The TileCal Optical Multiplexer Board 9U

TileCal is the hadronic calorimeter of the ATLAS experiment at LHC/CERN. The system contains roughly 10,000 channels of read‐out electronics, whose signals are gathered and digitized in the front‐end electronics and then transmitted to the counting room through two redundant optical links. Then, the data is received in the back‐end system by the Optical Multiplexer Board (OMB) 9U which performs a CRC check to the redundant data to avoid Single Event Upsets errors. A real‐time decision is taken on the event‐to-event basis to transmit single data to the Read‐Out Drivers (RODs) for processing. Due to the low dose level expected during the first years of operations in ATLAS it was decided not to use a redundant system and currently the front‐end electronics is directly connected to the RODs. However, the increasing luminosity of the LHC will force to use the redundant read‐out and the OMB system will be installed. Moreover, the OMB can be used as a ROD injector to emulate the front‐end electronics for ROD software tests during detector maintenance periods taking advantage of its location in the data acquisition chain. First we will give a detailed description of the main components of the board and the different operation modes. Then, the production and qualification tests will be explained including a detailed description of the test‐bench, software and validation protocols.