Fiber NA Calculator
Calculate numerical aperture, acceptance angle, and relative index difference for optical fibers from core and cladding refractive indices.
Numerical aperture (NA) of an optical fiber describes its light-gathering ability — specifically, the maximum cone half-angle of light that will be guided by total internal reflection. NA = √(n₁² − n₂²), where n₁ is the core index and n₂ is the cladding index. A higher NA accepts a wider cone of input light but supports more guided modes and typically has greater chromatic dispersion. This calculator derives NA, acceptance half-angle, and relative index difference Δ from core and cladding refractive indices. Presets are provided for common single-mode, multimode, and polarization-maintaining fiber types. Use this tool when matching a launch objective to a fiber or evaluating coupling efficiency.