Comparative Analyses of Bi-Tapered Fiber Mach–Zehnder Interferometer for Refractive Index Sensing

In this paper, a high sensitivity of splicing regions tapered photonic crystal fiber (PCF) Mach-Zehnder interferometric refractive index (RI) sensor is described and experimentally demonstrated. Compared with cascaded bi-tapered single-mode fiber (SMF) Mach-Zehnder interferometer (MZI), the splicing regions tapered PCF MZI have higher sensitivity for the reason that it can better control and excite higher order modes, and has lower energy loss than cascaded bi-tapered PCF in the process of light transmission. Experimental results indicate that the RI sensitivity of splicing regions tapered PCF MZI could be up to 240.16 nm/RIU which is almost four times of cascaded bi-tapered SMF in the RI range of 1.3333-1.3792. Meanwhile, this splicing region tapered PCF Mach-Zehnder interferometric RI sensor has the advantages of higher RI sensitivity, good linearity, simple in making, and more potential practical value in the measurement of external RI.