What does normalized frequency determine in optical fibers?

Normalized frequency, often referred to as the V-number or V-parameter, is a critical factor in the analysis of optical fibers, particularly in determining how many propagation modes a fiber can support. It is calculated using the formula V = (2π/λ) * a * NA, where λ is the wavelength of light in a vacuum, a is the radius of the core of the fiber, and NA is the numerical aperture.

When the normalized frequency is below a certain value (typically around 2.405 for step-index fibers), the fiber will only support a single mode of light. As the normalized frequency increases, the capacity for the fiber to support multimodes also increases. Hence, this parameter is pivotal for understanding the modal behavior of the fiber and how effectively it can transmit signals without interference from multiple modes.

In contrast, the other options relate to different characteristics of optical fibers. Loss of signal power is primarily influenced by factors such as attenuation and scattering but is not determined by the normalized frequency directly. The index of refraction is a material property that affects light propagation but does not indicate the number of modes. Lastly, the type of cladding is essential for defining the light confinement in the core but is independent of the fiber’s normalized frequency.