# Mode field diameter calculator

Input

Output

μm

$MFD = 2a\left(0.65 + \dfrac{1.619}{V^{3/2}} + \dfrac{2.879}{V^6}\right)$
where $V$ is the normalized frequency
$V = \dfrac{2\pi}{\lambda}a\mathrm{NA}$
and $\lambda$ is the signal wavelength, $a$ is the fiber core radius and $\mathrm{NA}$ is the core numerical aperture.