Characterization of fiber optic distributed temperature sensors for tissue laser ablation

Abstract

Abstract-Fiber optics is the most promising technology for distributed temperature sensing. The paper investigates the characterization of probes based on single or multiplexed fiber Bragg gratings, specifically conceived to evaluate the temperature distribution in applications that imply large temperature gradients, such as in laser induced thermal treatments of solid tumors. A setup for the characterization of fiber Bragg grating sensors in non uniform temperature conditions is described and examples of applications in case that mimic actual working conditions are reported.

Linearly chirped fiber Bragg grating response to thermal gradient: from bench tests to the real-time assessment during in vivo laser ablations of biological tissue

“…24 Additionally, FBGs allow for the simultaneous measurement of temperature in different positions along only one fiber. 6,11 LCFBGs provide an essential additional feature for this specific application, namely, the possibility to measure thermal gradients in real time. The correlation between the experienced thermal gradient and spectrum change is a demanding task, which requires a preliminary analysis.…”

“…Equation 5 shows a linear relationship between each portion of the grating and the variation of the corresponding local temperature. 11,22 3 Static Calibration of the Linearly Chirped Fiber Bragg Grating Sensor: Experimental Setup and Results…”

“…Uniform FBGs provide one temperature value, which is mostly related to the temperature averaged on the sensitive length of the grating. As a result, when there is a high thermal gradient, the length of the FBGs can influence the accuracy of the measurement, 10,11 and ideally punctual gratings can provide the real value of the tissue temperature in a specific place. To have the tissue temperature distributed around the applicator may be particularly beneficial in providing direct insights into the thermal gradient.…”