Fiber-Optic Interferometry for Rapid Pressure or Magnetic Sensing

We report the design, construction, and use of several fiber-optic-based sensors: 1) a fast pressure sensor, measuring the deflection of a metallic membrane; 2) a compact, rapid magnetic sensor; and 3) a compact piezo-driven micro-oscillator. For 1), we apply the linear plate bending equation to determine the effective spring constant of a membrane; for a 150 µm stainless steel membrane, k = 4.5 * 10⁶ N/m (and its resonance frequency f₀ = 109 kHz), ensuring a fast time resolution (~10 µs) for rapid pressure measurement. Initial measurements agree with the predicted displacement sensitivity of ~0.18 µm/atm. Similiarly, for a 100 μm platinum membrane, k = 1.2 * 10⁶ N/m with a resonance frequency f₀ = 42 kHz and time resolution of ~24 μs. The predicted displacement sensitivity of ~0.68 μm/atm has been confirmed by initial measurements. For 2) and 3), we are integrating micro-oscillators directly onto optical fibers, for magnetic and piezo-driven sensing, respectively. Future work for 1) will involve dual interferometers to determine pressure and temperature simultaneously. For 2) and 3), encapsulation will be explored to utilize the sensors in application.