Serially multiplexed dual-point fiber-optic acoustic emission sensor

Development of a serially multiplexed fiber-optic acoustic emission (AE) sensor is described. The sensor detects AE events in real time at two different points along the length of an optical fiber. The time-domain waveform contains signals from the two locations, and a method is introduced for identification of the signals. Detection and identification of signals along a single data stream reduces the data-acquisition rigor and provides for rapid real-time damage location detection in materials. The sensor consists of two optical fiber coils along an arbitrary length in a Michelson interferometer arrangement. The formulations involve the methodology for tagging of the time-domain signals. The process leads to matching of the arrival times in the waveform to the individual coils along the length of the optical fiber. The waveform is detected at the quadrature point for maximum sensitivity. A bias is created through differentiation and superposition of the waveform to accomplish signal identification. The experimental program involved proof of concept tests by way of damage location detection along the lengths of individual composite rods. Conventional piezoelectric transducers were also employed for comparison of results.