ANALYSIS OF GAIN IMPROVEMENT OF PR3-DOPED FLUORIDE FIBER AMPLIFIERS USING AN OPTICAL FILTER OR ISOLATOR()

The possibility of improving the gain and noise figure of a Pr3+-doped fluoride fibre amplifier by insertion of an optical narrow band-pass filter or an isolator within the praseodymium-doped fibre has been stu died using a comprehensive large-signal numerical model. Three pumping schemes, codirectional, counterdirectional and bidirectional pumping, have been investigated. It follows from the analysis that a gain impr ovement as high as 8.5 dB can be achieved for a bidrectionally pumped amplifier with an inserted filter compared to the bidirectionally pump ed PDFFA without filter. The optimum filter/isolator position for the bidirectionally pumped PDFFA has been found to be in the middle of the active fibre length. For codirectional and counterdirectional pumping , the optimum filter/isolator position varies with the pump power.