Optical Pdms Microfibre Sensor For Displacement Determination

Daniel Kacik,Norbert Tarjanyi,Ivan Martincek

doi:10.26552/com.c.2017.3.26-29

Abstract

We prepared and demonstrated the usage of an optical polydimethylsiloxane (PDMS) microfibre sensor for displacement measurement. The sensor consists of PDMS microfibre placed between two conventional single-mode optical fibres. For proper bend of the microfibre the structure forms Mach-Zehnder interferometer. In that case, one arm of the interferometer consists of the microfibre and second one of the air. In addition, it is possible to resize the air arm in a range of several tens of micrometres with sufficient ratio of intensities between lights transmitted through the interferometer arms. For optical paths difference smaller than optical coherence of light source one can observe the interference of light. Determination of the displacement was done based on the spectral shift of interference pattern for particular lengths of air arm. The sensitivity of the sensor was 2.5 nm/μm.

Highlights

Optical devices based on optical microfibres can be used in a wide range of applications for their unique properties such as large evanescent field and strong confinement of the propagated light [1]
PDMS microfibre was created by gradual distancing of single-mode fibres ends (Fig. 1c) together with in-situ controlling the axial position by signal level
This microfiber was formed on the PDMS spherical segments with height of about 50 micrometres placed at the end faces of SMFs

Summary

Introduction

Optical devices based on optical microfibres can be used in a wide range of applications for their unique properties such as large evanescent field and strong confinement of the propagated light [1]. The optical microfibres can be arranged in different configurations such as taper [2], knot resonator [3], part of interferometers [2, 4, 5] and made from different materials such as silica [6, 7], polysiloxanes [5] This diversity predisposes them to sensing various physical quantities, for example temperature [7, 8], strain [7, 8], refractive index [9], volatile organic compounds [1, 10], current [4] and displacement [2, 11]. Axial alignment of SMFs with PDMS joint was mechanically adjusted by 3D microstages

Optical microfibre fabrication

Mach-Zehnder interferometer

Displacement sensing

Conclusion