Why to use Fiber Cables    
Fiber being glass it is immune to EMI and RFI also. No Lightning problems.Electrical cables need grounding and also shields to protect data. Whereas Fiber does not need shields or Ground connections. Saves time and money.  Fiber being glass if cut cannot start a fire. No sparks. However cable can burn as cables have plastic Jackets. Fiber Cables are physically very small so less weight and space required. However they are very strong as cables use Kevlar strength member (stronger than steel)

 Fiber cables can carry lot more data compared to copper cables. (Large Bandwidth). E.g. we can replace 300 pair copper telephone cable with 0.25 inch Fiber cable. Copper cables are limited to few meters , even Coax(good Quality) is limited in distance, 200 to 300 Meters .Computer cables are limited to few meters e.g. USB is limited to 5 meters .Whereas Fiber cables can go up to 100km. Telecom Fiber cables go even longer.