M. Gawlikowski, P. Kurtyka, J. Zalewski, M. Zarwańska-Doffek, and A. Kapis, “Methodology for measuring the gap size using a fiber-optic displacement sensor exemplified by a centrifugal blood pump”, Photonics Lett. Pol., vol. 12, no. 2, pp. 46–48, Jul. 2020.