-9891 cm -1 , 9775 cm -1 , 9653 cm The number of luminescence lines being obtained on the 2 F5/2 → 2 F7/2 transition of Yb 3+ is five, that exceeds the calculated value (four), therefore, there are at least two types of optical centers of the ytterbium ion in the YScO3 crystal fiber. As shown in the works , two types of optical centers exist in both Y2O3 and Sc2O3 crystals doped with Yb 3+ ions: a) low-symmetric in the C2 site, and b) high-symmetric one in the C3i site. The Stark component energies for these two types of Yb 3+ optical centers in both Y2O3 and Sc2O3 crystals are obtained at T=10K in and shown in Figure . The largest splitting of the 2 F7/2 level is observed for the center with C2 local symmetry in the Sc2O3 crystal. Calculations on crystal field theory have been performed in to determine the Stark component energies and the the 2 F7/2 and 2 F5/2 for Yb3+ ions in the Y2O3, yielding results that are in good agreement with previous studies . symmetries of C2 (Y 3+ ), C3i (Y 3+ ), and C2 (Sc 3+ ). In the case of a single low-symmetry center II (Yb 3+ ), the luminescence spectra of the ytterbium ion can be attributed to optical centers with local symmetries of C2 (Sc 3+ ) and C2 (Y 3+ ), which lines are overlapped (see Figure ).