Dual-wavelength pumped thulium-doped optical fiber amplifier

34 34 32 34 34 An arrangement and method provide an optical thulium doped fiber amplifier utilizing a dual wavelength pumping scheme for amplifying an optical signal. The method includes the steps of: a first deposition (a) of energy into the fiber amplifier by pumping with radiation of a first wavelength; and a second deposition (b) of energy into the fiber amplifier by pumping with radiation of a second wavelength. The radiation of the first wavelength is arranged to induce, by single photon absorption, a population to the Hlevel of the thulium dopant, and the radiation of the second wavelength primarily depopulates the Flevel, by excited absorption of a single photon, preferably by strong excited state absorption to the Flevel. The steps gives a population inversion between the Hand the Flevels and facilitate a power efficient high gain amplification.