Optoelectronic~Analogue~Signal~Transfer~for~LHC~Detectors

% RD23 \\ \\ \\ \\The main goal of the RD23 project is to develop optical fiber links for volume application in the analog signal transfer of tracking detectors at LHC. Key requirements were radiation hardness, low power dissipation and affordable cost. The technique proposed initially was based on external modulation, and the project was targeted at the development of electro-optic intensity modulators as transmitters. In 1996, this approach was abandoned in favor of a system based on directly modulated semiconductor laser transmitters. This configuration was subsequently adopted as baseline choice by the CMS experiment for its tracker readout system. \\ \\In view of qualifying the radiation hardness of all optical link components to be installed at LHC front-ends, extensive validation tests took place in 1997 and 1998. Irradiations of lasers, pin-diodes, optical fibers and connectors were carried out with neutrons ($\sim$6MeV) and $^{60}$Co gamma rays. In addition, lasers and pin-diodes in die as well as packaged form were also tested with protons (24GeV) and pions (300MeV). Results indicate that devices from several different manufacturers can survive LHC-tracker environments for the lifetime of the experiments. Accelerated aging test of irradiated lasers connectors and pin-diodes were carried out, in order to evaluate the reliability of radiation-damaged components.\\ \\Complete analog and digital data link prototypes were successfully realized and tested using the same optoelectronic components as tested for radiation hardness. A 4-channel low-mass, radiation-hard and non-magnetic package was developed in collaboration with industry, to house up to 4 laser transmitters or photodiode receivers.