Structural Health Monitoring System using Active Ultrasonic Nodes Powered by Optical Fiber

Structural health monitoring (SHM) offers extended structural lifespan, cost savings, and early risk detection, ultimately contributing to enhanced overall performance of critical structures. This paper presents a multiplexed active ultrasonic node for generating ultrasonic waves using a piezoelectric transducer powered by a single optical fiber (driven by a tunable laser) towards distributed SHM with no complex wiring. The proof-of-concept prototype is built using commercial off-the-shelf components on a 41×33 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> printed circuit board. In measurements, 2.75 mW of power is harvested by two parallelly connected Germanium photodiodes across a portion of the optical fiber with long period fiber Bragg grating at 1554 nm wavelength. This power is used to drive a piezoelectric transducer by five ~ 30 V pulses at 500 kHz. A method to program the number of driving pulses is also presented. Power scheduling technique ensures operation with limited available input voltage and power of hundreds of mV and a few mW, respectively.