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.