EN
The infrared emission of Tm^{3+}/Ho^{3+}-doped antimony-silicate optical fiber has been presented. Luminescence at 2.1 μm corresponding to ⁵I₇ → ⁵I₈ transition in holmium was obtained by energy transfer between Tm^{3+} and Ho^{3+} ions. According to the Förster-Dexter theory, the efficiency of energy transfer of the ³F_4 (Tm^{3+}) → ⁵I₇ (Ho^{3+}) transition was calculated. The optimization of the activator content and the donor (Tm^{3+})/acceptor (Ho^{3+}) ions concentration ratio were conducted with the purpose of maximizing the efficiency of energy transfer. It made possible to select best-suited glass which was used to manufacture double-clad optical fiber. Strong and narrow bands of amplified spontaneous emission which formed as a result of energy transfer between thulium and holmium ions were observed in the fiber under exciting with radiation at 795 nm wavelength.