A Radiation Tolerant Laser Driver Array for Optical Transmission in the LHC Experiments

A 3-way Laser Driver ASIC has been implemented in deep-submicron CMOS technology, according to the CMS Tracker performance and rad-tolerance requirements. While being optimised for analogue operation, the full-custom IC is also compatible with LVDS digital signalling. It will be deployed for analogue and digital transmission in the 50.000 fibre link of the Tracker. A combination of linearization methods allows achieving good analogue performance (8-bit equivalent dynamic range, with 250 MHz bandwidth), while maintaining wide input common-mode range (±350 mV) and power dissipation of 10 mW/channel. The linearly amplified signals are superposed to a DC-current, programmable over a wide range (0-55 mA). The latter capability allows tracking of changes in laser threshold due to ageing or radiation damage. The driver gain and laser bias-current are programmable via a SEU-robust serial interface. The results of ASIC qualification are discussed in the paper.