A 1.3 mu m-band optical amplifier includes an optical amplifying fiber doped with Yb ion for emitting light in 1.02 mu m band by pumping of the 0.98 mu m band light and Pr ion for amplifying signal light by pumping of the 1.02 mu m band light. Both ends of the optical amplifying fiber are connected to optical fiber gratings for selectively reflecting 1.02 mu m band light via matching connecting members and tapered core optical fibers. The optical fiber gratings form a 1.02 mu m-band resonator. A Wavelength Division Multiplexing (WDM) optical coupler multiplexes the signal light and pumping light from an pumping laser and supplies the thus-multiplexed light to the optical fiber grating. The pumping laser comprises a laser device which causes laser oscillation at 0.98 mu m. A 1.5 mu m-band optical amplifier having a similar configuration is also disclosed.
