LC-FBG-Based Microwave Photonic System for Refractometric Biosensors

A structure of a refractometric fiber-optic biosensor with microwave photonics processing of information about refractive index of the medium surrounding the sensor is proposed. The sensor is made on a linearly chirped fiber Bragg grating and contains two phase $\pi$-shifts spaced along the length of the grating in its structure: one fixed in magnitude and location, the second, changing its parameters, in the fiber section with an etched cladding. Upon contact of the measured medium with a portion of the fiber containing the second phase shift, there is a change in its magnitude and frequency position, depending on the refractive index. The possibility of detecting changes in the refractive index with a resolving power of $1.5\times 10^{-6}$ RIU is shown.