Erbium-doped waveguide devices for WDM applications

We show that, if the limited gain of Er-doped waveguides makes them unsuitable as a replacement for EDFAs in straight amplifier roles, the very low threshold achievable with Yb co-doping allow their use in integrated configurations where gains of a few dB/cm are adequate, with the possibility of pumping several waveguides from a single 980 nm laser diode.