Designing a passive star optical network for the India-based Neutrino Observatory

The India-based Neutrino Observatory (INO) uses an iron calorimeter (ICAL) as the neutrino detector. The ICAL consist of 28, 800 resistive plate chambers (RPCs) that generate event data at ~ 650 kbps, for an aggregate of 18 Gbps at the backend. Implementation of a triggerless detection scheme will increase this by a factor of 20. We describe a passive star optical network (PSON) and provide a data networking scheme for the ICAL. We discuss the need of a custom designed communication protocol (ICAL-PRO) for PSON and present its 4 layer architecture and data flow. We use a microcontroller based embedded model to demonstrate a 1 × 16 PSON and discuss its packet error rate (PER) analysis. We achieve a PER of <; 10^-9 at the operational signal to noise ratio (SNR) value. We implement time synchronization in the 1 × 16 PSON and achieve an accuracy between 200 - 300 ns. We substantiate the operational principle of ICAL-PRO by successfully demonstrating a 1 × 16 PSON.