What is considered the more accurate and technically correct measurement of the optical transport region of single-mode fiber?

The mode field diameter (MFD) is considered the more accurate and technically correct measurement of the optical transport region of single-mode fiber because it represents the effective area through which the light propagates. The MFD is critical in understanding how light behaves in the fiber and is influenced by the refractive index profile of the fiber's core, impacting various performance characteristics such as transmission loss and system capacity.

In single-mode fibers, the MFD is typically larger than the actual core diameter. This difference is important because it gives a better understanding of how the light field distributes in the fiber and the effective area available for carrying light signals. The MFD's value is also essential when calculating nonlinear effects and the power handling capability of the fiber.

In contrast, while core diameter and cladding diameter provide some information about the fiber's structure, they do not give a clear representation of the optical performance and light propagation characteristics as the MFD does. The effective area of the fiber is closely related to MFD but focuses more on the fiber's ability to handle power and is a broader measurement compared to MFD, which is more specific. Thus, mode field diameter captures the necessary attributes relevant to optical transport performance, making it the most accurate measurement in this context.