Development of a Combined Fabry-Perot and Fiber Bragg Grating Sensor for Accurate Temperature and Concentration Detection in Biological Applications

Accurate monitoring of temperature and concentration changes in biological samples is crucial for biomedical diagnostics and environmental monitoring. The development and mathematical modeling of a novel combined fiber-optic sensor integrating a Fabry-Perot interferometer (FPI) and a fiber Bragg grating (FBG) within a single-mode optical fiber are presented in this paper. This integration enables simultaneous and precise measurements of temperature and refractive index changes in biological applications. The sensor's performance was modeled using transfer matrix methods and reflection/transmission coefficients to simulate spectral responses under varying conditions, including external refractive index, cavity length, grating period, induced refractive index change, and temperature effects. Results demonstrate that the combined sensor exhibits high sensitivity to temperature changes, with a temperature sensitivity of approximately 15–16 pm/°C, significantly surpassing traditional quartz-based sensors. It effectively detects minute variations in the refractive index of the external medium, such as changes in blood composition, allowing for distinction between healthy and diseased states. The enhanced capabilities of the combined FPI-FBG structure provide selective and improved detection compared to conventional sensors. The sensor can be interrogated using both spectral analysis and radio-photonic methods, contributing to increased precision and reliability in biomedical diagnostics, biochemical analysis, and environmental monitoring.