This lab manual describes a series of experiments using side illuminated optical fibers. It was in 1989, 26 years ago, when AT&T Bell Labs’ scientists described, for the first time, a side illuminated optical fiber sensor. Their original device had a fluorescent cladding sensitive to oxygen and became the only known configuration for the next 16 years. These scientists recognized, very early, that this technique provided a much higher signal to noise ratio, SNR, if compared to the regular way optical fibers were used: by axial illumination. However, despite this recognition, these pioneers abandoned their own unique concept and left the least travelled road. At the end, the task of championing this neglected technique befell upon this author who started his work at the same time these researchers published their first paper. For this reason, I can also be counted among its early pioneers.
Despite side illumination’s simplicity, low cost and high SNR, it did not get much attention in its first 12 years. However, it is now clear, although only in hindsight, that sensors based on side illumination could have been developed and commercially deployed in the early/mid 1990’s. For this reason, it is puzzling that very little attention was given to this technique: especially in view of the fact that, even today, axial illumination is plagued with low SNR, expensive instrumentation and low spatial resolution. So, while the scientific community kept on developing devices using axial illumination, photonics crystal fibers and Bragg gratings, side illumination languished, almost forgotten, between 1995 and 2003. Definitely, such state of affairs can only be explained in the context of Murphy’s Laws…
Until 2001, side illumination was a technique that was exploited only in the US. However, little by little, interest grew in Europe, Brazil, India, Canada, South Korea, China, Australia and Hong Kong. The numbers are finally starting to paint a better
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