In-line gain control of the erbium doped fiber amplifier using samarium doped inner-cladding in the 1.5 /spl mu/m region

A new type of erbium doped fiber for optical amplifier was reported where erbium was doped in the center of the core and samarium doped in a ring in the cladding. By utilizing the spectral overlap of the absorption cross section of samarium in the inner-cladding and the emission cross section of erbium ion in the core, we demonstrated a new way of in-line control the gain spectrum of erbium doped amplifier pumped at 980 nm. The gain spectra in the conventional band were measured and we demonstrated potential of gain-flattening in the 1.5 mm region without external filters using the specially designed fiber. The effects of samarium doped inner-cladding on amplified spontaneous emission in the long band were also reported.