Analog Optohybrids for the Readout of the CMS Silicon Tracker

The Compact Muon Solenoid experiment (CMS) at the Large Hadron Collider (LHC) at CERN will include a Silicon Strip Tracker covering a sensitive area of 206m2 with about 9.3 million channels. The particle signals are read out by APV25 front-end chips and transferred to the processing units using approximately 37,000 optical links over a distance of about 100m. In order to convert the electrical signals to intensity-modulated light, roughly 15,000 optohybrids with 2 or 3 channels each will be distributed in the Tracker volume. These devices are designed to operate at -10C in a magnetic field of 4T and the harsh radiation environment of CMS with good linearity and low noise. Single-mode optical fibers will guide the light to 12-way pin diode arrays converting it back to electrical signals for digitization and processing. Custom-specific optoelectronics and ASICs are involved on both ends of the optical links.