Characteristics of the MTx optical transmitter in Total Ionizing Dose

TL;DR

This study investigates the effects of Total Ionizing Dose radiation on the MTx optical transmitter used in high-energy physics experiments, revealing its radiation tolerance and performance stability under irradiation.

Contribution

It provides the first detailed analysis of TID effects on the MTx optical transmitter's components, including VCSEL diodes and laser drivers, under various radiation doses and rates.

Findings

Degradation of laser currents at 10-100 Gy(SiO2) with partial recovery

Optical eye diagrams remain suitable for 5 Gbps data transmission after irradiation

The MTx maintains stable output with about 90% of original performance after TID exposure

Abstract

The dual-channel multi-mode 850 nm optical Miniature Transmitter (MTx) is developed for data transmission of the ATLAS LAr calorimeter readout at LHC. The MTx's are exposed to the radiation field of proton-proton collisions, therefore, the tolerance in Total Ionizing Dose (TID) is required. The TID effects in the MTx are investigated with X-rays and Co-60 gamma-rays for the active components of VCSEL diodes and the customized Link-on-Chip laser driver (LOCld) developed in 0.25 um Silicon-on-Sapphire CMOS technology. The irradiation tests were conducted at various dose rates. The responses to TID are observed with degradation of laser currents at initial dose of 10 to 100 Gy(SiO2), and partial recovery with additional TID to a stable output about 90 % of the original. The optical eye diagrams of irradiated samples show slightly increased jittering, and are suitable for the ATLAS requirement of 5 Gbps applications.