG: An Integrated Approach to Flow Detection and Grooming in Optical Wireless DCNs

“…1 where optical transceivers of ESs are connected to CS transceivers located at the top. WDM-FSO links can be implemented by photonic integrated circuits (PIC) [35] or photo-diode array [36] based transmitters to steer the lightbeam to the photodiode receivers. Since transceivers are not required to change their direction after the setup, an alternative approach is setting gimbals atop the racks and directing transmitter and receiver towards each other 1 .…”

“…In this section, we measure the FD overhead on the CU and the network. Even though the previous network setup python library [35], configure top Linux tool to collect the device statistics for every second, and store them on a particular file. For all evaluations, the CU needs to setup the network and prepare the OvS switches with necessary configurations as well as sFlow rules defined at start-up phase.…”

Beyond 5G - wireless data center connectivity

“…13 Beyond the THz range, at much higher frequencies, optical wireless communications, where optical signal are transmitted through open space with collimated beams, rather than guided via optical fiber, can offer significant capacities and has been suggested as an alternative for data center networking. 13,24 While the typical telecommunications and fiber optics wavelengths -at 850 nm, 1310 nm and 1550 nm -are obvious candidate for such free space optics (fso) implementations, the available spectrum is much larger and extends across the entire infrared region and beyond to visible light. As such the available spectrum is multiple times larger than in rf mm-wave and THz, making up for the potentially lower spectral efficiency, while benefiting from potentially improved transmission characteristics, immunity to rf interference, higher transmitter density and the chance for increased spectrum reuse.…”

“…For instance, two-dimensional steering can be achieved using mico-mechanical mirror or with fully integrated optical chips based on tunable lasers and waveguide gratings. 13,24 The potential to concurrently emit tens or even hundreds of high-bandwidth wireless signals from a single array while maintaining spatial separation and avoiding interference by beamforming is key whenever a high density of large capacity connections is required -i.e., in crowded areas with many mobile users and in wireless data centers alike. Similarly, the flexibility afforded by being able steer the beam is of great value in both mobile networks and wireless data centers, allowing dynamic following of users in the former and providing dynamic reconfigurability to meet changing load and requirements in the latter.…”

Data Center Connectivity by 6G Wireless Systems

“…Moreover, wired typologies render the network static and inflexible, not only impacting energy efficiency, but also scalability of the overall data center. Typical data center network architectures are based on scale-up hierarchical designs such as fat-tree and butterfly, which have drawbacks like poor reconfigurability and scalability [2].…”