UPNA campus iberus – Academica – e
2014
OPTICAL FIBER SENSORS BASED ON NANOSTRUCTURED MATERIALS FOR ENVIRONMENTAL APPLICATIONS
ADOLFO JOSUÉ RODRÍGUEZ RODRÍGUEZ

Abstract

Environmental pollution is the presence of physical, chemical or
biological agents in water, soil and air which are harmful to our health, safety and welfare of the people as well as plant and animal life. Economic activities are essential to the development of society; however, many of these activities are a constant source of
contamination. For example, leakage of fluids and gases in industrial plants adversely affect the health and hygiene for food processing, beverages, additives and raw materials causing serious environmental and economic impact on the general industry. The continual search for methods for developing measurement systems is a feature in the technological evolution of humankind. Optical fibers exhibit several advantages such as being immune to electromagnetic interferences, reduced dimensions, lightweight, low losses, easy multiplexation and resistant to corrosion for the development of optical fibers sensors.

However, we selected three applications were the principle of operation of our sensor provides an advantage over other reported sensors: gaseous ammonia detection for low concentrations, adulteration of alcoholic beverages detection and combustibles quality control. The overall objective of this research is to design, fabricate, deploy and verify the correct operation of optical fiber structures for the identification of interesting liquid and gaseous environmental pollutants.

The sensors parameters such as its sensitivity, reversibility,  reproducibility and accuracy of measurement for each type of sensor are also characterized. These results obtained from this thesis would be a useful work in the study of new materials applicable to optical sensors, while opening new avenues of research in the field of optical fiber sensors for industrial applications.

Sensor head fabrication

The sensor was fabricated using FT-200-EMT from Thorlabs Inc. (Newton, NJ, USA), which is a multimode fiber (MMF) with core and cladding diameters of 200 and 225 µm respectively. The advantage of this MMF is that the cladding is made of polymer which facilitates its removal in a specific section of the MMF. The sensor head (Fig. 1) is fabricated by removing the outer protective plastic jacket of the fiber. First, the MMF was cleaved and the end facet is silver coated using a
sputtering system (K675XD Quorum Technologies Ltd.), (Sacramento, CA, USA).

After this, a segment of 1.5 cm of the MMF cladding was carefully removed and cleaned with acetone to remove any remaining polymer waste. This section is located 2 cm away from the tip of the MMF. Finally, the un-cladded region was coated with the pH sensitive solution using a standard dip-coating technique and fully automated deposition system from Nadetech, Inc ®
(Pamplona, Spain).

 

Subjects: Optical fiber sensors; Nanoestructured materials