A power over fiber system includes: a first data communication device including a power sourcing equipment device; a second data communication device including a photoelectric-conversion-and-optical-communication unit including a powered device; and an optical fiber cable. The first data communication device is capable of controlling low power supply and high power supply of the power sourcing equipment device. Feed electric power by the high power supply exceeds that by the low power supply. The first data communication device enables the high power supply after starting the low power supply to the second data communication device and receiving, therefrom, a signal indicating that the photoelectric-conversion-and-optical-communication unit has started. The photoelectric-conversion-and-optical-communication unit starts and transmits the signal to the first data communication device when receiving the low power supply, and enables extension of a range of a target that receives electric power from the powered device when receiving the high power supply.