A Raman amplifier having a microstructured fiber and at least one pump laser, optically connected to one end of the microstructured fiber. The pump laser is adapted for emitting a pump radiation at a wavelength .lamda..sub.p, and the microstructured fiber has a silica-based core surrounded by a plurality of capillary voids extending in the axial direction of the fiber. The core of microstructured fiber has at least one dopant added to silica, the dopant being suitable for enhancing Raman effect.