Flow-Controlled and Clock-Distributed Optical Switch and Control System

Switching the traffic in the optical domain has been considerably investigated as a future-proof solution to overcome the intrinsic bandwidth bottleneck of electrical switches in data center networks (DCNs). However, due to the lack of fast and scalable optical switch control mechanism, the lack of optical buffers for contention resolution, and the complicated implementation of fast clock and data recovery (CDR), the practical deployment of fast optical switches in data centers (DCs) remains a big challenge. In this work, we develop and experimentally demonstrate for the first time a flow-controlled and clock-distributed optical switch and control system, implementing 43.4 ns optical switch configuration time, less than 3.0E-10 packet loss rate resulting from the packet contention, and 3.1 ns fast CDR time. Experimental results confirm that zero buffer overflow caused packet loss and lower than $3~ \boldsymbol {\mu }\text{s}$ server-to-server latency are achieved for network deploying a smaller electrical buffer of 8192 bytes at a traffic load of 0.5. Real servers running the Transmission Control Protocol (TCP) traffic generating and monitoring tools are exploited in this switch and control system as well, validating its capability of running practical DCNs services and applications with full TCP bandwidth.

I. Introduction

With the large-scale deployment of high-traffic applications, such as high-definition streaming, cloud computing and 5G services, traffic growth in data centers (DCs) outpaces the bandwidth growth rate of application-specific integrated circuits (ASICs) electrical switch [1]. Because the Ball Grid Array (BGA) packaging technique is difficult to increase the pin-density, current ASICs electrical switches are expected to hit the bandwidth bottleneck in two generations from now [2]. As a future-proof solution supplying unlimited bandwidth, optical switching techniques have been considerably investigated to overcome this bandwidth bottleneck of electrical switches [3]. Being independent of the data-format and bit-rate, the optical switch can provide theoretical unlimited bandwidth benefiting from the optical transparency [4]. Moreover, switching the traffic in the optical domain removes the power-consuming and time-cost optical/electrical/ optical (O/E/O) conversions at the switch nodes. Optical switching could also eliminate the dedicated circuits and devices for various format modulation, hence, significantly decreasing the cost expenses as well as processing delay [5].