EVALUATION OF PARASITIC UP-CONVERSION MECHANISMS IN ER3-DOPED SILICA-CLASS FIBERS BY ANALYSIS OF FLUORESCENCE AT 980 NM()

The behavior of modulated and unmodulated upconversion fluorescence in Er3+-doped silica-glass optical fibers pumped at 1480 nm has been exp erimentally and theoretically investigated. It is found to be consiste nt with a model where the upconversion fluorescence is generated by ho mogeneous and inhomogeneous energy-transfer upconversion. Model calcul ations indicate an upper limit of a homogeneous upconversion coefficie nt of 10(-23) m(3)/s in a fiber, and a negligible cross-section for ex cited-state absorption at 1480 nm.