Analysis of gain dynamics in Pr/sup 3+/-doped fluoride fiber amplifiers

A large-signal model for a four-level laser system which includes time variation effects has been used to study low frequency response characteristics, two-channel crosstalk and transient effects in praseodymium-doped fluoride fiber amplifiers (PDFFA). Pump power modulation results in a low-pass transfer of modulation to signals amplified in the PDFFA. Low-frequency compression of the PDFFA input/output signal transfer characteristic has been observed. Due to a relatively long lifetime of the /sup 1/G/sub 4/ metastable level, multichannel crosstalk lower than 30 dB has been calculated for modulation frequencies higher than 600 kHz. Response of the PDFFA toward a low-frequency signal square pulse exhibits a characteristic overshoot that originates from the PDFFA saturation by the amplified signal.<>