The precise shape measurement of fast rotating objects is a challenging task in metrology. Deformation measurements of lightweight composite materials are important to guarantee its robustness e.g. against impacts since they cannot be simulated reliably. In a high-speed rotor test rig, their elastic and plastic deformations due to centrifugal forces can be evaluated. Non-contact inspection techniques with micron resolution under vacuum conditions are necessary. We present for the first time deformation measurements of a high-speed cylindrical rotor by a non-incremental interferometric array sensor system. Rugged compact sensors were realised by employing optical fibers and diffractive optics. Unique is the determination of the radial expansion also in the presence of an unsteady tumbling motion of the rotor which is also monitored.