# Fiber splice loss calculator

## About this calculator

This calculator computes the splice loss between two single mode fibers assuming Gaussian mode shapes according to Marcuse's equation (see Mode field diameter calculator). The splice loss in dB is computed as

$Loss(dB) = -10\log\left[\dfrac{4 w_1^2 w_2^2}{(w_1^2 + w_2^2)^2}\exp\left(-\dfrac{4\delta^2 + k_0^2 n ^2 w_1^2 w_2^2 \sin^2 \theta}{2(w_1^2 + w_2^2)} \right)\right]$

where $w_1$ and $w_2$ are the mode field radii in fibers 1 and 2, respectively. $\delta$ is the lateral offset between the fibers' cores, $\theta$ is the angular offset between the cores, $k_0=\dfrac{2\pi}{\lambda}$ is the vacuum wave number and $n$ is the refractive index of the fibers' cores.

The splice loss is the same independent of which fiber is the input fiber and which the output fiber. This formula works best for standard fibers with relatively large V-parameters whose mode field can be well approximated as Gaussian.