  Rare earth (RE) doped silica-based optical fibers with transparent glass
ceramic (TGC) core was fabricated through the well-known modified chemical
vapor deposition (MCVD) process without going through the commonly used stage
of post-ceramming. The main characteristics of the RE-doped oxyde nanoparticles
namely, their density and mean diameter in the fibers are dictated by the
concentration of alkaline earth element used as phase separating agent.
Magnesium and erbium co-doped fibers were fabricated. Optical transmission in
term of loss due to scattering as well as some spectroscopic characteristics of
the erbium ions was studied. For low Mg content, nano-scale particles could be
grown with and relatively low scattering losses were obtained, whereas large
Mg-content causes the growth of larger particles resulting in much higher loss.
However in the latter case, certain interesting alteration of the spectroscopic
properties of the erbium ions were observed. These initial studies should be
useful in incorporating new doped materials in order to realize active optical
fibers for constructing lasers and amplifiers.
