Enhanced Mach-Zehnder interferometer multimode-single-mode-multimode fiber optic refractive index sensor based on surface plasmon resonance

In this paper, an all-fiber Mach-Zehnder interferometer (MZI) sensor for refractive index (RI) measuring is presented, which is based on Multimode-Single-mode-Multimode (MSM) fiber. The effects of both reducing the radius of the sensing part and the surface plasmon resonance (SPR) on its efficiency are investigated. Increasing the interaction of high-order modes with external media, caused by etching the cladding layer of the single-mode fiber part, significantly improves the sensitivity. Both wavelength and intensity interrogation approaches are employed to study the Multimode-etched Single-mode-Multimode (MESM) fiber sensor. The intensity and the wavelength sensitivities for the RI measurement in the range of 1.428-1.458 are obtained as-2306.754 %/RIU and 1315.74 nm/RIU, respectively. Finally, the MESM-SPR sensor is proposed and characterized. Results exhibit high performance in the RI range of 1.333 to 1.357, in which the sensitivity of 1437.056 nm/RIU is achieved. The advantages like low cost, high sensitivity, and simple fabrication methods make these sensors promising devices for chemical, food industry, and biosensing applications.

Automated summary

This paper presents an all-fiber Mach-Zehnder interferometer (MZI) sensor for refractive index (RI) measurement using Multimode-Single-mode-Multimode (MSM) fiber. The effects of reducing the radius of the sensing part and surface plasmon resonance (SPR) on efficiency are investigated. The sensitivity is significantly improved by increasing the interaction between high-order modes and external media through etching the cladding layer of the single-mode fiber part. Both wavelength and intensity interrogation methods are used to study the Multimode-etched Single-mode-Multimode (MESM) fiber sensor.