Fiber optic networks provide highly reliable and intrinsically safe communications systems for underground mines. Comprised of small strands of glass, optical fiber cables can transmit light at very high speeds. Since these cables do not contain electrical conductors, they are intrinsically safe for use in underground hazardous locations. By eliminating spark hazards, the risk of ignition from flammable gasses is minimized. Furthermore, since optical fibers are composed of glass, they are immune to induced currents, cross talk and EMI generated by large AC motors and other electrical equipment used in mining operations.
Fiber optic cables and connectors are designed and qualified for use in mines by validating the mechanical strength required to install and operate the cable in an underground environment. Pull strength, crush resistance, impact strength and flexibility are key characteristics of qualified cables. Resistance to flame spread, per local code requirements such as MSHA, are additional requirements. In this article, we will review the basics of optical fiber, cable and connection systems for use in underground mines and show how these elements are specified and deployed in an underground installation.