Disclosed is an amplifying optical fiber for amplifying optical signal
transmitted therethrough by stimulated emission, the amplifying optical fiber comprising:
an inner core disposed at a center of said optical fiber and containing MX, GaS3/2
and RE; an outer core surrounding said inner core and containing SiO2;
and a cladding surrounding said outer core and containing SiO2, wherein
said M contained in MX is one component selected from the group consisting of Na,
K, Rb and Cs; said X contained in MX is one component selected from the group consisting
of F, Cl, Br, and I; and said RE is one component selected from the group consisting
of Ce, Pr, Pm, Nd, Sm, Eu, Gd, Tb, Ho, Dy, Er, Tm and Yb.
