Er3+/Yb3+ co-doped phosphate glass microsphere lasers have been studied under pumping by a fiber taper at 1480 nm. Whispering Gallery Mode laser spectra were analyzed for different sphere diameters. The gain spectrum is calculated for the transition 4I13/2 → 4I15/2 around 1550 nm. Red-shift effect on the wavelengths of both fluorescence and laser spectra is experimentally observed when the pump power is increased, originating from thermal effects. We showed coupling effect between microspherical laser and an external cavity made by a metallic mirror. We observed line shift to lower wavelengths due to optical feedback effect.