An optical fiber amplifying system, the optical fiber amplifying system providing amplified optical radiation having a first amplified wavelength, the optical fiber amplifying system comprising: an optical source having an output, the optical source being configured to provide radiation of the first amplified wavelength and comprising: one or more first amplifying stages together having an output, each of the one or more first amplifying stages comprising a first active optical fiber, the first active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of a pump wavelength; and one or more first optical pump sources, each configured to output radiation of the pump wavelength, each operatively coupled to one or more of the first active optical fibers of the first amplifying stages; an intermediate stage having an input operatively coupled to the output of the optical source and an output, the intermediate stage comprising an intermediate active optical fiber having an amplified wavelength that is the same as the first amplified wavelength and a first pump wavelength; a final amplifying stage having an input coupled to the output of the intermediate stage and an output, the final amplifying stage comprising a final active optical fiber, the final active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of the first pump wavelength; and one or more final optical pump sources together operatively coupled to the final active optical fiber and the intermediate active optical fiber and configured to output radiation of the first pump wavelength, the one or more final optical pump sources being configured to be driven by a common voltage source, characterized in that the one or more final optical pump sources are configured to be switched together, separately from the one or more first optical pump sources, between a low power state sufficient to render the intermediate stage less than about 10% transmissive to radiation of the first amplified wavelength, and a high power state sufficient to render the intermediate stage more than about 80% transmissive to radiation of the first amplified wavelength. an optical source having an output, the optical source being configured to provide radiation of the first amplified wavelength and comprising: one or more first amplifying stages together having an output, each of the one or more first amplifying stages comprising a first active optical fiber, the first active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of a pump wavelength; and one or more first optical pump sources, each configured to output radiation of the pump wavelength, each operatively coupled to one or more of the first active optical fibers of the first amplifying stages; one or more first amplifying stages together having an output, each of the one or more first amplifying stages comprising a first active optical fiber, the first active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of a pump wavelength; and the one or more first amplifying stages comprising a first active optical fiber, the first active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of a pump wavelength; and one or more first optical pump sources, each configured to output radiation of the pump wavelength, each operatively coupled to one or more of the first active optical fibers of the first amplifying stages; an intermediate stage having an input operatively coupled to the output of the optical source and an output, the intermediate stage comprising an intermediate active optical fiber having an amplified wavelength that is the same as the first amplified wavelength and a first pump wavelength; a final amplifying stage having an input coupled to the output of the intermediate stage and an output, the final amplifying stage comprising a final active optical fiber, the final active optical fiber being configured to amplify radiation at the first amplified wavelength when pumped with pump radiation of the first pump wavelength; and one or more final optical pump sources together operatively coupled to the final active optical fiber and the intermediate active optical fiber and configured to output radiation of the first pump wavelength, the one or more final optical pump sources being configured to be driven by a common voltage source, characterized in that the one or more final optical pump sources are configured to be switched together, separately from the one or more first optical pump sources, between a low power state sufficient to render the intermediate stage less than about 10% transmissive to radiation of the first amplified wavelength, and a high power state sufficient to render the intermediate stage more than about 80% transmissive to radiation of the first amplified wavelength.