Acoustic Emission Sensor for Spacecraft Applications

Los Gatos Research proposes to develop a new Bragg grating-based acoustic emission (AE) sensor technology consisting of optical fibers, integrated optical waveguides, and an on-chip optical demodulation device system. Compared with conventional optical fiber based sensor systems, our technology offers substantially higher sensitivity. We achieve this by combining the mature Bragg grating technology with the inherently high sensitivity of polymer waveguides to stress waves. Using a hybrid silica/polymer Bragg grating multiplexing scheme, the sensor system is capable of simultaneously measuring temperature and strain/stress. By integrating optical waveguide filters and couplers with the Bragg grating array sensor, the sensor system offers increased dynamic range for simultaneous detection of both the high and low energy AE signals arisen during impact or crack formation. The Phase I research has demonstrated the feasibility of the integrated polymer waveguide and Bragg grating fabrication technology and the use of Bragg gratings for static and dynamic stress sensing. In the Phase II research effort, the polymer waveguide and Bragg grating designs will be further optimized. Hybrid polymer/silica Bragg grating array and an on-chip wavelength filter demodulation prototype system will be developed for temperature, stress/strain, and AE detection and location measurements.