Crosstalk in 1.3 mu m praseodymium fluoride fiber amplifiers

Praseodymium-doped fluoride fiber amplifiers have been demonstrated to provide good gain, output power, and noise performance in the second telecommunications window. This paper presents a study of the crosstalk performance of these amplifiers. A theoretical analysis is presented from which a numerical model is developed and is used to predict the crosstalk performance of a typical amplifier. Experimental results, using two separate signals within the gain band, show good agreement between measurement and theory, indicating that it is unlikely that crosstalk will present a problem in anticipated amplifier applications. From the measured crosstalk, an upper limit is placed on the lower level lifetime, indicating that the population of this level will have a negligible effect amplifier gain. A novel technique for measuring the upper state lifetime in an amplifier, based on pump power dependence of crosstalk, is described and experimental results which are in agreement with fluorescent decay are presented.