High power laser are a key ingredient of the future GWDs. It is obviously a technology having a crucial industrial potential, although the requirements imposed by GW experiments, in terms of low noise and stability, are well beyond what usually requested by industrial applications. For the third generation of GWDs, not only laser sources at 1μm but also at 1.55μm will be needed. The current laser technology developed for the laser systems for the second, advanced generation of GWDs relies on well-established Nd-doped solid state laser technology. However, the change to the 1.55μm wavelength region implies also a change not also of the active dopant but also the underlying laser technology. In particular, the 1.55μm wavelength range can be mainly addressed using Er3+-ions active dopant. Furthermore, Er-doped fibres offer the most promising way to date to realize high-power, high-brightness laser sources at 1.55μm.