[CCoE Notice] PhD Dissertation Presentation

[Abercrombie, Irene F]

PhD Dissertation Defense

Development of Advanced Fiber Bragg Grating Based Sensors

Siu Chun Michael Ho

Date: Monday, November 19th, 2012

Location: ME Large Conference Room
Time: 12:00 pm

Committee Chair: Dr. Gangbing Song

Committee Members:
Dr. Matthew Franchek
Dr. Li Sun
Dr. Yi-Lung Mo
Dr. Mehdi Razavi

The discovery of fiber optics opened the door to a vast new world of possibilities in sensing technology. One important class of fiber optic sensor is the fiber Bragg grating (FBG) structure. The compactness and low loss properties of the FBG make it a highly versatile sensor, and has allowed efficient deployment of FBGs in many different technological fields.

This dissertation describes five different projects for the innovative design and application of FBG-based sensors. In the first project, an FBG was used as a contact level sensor allowing surgeons to gauge their level of contact with the heart wall in order to avoid perforation during cardiac ablation procedures. The sensor was able to determine the onset of contact and was also able to observe a potential warning sign of impending perforation.

In the second project, an FBG-based sensor for the detection of liquid moisture was developed, for use in detecting harmful water ingress in civil structures. Through the use of super absorbent polymers (SAPs) and an innovative sensor design, the sensor was able to undergo multiple loading cycles (up to 1 mL was tested) as well as survive flooding conditions.

In the third project, two wavelength matched FBGs were used to create a set up allowing the measurement of high frequency vibrations. Measurement of acoustic vibrations generated by a piezoelectric wafer up to 100 KHz was demonstrated. A basic identification of a model wind turbine blade was performed using this set up.

In the fourth project, an FBG sensor network consisting of multiplexed strain, temperature, and water sensors (23 sensors total) was deployed for the monitoring of a grout cube that models the wall of a nuclear containment facility. Cracking, thermal fluctuations and water ingress were detected by the FBG sensor network over a period of about two months.

In the fifth project, FBG strain sensors were used to investigate the bond slip of reinforcing tendons of a prestressed concrete bridge girder. The sensors were able to track the entire bond slip process from a local perspective, which was up to now not yet accomplished using conventional sensors.

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