Up-down Taper Based In-Fiber Mach-Zehnder Interferometer for Liquid Refractive Index Sensing

Xiaopeng Han; Chunyu Liu; Shengxu Jiang; Shuo Leng; Jiuru Yang

doi:10.3390/s19245440

Up-down Taper Based In-Fiber Mach-Zehnder Interferometer for Liquid Refractive Index Sensing

Sensors (Basel). 2019 Dec 10;19(24):5440. doi: 10.3390/s19245440.

Authors

Xiaopeng Han¹, Chunyu Liu^{1

2}, Shengxu Jiang¹, Shuo Leng¹, Jiuru Yang²

Affiliations

¹ College of Electronics Engineering, Heilongjiang University, Harbin 150080, China.
² Key Lab of Electronics Engineering, College of Heilongjiang Province, Heilongjiang University, Harbin 150080, China.

Abstract

A novel in-fiber Mach-Zehnder interferometer based on cascaded up-down-taper (UDT) structure is proposed by sandwiching a piece of polarization maintaining fiber between two single-mode fibers (SMF) and by utilizing over-fusion splicing method. The dual up tapers respectively act as fiber splitter/combiner, the down taper acts as an optical attenuator. The structure parameters are analyzed and optimized. A larger interference fringe extinction ratio ~15 dB is obtained to achieve refractive index (RI) sensing based on intensity demodulation. The experimental results show that the RI sensitivity is -310.40 dB/RIU with the linearity is improved to 0.99 in the range of 1.3164-1.3444. The corresponding resolution can reach 3.22 × 10^-5 RIU, which is 6.8 times higher than wavelength demodulation. The cross sensitivity which caused by temperature fluctuation is less than 1.4 × 10^-4.

Keywords: Mach-Zehnder interferometer; intensity demodulation; refractive index; up-down taper.