Development of a low-cost 3 × 3 coupler Mach–Zehnder interferometric optical fibre vibration sensor

Abstract

In this paper, a low-cost 3 × 3 coupler Mach–Zehnder interferometric optical fibre vibration sensor is proposed. Unlike the traditional Mach–Zehnder interferometer with a strain free reference arm, two parallel optical fibres with different strain transfer sensitivities are adopted. With the proper demodulation algorithm, the time rate of change in strain can be computed from the light signal of the outputs of a 3 × 3 coupler. The proposed optical fibre vibration sensor is verified by experiment. The vibrating frequency spectrum of a two-layer metal frame is measured by both the proposed optical fibre vibration sensor and micro-electro-mechanical system (MEMS)-based accelerometers. It was found that the proposed vibration sensor is more sensitive compared to the MEMS-based accelerometer, unless it is located near a zero-strain region. Several proposed sensors can easily be multiplexed to minimise the overall cost.

Keywords:

• optical fibre
• Mach-Zehnder interferometer
• vibration sensor

Acknowledgements

The work described in this paper was fully supported by Ir Prof Christopher K Y Leung of the Department of Civil and Environmental Engineering of the Hong Kong University of Science and Technology in Hong Kong.

ORCID

K T Wan http://orcid.org/0000-0002-5418-5501

Additional information

Notes on contributors

Kai Tai Wan

Notes on contributors

Ir Dr Kai Tai Wan is a Lecturer in Civil Engineering specialising in building and construction materials as well as advanced sensor technologies and structural health monitoring. He is a registered Material Engineer. Before joining the Brunel University, he worked in the Construction and Building Materials Department of the Research and Development Division at the Nano and Advanced Materials Institute (NAMI) in Hong Kong. He was the principle investigator of more than HK$10M research projects and the leader of a multidisciplinary research team to develop various kinds of advanced construction and building materials, such as lightweight to ultra-lightweight low-shrinkage high-strength water-repelling foamed concrete, pseudo ductile cementitious composite with discrete recycled polymer fibre, super-hydrophobic coating for concrete, 2-in-1 hydrophobic waterproofing and pore-liner polymeric paint for concrete and fabric-reinforced cementitious matrix with high-performance manmade as well as natural fibre. Ir Dr Wan has developed various kinds of advanced sensors for structural health monitoring such as distributed optical fibre crack sensors, optical fibre corrosion sensors, tuneable polymer optical fibre integral strain sensors, Mach–Zehnder interferometric vibration sensors, distributed wind pressure sensors and two-dimensional crack sensors. The first two sensors were developed from laboratory prototypes to field trials.