Optical transceivers for event triggers in the ATLAS phase-I upgrade

TL;DR

This paper details the design, production quality control, and aging tests of optical transceivers used for event triggers in the ATLAS phase-I upgrade, focusing on high-speed, radiation-tolerant modules with high yield and stability.

Contribution

It presents the development and testing of radiation-hard optical transceivers with high production yield and long-term stability for use in high-energy physics experiments.

Findings

98% production yield for 4.7k modules

Stable operation with less than 5% power degradation over 6000 hours

Successful quality control based on eye-diagram parameters at 5.12 Gbps

Abstract

The ATLAS phase-I upgrade aims to enhance event trigger performance in the Liquid Argon (LAr) calorimeter and the forward muon spectrometer. The trigger signals are transmitted by optical transceivers at 5.12 Gbps per channel in a radiation field. We report the design, quality control in production and ageing test of the transceivers fabricated with the LOCld laser driver and multi-mode 850 nm vertical-cavity surface-emitting laser (VCSEL). The modules are packaged in miniature formats of dual-channel transmitter (MTx) and transceiver (MTRx) for the LAr. The transmitters are also packaged in small form-factor pluggable (SFP) for the muon spectrometer. In production, the LOCld chips and VCSELs in TOSA package were examined before assembly. All of the modules were tested and selected during production for quality control based on the eye-diagram parameters measured at 5.12 Gbps. The yield is 98 % for both the MTx and MTRx on a total 4.7k modules. The uniformity of transmitter channels of a MTx was assured by choosing the TOSA components with approximately equal light powers. The ageing effect is monitored in burn-in of a small batch of transmitter modules with bit-error test and eye-diagrams measured periodically. The observables are stable with the light power degradation within 5 % over a period of more than 6k hours.