What material surrounds the center tube in fiber optics?

In fiber optics, the material that surrounds the center tube, which is made up of the core where light signals travel, is known as cladding. Cladding is typically composed of a dielectric material that has a lower refractive index than the core. This difference in refractive index is crucial because it helps to keep the light confined within the core through the process of total internal reflection.

The cladding performs several functions: it protects the core from external interference, minimizes signal loss, and provides structural support. Its proper functioning is essential for maintaining the integrity and efficiency of the fiber optic communication system.

While other materials like the buffer coating and outer jacket provide additional layers of protection and support to the fiber, they do not specifically surround the core in the same manner as cladding does. The buffer coating is usually applied around the cladding to protect against physical stress and moisture, while the outer jacket serves as the final layer that offers environmental protection. Hence, cladding is the correct answer as it directly correlates to the structure surrounding the core of the fiber.