Enabling high performance rack-scale optical switching through global synchronisation

There is a growing need for high radix switches in data centres and high performance computing. Current computing systems are interconnected using large numbers of relatively low radix (32--48 port) switches that restrict scalability and performance, while increasing cost and management complexity. In parallel, there is a growing interest in dense rack scale computing in which a single rack can contain several thousand network nodes. To meet these demands, we recently demonstrated a flexible optical switch architecture using fast tuneable lasers and coherent receivers which scales to over 1000 ports. However, using traditional clock data recovery circuits in this or any optical packet switch results in large latency and throughput penalties due to resynchronisation on each new connection. In this talk, we will address the challenges of building a fully synchronous optical switch network, of rack-scale or greater, in which a reference clock is distributed to every node to reduce resynchronisation overhead. We will firstly present results from preliminary FPGA-based experiments demonstrating the viability of synchronising a rack scale network. We will then discuss the limitations on port count, range and bit rate which would limit the ability to build larger synchronous systems in this way.