Analog optohybrids for the readout of the CMS silicon tracker

The Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider at CERN will include a Silicon Strip Tracker covering a sensitive area of 206 m2 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 100 m. 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 −10°C in a magnetic field of 4 T 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.