What are Fiber optical microphones?

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The fiber optical microphone is an entirely new microphone concept, first invented in Israel in 1984 by Drs. Alexander Paritsky and Alexander Kots. Conversion of acoustical waves into electrical signals is achieved not by sensing changes in capacitance or magnetic fields (as with conventional microphones), but instead by sensing changes in light intensity. During operation, light from a laser source travels through an optical fiber to illuminate the surface of a tiny, sound-sensitive reflective diaphragm. Sound causes the diaphragm to vibrate, thereby minutely changing the intensity of the light it reflects. The modulated light is then transmitted over a second optical fiber to a photo detector, which transforms the intensity-modulated light into electrical signals for audio transmission or recording.

The fiber optical microphone has very specific advantages over conventional microphones. First, no electronic or metal components are used in the microphone head or the connecting fibers, so the microphone does not react to or influence any electrical, magnetic, electrostatic or radioactive fields (this is called EMI/RFI immunity). The fiber optical microphone is therefore ideal for use in areas where conventional microphones are ineffective or dangerous, such as inside industrial turbines or in magnetic resonance imaging (MRI) equipment environments. Another advantage is the physical nature of optical fiber light propagation. The distance between the microphone's light source and its photo detector may be up to several kilometers without need for any preamplifier and/or other electrical device. Finally, fiber optical microphones possess high dynamic and frequency range, similar to the best high fidelity conventional microphones. They are robust, resistant to environmental changes in heat and moisture, and are excellent for noise-canceling applications.

Fiber optical microphones can be produced for any directionality or impedance matching. They have proven especially useful in medical applications (with particular success in MRI patient-to-staff communications), audio calibration and measurement, industrial equipment sensing, high-fidelity recording and law enforcement. A comprehensive range of commercial fiber optical microphones is manufactured by Optoacoustics.

Source: wikipedia.com

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