A Method for the Static Characterisation of the CMS Tracker Analogue Optical Links

Analogue optical links are being developed for the CMS-Tracker. The large envisaged number of physical channels ( over 50.000) imposes semi-automated test procedures and efficient evaluation criteria to compare different link solutions, to optimise their performance, and to confirm their compliance with specifications when commissioning the system. In addition, self-triggered calibration schemes need to be developed to maintain the readout chain accuracy during the detector lifetime ( 10 years). In this paper we present a method for the static characterisation of the CMS analogue optical links, relying on an automated setup for gain, rms-noise and linearity measurements, and on a software program for off line processing of the test data. We propose a set of evaluation criteria and describe a compact representation of the results in the operational parameter space ( working point, operating range). This representation allows to quantify and compare the performance of links based on different components, as well as to develop and simulate practical testing and calibration procedures.