Choice of the WLS fibres for the Tilecal calorimeter

We report on the criteria and measurements performed for the choice of the type of fibre that would equip the Tilecal Calorimeter. There were three types of candidate WLS fibres each from a different producer: BCF91A from Bicron, S250-100 from Pol.Hi.Tech and Y11(200)MSJ from Kuraray. The three producers have a history of cooperation with the Tilecal/ATLAS group and some of those fibres were used to instrument several prototype modules of the Tilecal. After many tests, the fibres that were chosen to equip the Tilecal were the Y11(200)MSJ from Kuraray.