What are the primary causes of intrinsic loss in single-mode fiber?

The primary causes of intrinsic loss in single-mode fiber relate to the inherent properties of the fiber material and its structure. Material absorption, which occurs due to the inherent absorption of light by the fiber material, is a significant factor. Certain wavelengths can be absorbed more than others, depending on the composition of the fiber, leading to energy loss as the light travels through the medium.

Rayleigh scattering is another crucial contributor to intrinsic loss. It results from microscopic variations in the density and composition of the fiber, which cause scattering of light as it travels through the fiber. This scattering is dependent on the wavelength of the light and is a fundamental physical effect observed in all optical fibers.

These two phenomena—material absorption and Rayleigh scattering—are inherent to the fiber itself and are not due to any external factors, which differentiates them as primary causes of intrinsic loss, unlike splice loss, connector loss, or other external factors that are not intrinsic to the fiber's material properties.