Investigation and Development of a Fiber-Optic Vibrometer for Use in Totally Implantable Hearing Aids

In this paper we present the results of the research and development of a fiber-optic-based vibrometer for use in totally implantable hearing aids (TIHAs). We addressed the most important issues regarding the projected vibrometer: the optoelectronic measurement technique and signal processing, the optomechanical positioning of the sensing fiber, the surgical implantation technique and the material's biocompatibility. We performed in-vitro and in-vivo measurements of the target (e.g., incur) vibrations with a sub-nanometer resolution over the whole audio range, using low and/or high coherence techniques. A breakthrough is made by a dramatic reduction of the power consumption of the optoelectronic and signal-processing unit to about 2 mA at 2.2 VDC by introducing a digital signal processing (DSP) technique.