Arteche, A. Bosco, A. Chritin, N. Draskovic, D. Gibson, S.M. Lefèvre, T. Levens, T.E. JACoW Geneva, Switzerland 978-3-95450-177-9 10.18429/JACoW-IBIC2016-WEPG09 English 635-638 WEPG09 pick-up polarization laser proton optics Contribution to a conference proceedings 2017 2017-02 http://dx.doi.org/10.18429/JACoW-IBIC2016-WEPG09 http://jacow.org/ibic2016/papers/wepg09.pdf A novel electro-optic beam position monitor capable of rapidly (<50ps) monitoring transverse intra-bunch perturbations is under development for the HL-LHC project. The EO-BPM relies on the fast optical response of two pairs of electro-optic crystals, whose birefringence is modified by the passing electric field of a 1ns proton bunch. Analytic models of the electric field are compared with electromagnetic simulations. A preliminary opto-mechanical design of the EO-BPM was manufactured and installed at the CERN SPS in 2016. The prototype is equipped with two pairs of 5mm cubic LiNbO3 crystals, mounted in the horizontal and vertical planes. A polarized CW 780nm laser in the counting room transmits light via 160m of PM fibre to the SPS, where delivery optics directs light through a pair of crystals in the accelerator vacuum. The input polarization state to the crystal can be remotely controlled. The modulated light after the crystal is analyzed, fibre-coupled and recorded by a fast photodetector in the counting room. Following the recent installation, we present the detailed setup and report the latest status on commissioning the device in-situ at the CERN SPS.