What does the NA (Numerical Aperture) indicate in fiber optics?

The Numerical Aperture (NA) of a fiber optic cable is a critical parameter that indicates its light-gathering ability. It quantifies how effectively a fiber can collect light from the surrounding environment and transmit it down the core. A higher NA means that the fiber can accept light at a wider range of angles, which enhances the efficiency of light transmission, especially in applications that require high sensitivity to incoming light.

NA is mathematically defined as the sine of the maximum angle of acceptance (θ) of the light that can enter the fiber divided by the refractive index of the core (n_core). This relationship highlights that the NA is intrinsically linked to the optical properties of the fiber, allowing engineers to assess and design fibers suited for specific applications, such as telecommunications and sensors.

Understanding the NA is crucial for optimizing the performance of fiber optic systems, as it directly influences the fiber's ability to function in different lighting environments and configurations.