Excited states Tm spectroscopy in ZBLAN glass for S-band amplifier Ste ´phan Guy * , A.M. Jurdyc, Bernard Jacquier, W.M. Meffre Laboratoire de Physico-Chimie des Mate ´riaux Luminescents; Univ. Lyon 1, UMR n°5620 du CNRS, Domaine Scientifique de la Doua, 10, rue Andre ´-Marie Ampe `re, 69622 Villeurbanne Cedex, France Received 7 January 2005; received in revised form 17 February 2005; accepted 17 February 2005 Abstract We report on excited state spectroscopy measurements of Tm doped ZBLAN glass designed for fiber amplifier in the 1.48 lm wavelength range. Low temperature absorption, emission and Excited State Excitation measurements are reported to clearly identify the transitions involved in the different pump mechanisms of this Thulium Doped Fluoride fiber Amplifier. Room and low temperature Excited State Absorption spectra were recorded and quantitative determi- nation of absorption cross sections has been obtained which allows to further proceed to a modeling of this amplifier. Ó 2005 Elsevier B.V. All rights reserved. PACS: 78.20.e; 78.20.Ci; 32.70.n Keywords: Excited state spectroscopy; Thulium doped amplifier; Fluoride glasses 1. Introduction Exponential growth of data and voice traffics in telecommunications raises the question of the limit of the actual capacity of optical fiber. A first way to improve the communication capacity is to in- crease the channel bit rate. Unfortunately, above a few GBits/s, chromatic dispersion as well as non- linear effect are no more negligible leading to much more complex transmission. Wavelength Division Multiplexing across the two amplification bands C and L of erbium gain emission have consider- ably pushed away this limit [1]. There are not so many solutions to increase this capacity again: re- duce spacing between channels (or wavelengths), increase broadening of the erbium emission and finally open new amplification bands. The two for- mer solutions are already limited by wavelength selectivity of filter devices and glass composition respectively, then the latter proposal offers more 0030-4018/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.optcom.2005.02.058 * Corresponding author. Tel.: +33 4 72 43 12 08; fax: +33 4 72 43 11 30. E-mail address: guy@pcml.univ-lyon1.fr (S. Guy). Optics Communications 250 (2005) 344–354 www.elsevier.com/locate/optcom