Development of Fiber Bragg Grating Strain Amplification Sensor For Use In Nuclear Power Plants

This paper outlines the motivation for structural health monitoring with fiber Bragg grating (FBG) strain sensors in nuclear power plants where a high measurement resolution is normally required. Hence, a mechanical strain amplification is needed to increase the strain sensitivities. To ensure long-term stability, an epoxy-free mechanical strain amplification sensor is constructed using a Kovar encapsulated FBG. The strain response of the sensor is characterized using an extensometer. It was found that the achieved sensitivity of
$1.16\pm 0.008 \ \text{pm}/\mu\varepsilon$
yields a strain resolution of 0.43
$\pm 0.003 \ \mu\varepsilon$
with current interrogation method - which exceeds the required strain resolution for the postulated scenario. However, if a higher resolution is required, it can be achieved by using an interrogator with a higher wavelength resolution or using a strain amplification with a larger strain amplification coefficient.