Adapting Mach-Zehnder Interferometers for Vibration Sensing

Abstract

Silicon photonic sensors are superior alternatives to traditional electromechanical sensors in applications such as vibration monitoring of data center buildings or real-time seismic wave detection at underwater fiber optic network sites. Because they communicate using optical signals, these sensors can be seamlessly integrated into a data center’s existing architecture, or underwater fiber optic networks. Their immunity to electromagnetic field interference and ability to withstand harsh environments also contribute to the suitability of these optical sensors for implementation in the nuclear energy industry and power management facilities. The Mach-Zehnder Interferometer (MZI) is an optical component that operates based on the constructive and destructive interference of light passing through its two arms. This component is usually used for electro-optical modulation in telecommunication. By allowing one of its arms to vibrate freely on a silicon chip, the MZI can also function as an accelerometer. In an MZI accelerometer, the output light power and free spectral range (FSR) correlate with applied vibration. Only, measuring the output power of an MZI at its optical resonance frequencies and/or measuring its FSR in real-time is a challenging task. We propose two modifications to resolve this issue. The first is to create an imbalance to the MZI by increasing the fixed arm length. The resulting MZI responds to applied vibration through changes in the FSR, which can be easily measured using peak-detection. The second modification involves adding a heater as an optical modulator on the fixed arm. A closed loop feedback controller can then be used to apply enough power (heat) to compensate for the vibration of the freestanding arm. The magnitude of applied power correlates with the acceleration. The proposed modifications to the MZI will enable more straightforward and efficient measurement of acceleration using silicon photonic sensors, making them an even more versatile option for a wider range of applications.