Optical gain characteristics of an Er3+‐doped silica fiber have been studied by end pumping with a 1.48 &mgr;m InGaAsP high‐power laser diode. A gain as high as 12.5 dB was obtained for an absorbed pump power of 16 mW with a 3‐m‐long fiber. By constructing an Er3+fiber ring cavity with a 3 dB single‐mode fiber coupler, we have obtained continuous wave laser oscillation at a wavelength of 1.553 &mgr;m.