Masahito Ishioka

Aircraft Structural Health Monitoring using on-board BOCDA system

We developed the on-board BOCDA system for airplane and verified the flight environmental stability and durability through environmental test. The on-board BOCDA system adopted the polarization diversity technique and temporal gating technique to improve robustness of the BOCDA system. We successfully measured distribution of fiber Brillouin gain spectrum over 500m measurement range with 50mm spatial resolution, 60Hz sampling rate and ±13μ strain accuracy. Furthermore, we considered flight test to verify the validity of the BOCDA system. From these results, it was confirmed that BOCDA system has potential to be applied to an aircraft structure health monitoring system.

An application test using Brillouin optical correlation base analysis method for aircraft structural health monitoring

The authors developed a prototype Brillouin measurement system and carried out some application tests to verify the capability for aircraft structural health monitoring (SHM). The prototype Brillouin measurement system is adopted the Brillouin optical correlation domain analysis (BOCDA) method. This system is able to measure the distribute strain of full-length optical fiber sensor with 50mm of spatial resolution and 2.7Hz sampling of high-speed arbitrary point strain. Moreover, we conducted three application tests to evaluate the effectiveness of SHM using BOCDA system, such as the panel buckling test, the dynamic strain measurement test, and the demonstration flight test using the prototype BOCDA system. We verify the effectiveness of the BOCDA system for the aircraft SHM, and clarify the necessary development subject for the actual application.

Airplane structure health monitoring by the optical frequency modulation Brillouin distributed measuring method

The necessity for Airplane structural health-monitoring technology has been increasing because of improvement of reliability and cost saving. Optical fiber sensor system is an attractive method for structural health monitoring, because of its lightweight, non-electromagnetic interference, and to be embeddable to composite structures. Especially the distributed optical fiber sensor fits the health monitoring for large-sized structures. However, the distributed optical fiber measurement system using the pulse light represented by BOTDR has low spatial resolution and long measurement interval. These performances have been the obstacle of application to airplane structure health monitoring system. Then, the authors have proposed the Brillouin optical frequency modulation method for improvement of the spatial resolution and shortening of measurement intervals. In this work, we conducted basic approach in order to develop Brillouin Optical Frequency Domain Analysis (BOFDA) measurement system, such as pump power property and frequency modulation property for Brillouin stimulated light. We confirmed ability to measure stimulated Brillouin Scattering light in 50mm section. Moreover, We considered the optical fiber sensor installation issue on the airplane structure. The issue is optical fiber sensor birefringence under asymmetric load and durability of installation method. We conducted two confirmatory tests for the issues. The proposed installation method has adequate performance. From these results, it was confirmed that BOFDA system has potential to be applied to an airplane structure health monitoring system.