Certified Fiber Optics Practice Exam

The part of a multimode optical fiber acting as a mode filter is known as:

1. Coating

2. Core

3. Buffer

4. Cladding

The correct answer is: Cladding

In multimode optical fibers, the cladding plays a crucial role in acting as a mode filter. The cladding is a layer of material that surrounds the core, which is where light is transmitted. The primary function of the cladding is to maintain the total internal reflection of light within the core by having a lower refractive index. This refractive index difference between the core and cladding helps to confine the light to the core, allowing only specific modes to propagate through the fiber while filtering out higher-order modes that may result in signal loss or distortion. By restricting the number of modes that can be supported, the cladding effectively enhances the performance of the fiber, particularly over longer distances or in high-bandwidth applications. In contrast, the other components fulfill different roles: the coating protects the fiber from environmental damage, the buffer serves as a protective layer to add strength, and the core is the central part where light travels but does not filter modes. Therefore, the cladding's function as a mode filter is essential for maintaining the integrity of the signal transmitted through the multimode fiber.