In a typical cross-section of single-mode fiber, which number represents the cladding?

In the typical cross-section of single-mode fiber, the cladding is represented by the layer that surrounds the core. The core is the central part of the fiber where light is transmitted, and the cladding provides a lower refractive index than the core, enabling total internal reflection of the light within the core.

The cladding serves several critical functions, including protecting the core and allowing light to remain contained within the core. In diagrams showing the cross-section of optical fibers, the cladding is typically illustrated as a distinct, often larger layer surrounding the core. Given these characteristics, option B, which represents the cladding, fits this description perfectly.

In contrast, the other options typically correspond to different components of the fiber structure. For example, the core might be a smaller inner circle, while additional layers, such as coatings or buffer sheaths, could be represented by other numbers in the diagram. Understanding the structure of fiber optics, especially single-mode fibers, is essential for grasping how they function and are utilized in telecommunications and networking.