A power over fiber system includes a power sourcing equipment, a powered device, an optical fiber cable, a power storage and a controller. The power sourcing equipment includes a semiconductor laser that oscillates with electric power, thereby outputting feed light. The powered device includes a photoelectric conversion element that converts the feed light into electric power. The optical fiber cable transmits the feed light from the power sourcing equipment to the powered device. The power storage stores the electric power. The controller performs a process of lowering an output level of the feed light in response to a value related to an electric power amount of the electric power stored in the power storage being equal to or higher than a predetermined threshold value, and performs a process of raising the output level in response to the value being lower than the predetermined threshold value.