We present a review on recent progress in the research and development of nanoparticlecontaining optical fibers for high-power fiber lasers, amplifiers, and ASE sources. Attention has been focused on rare-earth-doped silica fibers with nanoparticles in the core. Progress in materials, technologies, characterization techniques, and achievements has been summarized. Materials of active fibers based on yttrium-aluminium silicates, mullite, protoenstatite, and phosphates doped with Er3+, Yb 3+, Eu3+, and Tm3+ have been reviewed. The material research in this field has been systematically investigated by research groups from ORC Southampton, CGCRI Kolkata, LPMC Nice together with CNR-IOM-OGG Grenoble, nLIGHT (formerly Liekki), and IPE Prague since 2007. The best slope efficiency achieved with Yb –doped nanoparticle-containing fiber was in the range of 70-80 %.