The Wisdom of Light in a World of Noise
Optoacoustics’ award-winning sensor technology uses photonic principles to precisely measure sound, vibration, pressure and other key physical characteristics in locations where conventional sensors cannot be used.
Our fiber optical sensors and sensing systems provide safe, high performance, and reliable service as microphones, headphones, noise-cancelling devices, accelerometers and pressure sensors in the world’s most difficult and demanding applications.
Optoacoustics’ portfolio of patented technologies offers the following advantages:
- Complete EMI/RFI immunity
- High signal quality
- Extremely high sensitivity at very low frequencies
- Optical data connection over very long distances without signal loss
- Low total harmonic distortion (THD)
- Lightweight, designed for custom mounting
- High signal-to-noise ratio (SNR)
- Long term reliability and stability
Optoacoustics optical fiber sensor design is based on our patented core sensor, an advanced MEMS membrane and a separate electro-optic subsystem.
Core Sensor Platform
Optoacoustics’ core platform is built on an optical sensor that can measure changes in light intensity reflected from a tiny membrane embedded at its center.
These changes occur when acoustic waves collide with the membrane and cause it to vibrate. Our platform passively detects membrane displacement at sub-angstrom resolutions, so even minute changes can be detected and measured very precisely using optics and simple electronic processing. The result is a true-to-source signal that can be amplified or analyzed further without any loss of quality.
The sensing path begins with light produced by a LED which travels over an optical fiber to the optical head, and is beamed onto the ultra-sensitive membrane. When the membrane vibrates, the intensity of the light it reflects changes, providing a basis for dynamic measurement. Reflected light travels over a second optical fiber to a photo detector, which produces the intensity-modulated data for signal processing.
Optoacoustics’ core platform contains no electronic components — the processing is performed in a subsystem that can reside at an ideal distance from the sensor. Using optical fiber for transmission ensures that membrane modulation data is not compromised, even at distances of over a kilometer.
Device sensitivity is determined by the intensity of light reflected off the vibrating membrane, and is controlled by two factors: the angle of the two optical fibers, and the distance from the membrane to the optical head. As the membrane moves away from the optical head, a greater amount of reflected light is collected by the second fiber. The amount of transferred light can increase until it reaches its maximum in terms of the optical fiber geometry. After this maximum light intensity is reached, a further increase in distance between the membrane and the optical head will result in a gradual decrease in the amount of reflected light collected.
Sensitivity calculations take each of these factors into account - along with the sensing application environment - to arrive at the optimum geometric arrangement and power levels.
Advanced MEMS Membrane
At the heart of Optoacoustics’ extraordinary fiber optic sensor is our ultra sensitive reflective membrane, a product of advanced micro-electro mechanical systems (MEMS) technology. The active area of this extremely thin membrane is composed of low stress silicon nitride, engineered with numerous circular corrugations to increase its sensitivity. At its center is a tiny gold dot, which serves as the surface that receives and reflects light.
During operation, this gold dot is the pinpoint for all measurements, making it possible to adjust both sensitivity and signal-to-noise response by dynamically changing the intensity of light transmitted by the source LED.
Here also, since no electronic components are used to produce a signal, electromagnetic interference (EMI) and radio frequency interference (RFI) are not a factor in sensor performance.
Membrane Linear Response
This proprietary membrane experiences a smooth linear response with a dynamic range of 100 dB. Optoacoustics has designed each of the following critical membrane parameters to optimize sensor performance:
- Membrane layer materials (Young modulus)
- Membrane layer residual stress
- Membrane layer thickness
- Membrane size
- Corrugation profile and depth
- Gold dot reflectivity to IR
- Gold dot residual stress
A separate electro-optic unit (EOU) houses the LED and photo detector components, as well as an analog electronic processing circuit.
The electronic circuit is comprised of a trans-impedance circuit and conditioning amplifier and performs all required signal amplification and processing, eliminating the need for additional devices. Our EOU also ensures that sensor performance - including application-critical characteristics such as frequency response and sensitivity - is optimized at all times.
Fully utilizing Optoacoustics' core fiber optic sensor technology, the EOU can be located at great distances from the application environment, and so does not pose a safety risk or create a new source for EMI/RFI.
Our comprehensive selection of EOUs offers a wide variety of subsystem capabilities and packaging, adaptable to every application and environment.