The Distributed Oscilloscope: A Large-Scale Fully Synchronised Data Acquisition System Over White Rabbit

A common need in large scientific experiments is the ability to monitor by means of simultaneous data acquisition across the whole installation. Data is acquired as a result of triggers which may either come from external sources, or from internal triggering of one of the acquisition nodes. However, a problem arises from the fact that once the trigger is generated, it will not arrive to the receiving nodes simultaneously, due to varying distances and environmental conditions. The Distributed Oscilloscope (DO) concept attempts to address this problem by leveraging the sub-nanosecond synchronization and deterministic data delivery provided by White Rabbit (WR) and augmenting it with automatic discovery of acquisition nodes and complex trigger event scheduling, in order to provide the illusion of a virtual oscilloscope. This paper presents the current state of the DO, including work done on the FPGA and software level to enhance existing acquisition hardware, as well as a new protocol based on existing industrial standards. It also includes test results obtained from a demonstrator based on two digitizers separated by a 10 km optical fiber, used as a showcase of the DO concept.