Nd3+-doped 1.3micrometers fiber amplifier has many inherent advantages, but two major problems must be overcome to achieve a device: signal excited-state absorption (ESA), and amplified spontaneous emission (ASE). Signal ESA around 1300 nm prevents gain in that region, and so red-shifts and gain out of the second telecom window. The ASE at 1050 nm has a branching ratio 5 time larger than the 1.3 micrometers transition; as a result it clamps signal gain at low values. Moreover, in many Nd3+-doped glass hosts the peak of emission lies at wavelengths above 1320 nm. In this paper we present new highly ionic fluoroaluminate glasses developed as hosts for the 1.3 micrometers -doped fiber amplifier and discuss aspects of glass design. (Formula available in paper) emission peaks between 1310 and 1317 nm were demonstrated in bulk glasses, and gain in the 1310-1320 nm region was measured in fiber. The gain and emission spectra show evidence of significantly reduced ESA. ASE filtering is discussed, focusing on Bragg grating filters and on absorbing co-dopants, such as (formula available in paper) The paper also assesses thermal and viscous properties of the core and cladding glasses for fiber drawing.
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