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

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. (C) 2012 Elsevier Ltd. All rights reserved.