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Step Index Fiber Numerical Aperture Calculator
Check numerical aperture from core and cladding refractive indices. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Step-index fiber numerical aperture NA
Enter values and select Calculate.
NA = √(n_core² − n_clad²)
Assumptions
Use n_core>n_clad>0 and a step-index geometric-optics model. The result is not identical to a manufacturer's far-field intensity measurement of NA. An acceptance angle in air is not returned.
Displayed values are floating-point approximations. Measurement uncertainty and design safety factors are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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