We developed and characterized luminescent temperature sensors with a simple construction based on YAG : Ln^{3 +} (Ln = Nd, Yb, Ce) nanocrystals and silica multimode optical fibers. Lanthanide-doped nanocrystals 40 to 60 nm in size were synthesized in the form of powders using the modified Pechini method. The obtained materials exhibited high sensitivity of luminescence intensity to temperature variations at wavelengths of 550 nm (YAG : Ce^{3 +} ), 1030 nm (YAG : Yb^{3 +} ), and 1064 nm (YAG : Nd^{3 +} ) in the temperature range 50°C to 600°C. Additionally, we offered a method to eliminate influence of vibration on accuracy of temperature measurements by adding SiO₂ sol to powders after their synthesis in sensitive elements.