Validation of the Optical Communication of the Serenity-S1 Board as Part of the CMS Phase 2 Upgrade

by Pirilsu Keskiner

Friday Sep 25, 2026, 10:15 AM → 11:00 AM Europe/Berlin

Seminarraum EG + zoom (IPE)

Final presentation of the Bachelor Thesis of Pirilsu Keskiner on the Validation of the Optical Communication of the Serenity-S1 Board as Part of the CMS Phase 2 Upgrade

Abstract
The Phase-2 upgrade of the Compact Muon Solenoid (CMS) experiment introduces the High Granularity Calorimeter (HGCAL), whose back-end electronics rely on Serenity-S1, a high-performance FPGA-based processing card in the Advanced Telecommunications Computing Architecture (ATCA) form factor. Of the 777 Serenity-S1 boards planned for CMS Phase-2 production, approximately 302 are allocated to HGCAL. Depending on a board’s functional role, Trigger Stage-1, Trigger Stage-2, or Data Acquisition (DAQ), it is populated with a different number and type of Samtec FireFly electro-optical modules, providing high-speed serial links at data rates of 10, 16, or 25 Gb/s. The existing production quality-control chain, comprising Factory Acceptance Testing (FAT) and User Acceptance Testing (UAT), verifies the fundamental electrical functionality of the boards and their high-speed links through copper-loopback connections and comparatively short bit-error-rate (BER) measurements, but does not validate the installed optical transmission paths or the I2C-based slow-control interfaces of the FireFly modules, which are the coverage that is essential before HGCAL integration.

This thesis presents the development and validation of an Optical Acceptance Test (OAT) framework for fully assembled Serenity-S1 boards. The framework validates the optical high-speed links under realistic operating conditions using both optical loopback and board-to-antiboard configurations, allowing individual channels as well as complete transmission paths to be examined systematically. Extended PRBS-based bit-error-rate measurements taken over longer observation periods assess link stability and identify marginal or faulty channels that shorter production tests may not reveal. In parallel, automated I2C-based communication tests verify the accessibility, configuration, and monitoring of every installed FireFly module, while relevant operating parameters, in particular supply voltage andtemperature, are monitored continuously. The entire procedure, from board configuration through test execution and system-health monitoring to the structured capture of results, is integrated into an automated software workflow.

For every tested board, the developed OAT framework produces reproducible test results and detailed diagnostic information, enabling the targeted identification of faults in optical links, FireFly modules, or their configuration that are not covered by the preceding production tests. The Optical Acceptance Test thereby adds a dedicated HGCAL specific validation stage between board acceptance and system integration, supporting the reliable qualification and large scale deployment of Serenity-S1 boards in the CMS Phase-2 HGCAL back end.

 

Zoom-Link: https://kit-lecture.zoom-x.de/j/65067123013?pwd=SXuK8pa9fEqpM72g7d9wc30Y02dUcg.1