We have quantitatively studied the energy-transfer processes between trivalent thulium ions in aluminate glass with different ${\mathrm{Tm}}^{3+}$ concentrations. Our emphasis has been placed on the determination of the microscopic and macroscopic parameters—the critical radius of these energy transfer processes, i.e., cross relaxation $({}^3\mathrm{H}_4+{}^3\mathrm{H}_6\to {}^3\mathrm{F}_4+{}^3\mathrm{F}_4)$ and donor–donor energy migration $({}^3\mathrm{H}_4+{}^3\mathrm{H}_6\to {}^3\mathrm{H}_4+{}^3\mathrm{H}_6)$ . For the $1.8\mu \mathrm{m}$ emission in aluminate glass, only a slightly slower increase rather than quenching, even at a high concentration (higher than $15\mathrm{wt}\mathrm{\%}$ ), was observed. Quantitative evidences and explanations indicated that high-order multipolar coupling mechanisms played an important role in energy transfer processes, and it would be helpful to predict efficient host materials and impurity concentrations according to these results to prevent the depopulation of the ${}^3\mathrm{F}_4$ energy level.