Distributed Static and Dynamic Strain Measurements in Polymer Optical Fibers by Rayleigh Scattering.

Agnese Coscetta,Nunzio Cennamo,Lucia Bilro,Luigi Zeni,Ester Catalano,Ricardo Oliveira,Aldo Minardo,Enis Cerri

doi:10.3390/s21155049

Abstract

We demonstrate the use of a graded-index perfluorinated optical fiber (GI-POF) for distributed static and dynamic strain measurements based on Rayleigh scattering. The system is based on an amplitude-based phase-sensitive Optical Time-Domain Reflectometry (ϕ-OTDR) configuration, operated at the unconventional wavelength of 850 nm. Static strain measurements have been carried out at a spatial resolution of 4 m and for a strain up to 3.5% by exploiting the increase of the backscatter Rayleigh coefficient consequent to the application of a tensile strain, while vibration/acoustic measurements have been demonstrated for a sampling frequency up to 833 Hz by exploiting the vibration-induced changes in the backscatter Rayleigh intensity time-domain traces arising from coherent interference within the pulse. The reported tests demonstrate that polymer optical fibers can be used for cost-effective multiparameter sensing.

Highlights

Distributed optical fiber sensors based on Rayleigh scattering exploit the refractive index inhomogeneities that naturally occur along the fiber and can operate either in the time domain [1,2,3] or frequency domain [4,5]
We have shown that polymer optical fibers can be used for distributed static and dynamic strain measurements using a φ-OTDR setup operating at 850 nm
The static strain was detected by incoherent OTDR measurements at a spatial resolution of 4 m, using a wavelength-scanning method

Summary

Introduction

When applying the OTDR on a polymer optical fiber, a largely strained section can be identified through the induced reduction of the core diameter and the consequent increase of the backscatter intensity in that section [6]. The measurements have been carried out using a φ-OTDR setup based on heterodyne coherent detection and operating at the wavelength of 850 nm (see Figure 1).

Results

Conclusion