Rare-earth-doped glasses for fiber amplifiers in broadband telecommunication

Rare-earth-doped optical amplifiers have a great potential for broadband Wavelength-Division-Multiplexed (WDM) telecommunication by tailoring host glass compositions. In order to design the emission spectra of doped rare-earth ions, it is important to understand the relationship between the local ligand field and various optical properties of specific 4f-levels, such as the radiative transition probability, the nonradiative decay probability, which dominate the spectral line width and quantum efficiency of amplification transitions. For the Er3+:1.55 mum transition, the role of the Judd-Ofelt Omega(6) parameters is presented, which is correlated to the Er-ligand bond covalency in glasses. The Tm3+: 1.46-mum transition shows quantum efficiency over 90% high enough for the S-band application, in heavy metal oxide glasses with moderate phonon energy and wider spectra than fluorides. A way to improve population inversion by selective energy transfer with codoped lanthanide ions is presented. Finally, the energy level structures and resultant spectral properties of Pr3+, Nd3+ and Dy3+ ions, 1.3-mum-active ions, are compared. The hypersensitivity of Dy3+ transitions appears especially in chalcogenide glasses, where the nonradiative loss due to multiphonon decay is also minimized. In conclusion, glass materials have opportunities to vary the radiative cross section, quantum efficiency, and gain flatness, which are important for novel amplifiers in the future DWDM system. (C) 2002 Academie des sciences / Editions scientifiques et medicales Elsevier SAS.