Fiber optic cable carries data as pulses of light along glass or plastic strands. It is immune to electrical interference and covers far longer distances than copper, which makes it the usual answer for connecting buildings or reaching a camera several hundred meters from the switch. Each end needs a converter or a switch with fiber ports.
Copper runs out at 100 meters. Fiber is what a site uses when the distance is longer, the electrical environment is hostile, or two buildings need to be joined.
Fiber in a camera network
A camera far from the network closet can be served by a media converter or a switch with fiber ports, with copper for the last few meters. Fiber also links buildings without creating a conductive path between them. It carries no power, so the far end still needs a local supply.
Single-mode and multimode
Multimode fiber covers shorter distances inside and between nearby buildings, and single-mode covers much longer spans. Connectors and transceivers have to match the fiber type and the distance. Clean connectors matter, because dirt is a common cause of a link that works intermittently.