Encapsulated quantum dot nanofilms inside hollow core optical fibers for temperature measurement

In this paper, a way to build a nanostructured coating on the inner surface of a hollow core fiber (HCF) is presented. This coated HCF is subsequently spliced to two standard multimode fibers (MMF) obtaining an encapsulated all fiber structure that protects the nanocoating from the environment. Using quantum dot (QD) nanofilms in this structure, an improvement in the photobleaching effect is observed with respect to previous fiber optic temperature sensors based on similar QD nanofilms. When the film is deposited on the outer surface of the fiber, the sensors suffered an 80% decrease in the fluorescence emission after 1.5 h of continuous illumination. The enhanced structure presented here achieves a diminution of only 6.3% after 4 h at the same conditions. In addition, it is experimentally shown that these sensors can be used in a parallel setup to measure temperature changes simultaneously in two different locations.