To provide a prevention system of the breakage of a light source and an optical amplifier that can prevent the breakage of a transmission device with the light source, by providing a function detecting light and temperature generated by the self-progressing phenomena of the internal breaking of an optical fiber.

The prevention system 100 of the breakage of the light source is provided with an optical sensor close to the optical fiber of a transmission path 122 connected to the transmission device 121 with the light source, and a detector 101 for the self-progressing phenomena of the internal breaking of the optical fiber. The detector 101 for the self-progressing phenomena of the internal breaking of the optical fiber detects the light and temperature generated by the self-progressing phenomena of the internal breaking of the optical fiber on the way of the transmission path 122, and then sends various kinds of information indicating the state of the detected self-progressing phenomena of the internal breaking of the optical fiber to the transmission device 121. The transmission device 121 adjusts the output quantity of the light source based on the received various kinds of information indicating the state of the self-progressing phenomena of the internal breaking of the optical fiber.