Fiber Bragg Gratings for Temperature Measurements Under Thermal Gradients: Comparison Between Two Different Lengths

In recent decades, fiber Bragg grating (FBG) sensors found widespread acceptance in several biomedical applications thanks to their indisputable advantages. Thermal ablation treatments (TATs) account for one of the fields where FBGs have gained large applicability for temperature measurements. The sensing element length can affect the accuracy of the FBG measurement in this application. A longer length provides a more prominent peak in the FBG reflected spectrum, resulting in a higher signal-to-noise ratio (SNR). A shorter FBG length implies a lower SNR but offers the benefits of better spatial resolution. Therefore, the choice of an adequate length can be crucial to minimize measurement errors, but the literature lacks exhaustive investigations on this parameter. The aim of our study is to supply additional knowledge about the effect of two different FBG lengths on temperature estimation in the presence of linear thermal gradients and with gradients mimicking the condition caused by TATs. In both cases, we compared the output of a 10-mm FBG with those of four FBGs 1 mm long, using a thermal camera as a reference instrument. Results suggest the better suitability of shorter sensors to retrieve thermal gradient information along their position instead of the longer FBG, which could lead to unacceptable measurement errors during TATs.

Automated summary

In recent decades, fiber Bragg grating (FBG) sensors have been widely used in biomedical applications, particularly in thermal ablation treatments. The choice of FBG length is crucial in minimizing measurement errors, yet there is a lack of comprehensive investigations on this parameter. Our study aims to provide additional knowledge on the effect of two different FBG lengths on temperature estimation in the presence of thermal gradients. Results suggest that shorter FBG sensors are more suitable for retrieving thermal gradient information, while longer FBGs may lead to unacceptable measurement errors during thermal ablation treatments.