A Timing, Trigger, and Control System With Picosecond Precision Based on 10 Gbit/s Passive Optical Networks for High-Energy Physics

Abstract

The Large Hadron Collider (LHC) experiments will have their timing, trigger, and control (TTC) system upgraded as a consequence of the need for higher bandwidth and components which are obsolete. In this article, we present a TTC based on passive optical networks (PONs). TTC-PON is a point-to-multipoint bidirectional TTC system based on the 10 Gbit/s International Telecommunications Union (ITU) XG-PON technology and modern field-programmable gate array (FPGA) devices. Each master can handle up to 64 slaves through a fully passive network, delivering a fixed-phase recovered clock to all the destinations with less than 5-ps jitter. TTC-PON pushes the limits of the PON technology by exploiting cutting-edge custom protocols on top of the commercially available XG-PON optical modules. It can potentially reuse the current optical fiber infrastructure already installed in the experiments and allows for high flexibility in terms of partitioning, which can ease future upgrades of the TTC network. The system features a picosecond-level on-the-fly phase monitoring for each slave's recovered clock by exploiting the bidirectionality of the network. In addition, a full set of link-quality monitoring tools was developed, allowing real-time performance monitoring. An overview of the tailored protocols will be given together with the details on the system implementation, operation, and performance. A discussion on the characterization campaign of more than 1000 optical modules delivered to the first implementation of the TTC-PON system will be drawn.