Wavelength–Phase Hybrid Coding Optical Fiber Medical Monitor With Intracranial Pressure and Temperature Dynamic Self-Decoupling

The simultaneous monitoring of intracranial pressure (ICP) and intracranial temperature (ICT) are essential processes for assessing neurocritical conditions and preventing secondary brain injury. This study develops a medical monitor employing the optical fiber sensing technique, with a wavelength-phase hybrid coding approach, to simultaneously measure pressure and temperature. The optical fiber sensor is configured with a Fabry-Pérot (F-P) cavity and a fiber Bragg grating (FBG). The F-P cavity is fabricated through precision cutting and polishing, showing the advantages of controllable performance and low cost. Aiming at the multi-feature spectrum demodulation, this work combined the discrete Fourier transform with a centroid peak-detection technique to propose a wavelength-phase calculation strategy. Experimentally measuring range of the designed monitor is -300~300mmHg with a sensitivity of 248.67pm/mmHg. The error of pressure was reduced to a lower level of 2.48% by using temperature compensation. Additionally, the study constructed ex vivo tissue and in vivo animal experiments designed to test the monitor's performance. The results show that the monitor can accurately measure ICP and brain temperature, and it exhibits rapid response characteristics compared to commercial monitors. Such merits show the great potential of the monitor in the diagnosis and surveillance of neurocritical care patients.