We report results of transient two-wave mixing (TWM) in Er-doped fibers with saturable absorption in a linear configuration of an adaptive interferometric vibrometer with essentially different powers of recording waves. The TWM signal modulation depth detected in the weak (reflected) wave was shown to be twice as strong as in the symmetric configuration with equal recording powers. In accordance with theoretical predictions, the experimentally observed TWM signal amplitude grew continuously with the fiber optical density in the whole investigated range of . At the recording wavelength it proved to be quite close to the theoretical limit of for weakly absorbing fibers, and in -long fiber of high optical density reached maximal value of . The TWM response time went down with the recording light power and for was in the submillisecond region.
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