Single wavelength pump–probe technique to measure population recovery in a continuously pumped fiber amplifier

We report a single wavelength pump–probe technique that is used to measure population recovery in a continuously pumped fiber amplifier. Pump and probe pulse pairs were generated by a single laser diode modulated by a function generator. The dependence of the population inversion on the pulse interval was calculated from the amplified pulse shapes. Two recovery times, of the orders of a microsecond and a 100 µs, were clearly observed.