**Christian Cuadrado-Laborde**

**1**

**Figure 1.**

*General block diagram for an optical fiber sensor.*

**Chapter 1**

**1. Introduction**

orders of magnitudes higher.

Introductory Chapter: Application

The history of the use of optical fiber for sensing applications began with two different, but interrelated, discoveries: laser light and optical fibers. The first laser was built in 1960 by T. H. Maiman at Hughes Research Laboratories, based on the theoretical work by C. H. Townes and A. L. Schawlow. A laser provides a source of an intense coherent light, highly collimated, and quasi-monochromatic; its potential for data transfer was immediately envisaged. Naturally, first experiments involved the transmission of the laser beam through the air. However, a communication channel cannot be practically sustained propagating freely through the air, owing to atmospheric attenuation and weather influence. Researchers also conducted experiments by transmitting the laser beam through glass fibers, which soon became the preferred medium for transmission of light. First, optical fibers were not practical to sustain a communication channel mainly due to the presence of impurities in the fiber material, resulting in very high transmission losses (>1000 dB/km), until Corning presented at the beginning of the 1970s optical fibers with (in comparison) very lower transmission losses, with only a few dB/km. Today, typical transmission losses are below 0.2 dB/km. This represents an extraordinary improvement as compared with electrical signal transmission through coaxial cables, not to mention the wider bandwidth available, which is several

These developments paved the way to a plethora of different works on fiber optic sensing. But, what is an optical fiber sensor? **Figure 1** shows a block diagram of a typical optical fiber sensor. It is composed of a light source (which not only can be a laser, but also a broad band light source like a light emitting diode, etc.), the optical fiber itself transmits the light from the light source to the sensing area

of Optical Fiber for Sensing

*Christian Cuadrado-Laborde*

Instituto de Física Rosario (CONICET-UNR), Pontificia Universidad Católica Argentina, Facultad de Química e Ingeniería, Rosario, Argentina
