High sensitivity micro-fiber Mach-Zehnder interferometric temperature sensors with a high index ring layer.

Yuqi Wu,Hu Zhang,Liqiang Zhang,Xia Zhang,Lixia Xi,Dong Yan,Xiaoguang Zhang,B M A Rahman,Nan-Kuang Chen,Xuan Li,Zhen Tian,Kenneth T V Grattan

doi:10.1364/oe.27.034247

Abstract

The influence of the high index ring layer (HIRL) in a tapered fiber Mach-Zehnder interferometer (MZI) on the interference observed, and thus on its potential applications in temperature sensing, has been investigated. The MZI was comprised of a tapered Ring Core Fiber (RCF), spliced between two single mode fibers (SMF). Since part of core mode from the SMF was converted into cladding modes in the RCF, due to the mismatch in the cores between the RCF and SMF, the residual power enters and then propagates along the center of the RCF (silica). The difference in phase between the radiation travelling along these different paths is separated by the HIRL to generate an interference effect. Compared with fiber interferometers based on core and cladding mode interference, the thin fiber HIRL is capable of separating the high order cladding modes and the silica core mode, under grazing incident conditions. Therefore, the optical path difference (OPD) and the sensitivity are both substantially improved over what is seen in conventional devices, showing their potential for interferometric temperature sensor applications. The optimum temperature sensitivity obtained was 186.6 pm/°C, which is ∼ 11.7 times higher than has been reported previously.

Highlights

Fiber optic interferometers are important components for communications systems, lasers, imaging and for optical fiber-based sensing systems
Experimental results and discussion When used for measurement evaluations, radiation from a broadband SLD light source was launched into the Mach-Zehnder interferometer (MZI) and the interference patterns were recorded by use of an Optical Spectrum
The corresponding mode distribution is more like the situation seen in Fig. 4(d), where the mode patterns are not optical angular momentum (OAM) modes

Summary

Introduction

Fiber optic interferometers are important components for communications systems, lasers, imaging and for optical fiber-based sensing systems. By contrast, creating a HIRL in RCF is found to be a good method to efficiently increase the OPD per unit length by separating the core and high order cladding modes, to travel through different paths, as part of miniaturizing such fiber interferometers.

Results

Conclusion