Myotis 1300

Undetectable Optical Microphone

Phonoptics is proud to introduce the world’s first optical microphone using a single optical fiber. Until now, microphones have relied on electrical components: a moving magnet in a coil for dynamic microphones, a capacitor for electrostatic microphones, and many others. Unfortunately, these designs prevent their use in harsh environments that can damage equipment or simply disrupt the electrical signal. Additionally, recordings can only be made at short range.

By using an optical fiber, Phonoptics has successfully designed a microphone that overcomes these limitations. Optical fiber is naturally resistant to electromagnetic fields, extreme temperatures, and external pressures. Emitting no signal, the microphone is therefore undetectable. Thanks to the low signal attenuation in optical fiber, the Phonoptics microphone can be used several kilometers away from the control station.

Phonoptics’ patented technology is based on using a single optical fiber. This enhances both robustness and ease of use.

What difference does a single optical fiber make?

Normally, one fiber is needed for the outbound signal and another for the return signal. Phonoptics’ technology eliminates this constraint by transmitting both outbound and return signals through the same optical fiber. Using a single fiber simplifies manufacturing and operation of the product:

• In case of a splice or accidental break, repair is quick and easy thanks to widely available professional fusion splicers. There’s no risk of confusing the transmit and receive fibers.

• Single-fiber connectors are far less expensive than dual-fiber ones.

• It’s impossible to connect the fiber incorrectly to the housing.

• For long distances, the cost per meter is lower.

• Twice as miniaturizable: in an integrated system, it’s possible to use a bare fiber just 250 µm thick.

• Simplified installation and cost for creating a sealed feedthrough.
  

Is an optical fiber fragile?

It’s commonly thought that an optical fiber is fragile. However, one must remember that the melting point of glass is around 800 °C, and a simple 200-micron-diameter fiber can withstand a 5 kg tensile load, making it actually a robust material. The real weakness comes from bending. That’s why several types of coatings have been developed to allow optical fibers to endure tight bends: Kevlar, polyimides, HCS polymer, and many others. Thanks to these coatings, some fibers can tolerate a bending radius as small as 7.5 mm with only 0.2 dB of loss.