The typical structure of an optical fiber is a multi-layer coaxial cylinder, which is mainly composed of a core, a cladding, and a coating.

core

Located in the center of the fiber, the composition is high-purity silica, doped with a very small amount of dopant. The refractive index of the core is slightly higher than that of the cladding, the loss is lower than that of the cladding, and the light energy is mainly transmitted in the core.

layers

Located around the core, it is also composed of high-purity silica containing very small amounts of dopants. The cladding provides a reflective surface and optical isolation for the transmission of light, and plays a certain role in mechanical protection.

coating

The outermost layer of the fiber, consisting of acrylic, silicone rubber, and nylon. The coating protects the fiber from water vapor and mechanical abrasion.