Micro-Bubble F-P Cavity and FBG Cascade Structure-Based Pressure Sensor With Temperature Self-Compensation for Minimally Invasive Surgery

This paper presents a high-sensitivity optical fiber pressure sensor with temperature self-compensation for pressure measurement in minimally invasive surgery through a cascade structure of Fabry-Perot (F-P) interferometer and fiber Bragg grating (FBG). A micro-bubble is configured at the tip of the fiber to form an F-P cavity that is sensitive to pressure. A loose optical fiber inscribed with an FBG element is cascaded with the F-P cavity leading to temperature compensation for the designed sensor. The sensing theoretical model has been derived and combined with the finite element method (FEM) simulation the sensor structure has been determined as well. Fabrication processing of the designed sensor has been optimized and explored by experiments. Calibration experiment results indicate that the pressure sensitivity of the designed sensor is 8.93 pm/kPa, which is consistent with the simulated value. The temperature coupled error is less than 3.89% leading to a capability for temperature self-compensation. Several heart-vascular simulation experiments have been carried out to investigate the dynamic performance of the designed sensor, which shows the measured pressure errors within this confidence interval of [-2.56%, 2.54%] correspond to high confidence of 0.95. An in-vivo intracranial pressure (ICP) measurement experiment on the rat brain has been conducted to further validate the feasibility and effectiveness of the designed sensor.