An optical fiber including: (i) a silica based, rare earth doped core having a first index of refraction n.sub.1; and (ii) at least one silica based cladding surrounding the core and having a second index of refraction n.sub.2, such that n.sub.1>n.sub.2, said cladding having a plurality of stress rods and a plurality of air holes extending longitudinally through the length of said optical fiber; wherein said optical fiber supports a single polarization mode or poses-polarization maintaining properties within the operating wavelength range.