Introduction

A new and low cost optical fibre sensing system for monitoring the diffusion of corrosive media (water, acids, etc.) and the degradation through the thickness of polymers and polymer composites.

Technical features

The sensor is made by depleting, in a section of few cm, the cladding of a commercial optical fibre for telecommunication. Because of the cladding removal, the fibre becomes sensitive to the surrounding environment. The sensor is defined as an Evanescent Wave Optical Sensor (EWOS), since it relies upon the light “leaking” from the fibre that interacts with the surrounding material. The fibre sensor is also equipped with a mirror deposited at the termination of the depleted section, so that it can be used as a probe by a proper connection to an optical source and a spectrometer. The diffusion of water or other corrosive chemicals is probed by recording the spectral attenuation of the fibre sensor that is, by monitoring how an optical signal changes while propagating through the sensor.

Possible Applications

• Applications where polymers and polymer composites are used in hostile environments: oil and gas industry, marine, aerospace and renewable energy systems;
• Support in the development of accelerated aging tests of polymer and composites;
• Disposable probes for chemicals.

Advantages

• It exhibits a 10-fold reduction in cost, compared to commercial optical fibre sensors based on Bragg gratings;
• Easy manufacturing, even in an industrial framework;
• The sensor can be tailored with sensitive coatings (e.g. fluorescent materials) to make it sensitive to particular chemicals.