The absorption spectra of Er

3+

ion and Yb

3+

ion in tellurite glass were investigated. The peak absorption were marked according to the absorption transition of Er

3+

and Yb

3+

the energy levels of Er

3+

and Yb

3+

ions in tellurite glass were obtained according to the absorption spectra. The emission spectrum of Er

3+

ion in tellurite glass was studied. The stimulated emission cross section was calculated using McCumber theory and the FWHM was obtained according to the emission spectrum. Er

3+

ion show higher emission cross section(σp=7.5×10

-21

cm

2

) and larger FWHM (FWHM=66nm) in tellurite glass than those in other glass hosts

which are very important parameters for optical amplifiers to realize broadband and high gain amplification. The upconversion spectra of Er

3+

ion in tellurite glasses were measured and analyzed. The much lower phonon energy of tellurite glass makes it has different upconversion mechanism compared with other glasses with relative higher phonon energy. The relative longer lifetime of

4

I

11/2

level of Er

3+

ion in tellurite glass produces the upconversion process

4

I

11/2

+

4

I

11/2

→

4

F

7/2

+

4

I

15/2

much more serious

and the four emission transitions

4

F

7/2

→

4

I

15/2

2

H

11/2

→

4

I

15/2

4

S

3/2

→

4

I

15/2

and

4

F

9/2

→

4

I

15/2

which corresponds to 486

530

550.and 660nm emission

respectively

become obvious. Furthermore

the upconversion intensity enhances with the increase of Yb

3+

concentration. Upconversion emission is very harmful for fiber amplifiers

which not only reduces the efficiency of bump light

but also deteriorates the noise figure of the amplifiers

so it is important to reduce upconversion phenomenon as much as possible. The energy transfer mechanism between Er

3+

and Yb

3+

ion were analyzed. The energy transfer coefficients and efficiencies between Yb

3+

and Er

3+

were calculated. At a certain Yb

3+

concentration

the forward energy transfer coefficient and efficiency hardly change while the back energy transfer coefficient and efficiency increase monotonically. So the effective sensitization of Yb

3+

to Er

3+

is appropriate only at a certain range of Yb

3+

concentration. The right selection of Yb

3+

concentration is needed in order to realize effective bump.