We all know that there are some limiting factors affests lifespan of fiber optic cable, Such as the long term stress on the fiber and the largest flaw on the fiber surface, etc.
After professionally designed and engineered structure design, Barring cable damage and water ingress, the design life of fiber cables was engineered to be approximately 20 to 25 years.
GYTA53 is a typical underground optical cable, single-mode/multimode fibers are positioned in the loose tubes, the tubes are filled with water blocking filling compound.Tubes and fillers are stranded around the strength member into a circular cable core. An Aluminum Polyethylene Laminate(APL) is applied around the core. Which is filled with the filling compound to protect it. Then the cable is completed with a thin PE sheath. After PSP is applied over the inner sheath, the cable is completed with a PE outer sheath.
As its special structure design,in practice the cable will last much longer than that under normal conditions.
1，The following measures are taken to ensure the water blocking performance of the cable.
2，Single steel wire used as the central strength Member.
3，Special water-blocking filling compound in the loose tube.
4，100% cable core filling,APL and PSP moisture barrier.
So it is hard to estimate the real lifespan of fiber optic cable, It depends on how it is used, installed, protected and the humidity. The biggest threat to the lifetime of fiber that we know is water. Water molecules will migrate into the class changing the refractive index.