Numerical Aperture Calculator

The Numerical Aperture (NA) calculator computes the light-gathering ability of an optical fiber, based on the refractive indices of its core and cladding. Numerical aperture is a key factor that influences the fiber’s performance, affecting how well it can transmit light.

Core Index \( n_{\text{core}} \): The refractive index of the fiber core, which must be greater than the cladding index for the fiber to guide light effectively.

Cladding Index \( n_{\text{clad}} \): The refractive index of the fiber cladding, which is lower than the core index to create total internal reflection.

The Numerical Aperture is calculated using the following formula:

$$ NA = \sqrt{n_{\text{core}}^2 - n_{\text{clad}}^2} $$

Where:

• NA is the Numerical Aperture of the fiber.
• \( n_{\text{core}} \) is the refractive index of the core.
• \( n_{\text{clad}} \) is the refractive index of the cladding.

For light to be guided within the fiber, the core index must be greater than the cladding index. This calculator will warn you if the core index is less than or equal to the cladding index, as this configuration would not support efficient light transmission.

Once the valid values are entered, the calculator computes the numerical aperture, giving insight into the fiber’s acceptance angle—the range of angles at which light can enter the fiber and still be guided.