Investigation of the inner ear is still the subject of basic research. The concept of an active filtering process in the mechano-electrical transfer mechanism in the inner ear (cochlea) was introduced. In this paper an optical approach detecting microvibrations is discussed. A fiber optic heterodyne interferometer with a miniaturized sensorhead was built. The fibers ensure flexibility and easy handling of the interferometer whereas the miniaturized sensorhead allows a non-invasive approach to the organ of Corti. In heterodyne interferometry as compared to classical interferometry two slightly different light frequencies for the reference and object beams are used. The vibration of the object is detected as a modulation of the phase of the detector signal. To obtain the information on the vibration two methods were analyzed and applied: namely measuring the amplitude of the sidebands in the spectrum of the modulated signal and secondly signal demodulation. It is possible to detect amplitudes down to 0.3 angstrom in a frequency range of 500 Hz to 50 kHz with a simulated object reflectivity of 0.02%.
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