Tm3+-doped glasses have two emission bands that peak around 1470 nm and 1800 nm in the near infrared, making them potentially important in the development of fiber-optic amplifiers and fiber lasers. The relative strength and the quantum efficiency of these bands depend on the glass composition as well as the active ion concentration. In this study, we have investigated the variation of the luminescence strengths as a function of glass composition and Tm3+ ion concentration in a new type of Tm3+-doped tellurite glass. In the experiments, two sets of samples with the host composition (1-x)TeO2-(x)PbF2 were prepared. In the first set, the active ion concentration was constant (1 mol. % Tm3+) and x=10, 15, 17, 20, 22 and 25 mol. %. The second set had samples with x=10 mol. % and the active ion concentration varied from 0.2 to 1 mol. %. In the experiments, absorption measurements were first made to determine the spontaneous emission probabilities of the 4f-4f transitions of the Tm3+ ions. The calculations were made by using the Judd-Ofelt theory. The samples were then excited with a 785-nm diode to measure the relative emission strengths of the 1470-nm and 1800-nm bands. Our results show that as the Tm3+ ion concentration increases from 0.2 mol. % to 1 mol. %, the ratio of the 1470-nm intensity decreases from 0.98 to 0.18 relative to that of the 1800-nm band.