Refractive index sensor with asymmetrical fiber Mach-Zehnder interferometer based on concatenating single-mode abrupt taper and core-offset section

摘要

A novel refractive index (RI) sensor based on an asymmetrical fiber Mach-Zehnder interferometer (AFMZI) was realized by concatenating single-mode abrupt taper and core-off section. Compared with the normal two-taper MZI, the proposed sensor enlarges the evanescent field in the surrounding medium through the core-offset section. As a result, the RI sensitivity to the surrounding medium can be improved. Experimental results show that the RI sensitivity of the proposed sensor is 28.2 nm/RIU (refractive index unit) and 59.2 nm/RIU for interferometer length of 30 mm and 50 mm, respectively. It is much higher than the RI sensitivity of the normal two-taper MZI which is 14.7 nm/RIU and 19.1 nm/RIU for the corresponding interferometer length. Such kinds of low cost and highly sensitive RI sensor would find application in chemical and biological sensing fields.