The optical fiber is an important part of the flame detection system, if it lose efficacy then entire system will be fail. So the stability and reliability of optical fiber is very important.

The stable and reliable optical fiber needs reliable cooling air, but the cooling air only solves isolation between 350℃ secondary air and the optical fiber, flame radiation cannot be isolated. when carrier have been inappropriate and optical fiber have absorbed the radiation, fiber temperature will be very high and fiber have to bear more than 400 ℃temperature, so a general fiber already cannot endure and could not work (fiber into or out), this is why optical fiber are frequently damaged in some plants.

Therefore, the flame detection system is stable and reliable, the optical fiber must be able to endure at more than 450℃ temperature.