We report on the frist experimental demonstration of a scalable fiber laser approach based on phase-locking multiple gain cores in an antiguided structure. A novel fabrication technology is used with soft glass components to construct the multie core fiber used in our experiments. The waveguide region is rectangular in shape and comprised of a periodic sequence of gain and no-gain segments having nearly uniform refractive index. The rectangular waveguide is itself embedded in a lower refractive index cladding region. Experimental resutls confirm taht our five-core Nd doped glass prototyep structure runs predominately in two spatial antiguided modes as predicted by our modeling.