Assembly of an optical bench of the Advanced Virgo gravitational wave detector in a clean room. It will observe the beam coming out of the end of an arm of the Advanced Virgo interferometer. It includes a telescope to reduce the size of the incoming beam from twenty centimeters to a few millimeters, different separators isolating several sub-beams analyzed by photodiodes and cameras. The data is scanned in the lower part. The generated signals will be used to monitor in real time the positions of the main mirrors of the Advanced Virgo interferometer and the measurement of the gravitational wave signal.