**1. Introduction**

Optical fiber (OF) technology has many decades of research and development mainly focused in telecommunication applications. Other classical applications for optical fibers include sensors, endoscopic imaging, and illumination.

Decades ago, in the 1970s, scientists of American Telephone and Telegraph (AT&T) had the idea to use the fiber to supply energy using optical fiber to make a sound alert in telephones, instead of the electric option. The concept of power over fiber (PoF) [1] was born this way. In

other words, beyond their classical applications, optical fibers can also be used to transport optical energy to powering electric or electronic devices remotely. This is the concept of PoF.

Since that time in the 1970s, many applications have emerged for PoF mainly in two different areas: telecommunications and utilities.

Why PoF is interesting? The reasons depend on the applications but they are associated to the optical fiber characteristics.

For telecom applications, the key factors are (i) PoF eliminates the necessity of batteries, solar panels, and long cupper feeder wires in the remote sites, improving the reliability and the security of the system; (ii) PoF permits the reduction of the space and the installation cost in remote sites, which is very important to telecom companies.

For electrical utilities, there are at least four key factors: (i) PoF uses optical fiber, which is made of nonconductive material. This characteristic is important because in most applications in electrical world, the sensors are placed in high voltage. Any conductance in high‐voltage elements can create current leaks; (ii) optical fiber is immune to electromagnetic interferences. The electrical world environment is polluted of electromagnetic interferences; therefore, optical fiber can transmit signals without quality degradation; (iii) the optical fiber eliminates the need to run conductive copper wire into a high‐ground potential rise (GPR) zone. GPR arises when lightning strikes occur in substations and can cause severe interference problems in electronic equipment and systems. Considering that the sensor using PoF has a complete galvanic isolation to the ground potential, it is practically immune to the GPR effects; and (iv) there are many low‐cost/low‐power/high‐efficiency electronic sensors available for transmission lines and substations monitoring that can be supplied by PoF without incurring in the described problems.

This chapter describes a revision of PoF, its technical principles, main elements, technologies, and the applications in telecom and in utilities, developed by the author's group.
