How do signal losses due to microbend-induced attenuation in optical fiber behave as mode-field diameter increases?

As the mode-field diameter of optical fiber increases, the phenomenon of microbend-induced attenuation tends to consistently decrease. This behavior can be attributed to the way light interacts with the fiber.

Microbends in optical fiber arise from imperfections or pressure points along the length of the fiber that can cause variations in the fiber's curvature. When the mode-field diameter is larger, the optical mode is distributed over a larger area within the fiber's core. This reduction in the intensity of the light at the core-cladding boundary means that the impact of microbends on signal loss is less pronounced. Essentially, with a larger mode field, the light is less susceptible to the localized distortions caused by these microbends, leading to lower attenuation levels.

In contrast, smaller mode-field diameters concentrate more light closer to the fiber boundary where bends and imperfections have a greater influence on signal integrity, resulting in higher levels of attenuation. Therefore, as the mode-field diameter increases, the attenuation caused by microbends decreases consistently.