An optical fiber that includes a core containing a first concentration of germanium, an inner cladding arranged on the core, the inner cladding containing a second concentration of germanium and having a first diffusion coefficient, and an outer cladding arranged on the inner cladding, the outer cladding having a second diffusion coefficient, where the first diffusion coefficient is larger than the second diffusion coefficient, and where the first concentration of germanium is about 200% or more of the second concentration of germanium. An optical fiber constructed in this manner can be spliced with an optical fiber having a different MFD, such as a single-mode optical fiber or an erbium-doped optical fiber, with low splice loss and a sufficient splicing strength.