In this paper we present a fiber-optic vibrometer which can be used as a microphone unit for totally implantable hearing aids (TIHA). The basic principle of operation is low coherence interferometry realised in the form of miniaturised fiber-optic microphone with only one sensing fiber directed to the oscillating target. We have been using this system for contactless investigation of the rabbit middle ear. The vibrations of the incus were investigated from 200 Hz to 10 kHz under the sound intensities in the range of 70 to 90 dB. All measurements were obtained for about 200 μm distance between the incus and sensing fiber which enables continuous functionality of the system even in the case of large quasistatic movements of auditory ossciles.
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