Development of the Optical Multiplexer Board Prototype for Data Acquisition in the TileCal System

This paper describes the development of the optical multiplexer board (OMB), also known as PreROD board, for the TileCal readout system in the ATLAS experiment. The aim of this board is to overcome the problems that may arise in the integrity of data due to radiation effects. The solution adopted has been to add redundancy to data transmission and so two optical fibers with the same data come out from the detector front end boards. The OMB has to decide in real time which fiber, eventually, carries data with no errors switching it to the output link connected to the read out driver (ROD) motherboard where data processing takes place. Besides, the board may be also used as a data injector for testing purposes of the ROD motherboard. The paper describes the design and tests of the first prototype, implemented as a 6U VME64x slave module, including both hardware aspects, focusing on signal integrity problems, and firmware aspects, dealing with the cyclic redundancy code algorithms used to check data consistency used to make the decision