Recent studies on optical properties of Tm3+-doped tellurite glasses are presented as candidate materials of 1.4 micrometers amplifier. Usually, non-oxide fiber hosts with lower phonon energy are required, because the initial 3H4 level is easily quenched in high-phonon-energy environment. However, the restriction is not so server as that of the Pr3+:1G4 for 1.3(Mu) M amplifiers due to the moderate energy gap. The Judd-Ofelt analysis showed 96 percent quantum efficiency in a tellurite host. To overcome the problem of intensity amplified spontaneous emission of competitive 0.80micrometers transition from the initial 3H4 level, an Nd-doped cladding was proposed utilizing a strong absorption band. Improved emission was obtained as a result of radiative energy transfers between Tm3+ and Nd3+ ion. Also, the effect of codopants, such as Eu3+, Tb3+, Ho3+, on the lifetime of the Tm3+-levels was investigated for efficient population inversion between the 3H4 and 3F4. The Ho3+ showed the best selectivity in quenching effect. Owing to its quantum efficiency and better fiberizability than fluorides, the Tm-doped tellurite glass can be a potential candidate of the amplifier at the S+-band in the WDM telecommunication.