Microwave Photonic Sensing Demodulation System Based On A Chirped Spectral Microfiber F-P Interferometer

Fiber optic sensors are widely used in engineering security,aerospace and medical testing applications.How to demodulate fiber optic sensors accurately is very important.Compared with the traditional wavelength demodulation technology,the microwave photonic demodulation technology has the advantages of fast demodulation speed,high precision and high resolution.Meanwhile,the combination of the fiber Fabry-Perot(F-P)interferometer as a representative fiber optic sensor and microwave photonics technology can greatly enhance the performance of the sensing demodulation system.In this paper,we discovered a new way to achieve the spectral chirped microfiber F-P interferometer and proposed a microwave photonics sensing demodulation system based on the microfiber F-P interferometer.We fabricated the spectral chirped microfiber F-P interferometer by etching one long Bragg fiber grating on a microfiber and study the formation mechanism of the spectral chirped interferometer.The microfiber F-P interferometer has a reflection spectral wavelength range of more than 30 nm with good chirp characteristics,and the modulation depth of F-P interferometer is 20 dB.For the microfiber F-P interferometer,we integrated it into the microwave photonics demodulation system.In this paper,we theoretically analyzed the principle of the microwave photonic demodulation system and set up the experimental light path.The spectral chirped microfiber F-P interferometer is used as a spectral shaping component in the system,and the frequency domain information is transformed into the time domain by using the frequency swept laser.The high-resolution sensing information sampling process is realized by the data acquisition card,and is used for sensing demodulation.The sensing results of the proposed system under different external environment changes,such as the strain,temperature and refractive index are also given.In this paper,the microwave photonic sensing demodulation system is applied to biomedical sensing to diagnose p53 protein.The microfiber F-P interferometer is used as a fiber optical probe and the surface molecular modification is achieved by the molecular layer self-assembly method.The sensing system has good specificity and repeatability and its detection limit against the p53 protein antigen is 10 pg/mL.