THE ERBIUM-DOPED fiber amplifier (EDFA) has been
highly successful as a low-noise gain block at 1535-nm
wavelength. Er-doped waveguide amplifiers (EDWAs) have
also attracted attention, because of their potential for integration
with pump lasers and filters [1]. The main difficulty in
constructing an EDWA lies in providing suitably high gain
in a short length, which requires high Er doping without
concentration-dependent effects