Plastic Optical Fibre Sensors for Structural Health Monitoring: A Review of Recent Progress

K S C Kuang,S T Quek,C G Koh,W J Cantwell,P J Scully

doi:10.1155/2009/312053

Abstract

While a number of literature reviews have been published in recent times on the applications of optical fibre sensors in smart structures research, these have mainly focused on the use of conventional glass‐based fibres. The availability of inexpensive, rugged, and large‐core plastic‐based optical fibres has resulted in growing interest amongst researchers in their use as low‐cost sensors in a variety of areas including chemical sensing, biomedicine, and the measurement of a range of physical parameters. The sensing principles used in plastic optical fibres are often similar to those developed in glass‐based fibres, but the advantages associated with plastic fibres render them attractive as an alternative to conventional glass fibres, and their ability to detect and measure physical parameters such as strain, stress, load, temperature, displacement, and pressure makes them suitable for structural health monitoring (SHM) applications. Increasingly their applications as sensors in the field of structural engineering are being studied and reported in literature. This article will provide a concise review of the applications of plastic optical fibre sensors for monitoring the integrity of engineering structures in the context of SHM.

Highlights

In recent years, structural health monitoring has attracted significant interest from academia, government agencies, and industries involved in a diverse field of disciplines including civil, marine, mechanical, military, aerospace, power generation, offshore and oil and gas
The results showed that the Optical time-domain reflectrometry (OTDR) backscatter signal increased in respond to widening crack width highlighting the feasibility of using Plastic optical fibres (POFs) OTDR sensor to detect cracks in masonry ad concrete structures
Long period grating mechanically imprinted onto microstructured POF; linear response limited to 2% strain; creeping observed beyond 3%; viscoelastic effects noted above 2% but minimal below 2%; significant material relaxation under constant strain

Summary

Introduction

Structural health monitoring has attracted significant interest from academia, government agencies, and industries involved in a diverse field of disciplines including civil, marine, mechanical, military, aerospace, power generation, offshore and oil and gas. Plastic optical fibres (POFs) with their large core sizes (diameters ranging typically from 0.25 mm to 1 mm are readily available) and high numerical apertures (0.47) lend themselves well to be used as intensity-based optical fibres sensors. Bragg gratings, which are commonly applied to single-mode silica fibres using ultra violet laser light to create the interference pattern to induce periodic changes in refractive index of the core, have been demonstrated on doped plastic optical fibres and undoped bulk PMMA in recent years [17,18,19]. It has been reported that plastic optical fibre has an elastic limit of 10% compared to 1% in silica and can withstand strains more than 30% without breakage [25]—this could be a significant benefit for structural health monitoring applications involving large strains greater than that measurable by glass-based fibre sensors. In view of the advantages associated with plastic optical fibres, intensive research is underway to assess their potential for smart structure and structural health monitoring applications

Recent Development in POF Sensors for SHM

Findings

Summary and Conclusions