What does the gel, tape, or powder in a loose tube/buffered fiber optic cable primarily protect the optical fiber from?

The gel, tape, or powder in a loose tube or buffered fiber optic cable is designed primarily to protect the optical fiber from water. This protective element serves as a moisture barrier, preventing water ingress that can lead to fiber damage or signal degradation. Water exposure can have detrimental effects on the performance of fiber optics, as moisture can cause attenuation or even total failure of the optical signal.

In addition to water protection, the gel and other materials may provide some level of mechanical protection and stability to the fibers within the cable, but the primary function is to safeguard against moisture. This is particularly important for cables installed in underground or outdoor environments where exposure to water is a significant risk.