▎ 摘　　要

We report a simple, compact, and robust photonic crystal fiber (PCF)-based Mach-Zehnder modal interferometer coated with graphene oxide (GO) for monitoring refractive index (RI) of analyte (sucrose). GO is prepared by Hummers method, and the fabrication of sensing probe is achieved by splicing single-mode fiber with solid core PCF followed by collapsing of air holes at the end face of PCF. The PCF along with the collapsed region is functionalized and then coated with GO. The proposed tip sensor in reflection mode can be used for the detection of RI of a small quantity of sucrose in either intensity or/ and wavelength interrogation. Our experimental results show that the sensor has wavelength sensitivity as high as 230-nm/RIU along with very high intensity sensitivity of 130 dB/RIU with negligible shift in interference pattern with rise temperature.