# Logical Inline Reflectors¶

Logical inline reflectors are 2-port devices that reflect a part of the optical power back into the origin waveguide mode. The reflection coefficient can be set independently for both ports, but the transmission in both directions is the same (because of reciprocity).

Logical reflectors don’t have a Layout View, but can be used for circuit simulations. They can also be included to model parasitic inline reflections in a circuit.

The component WaveguideReflector takes two waveguide templates and calculates the reflection from that.

 Reflector Logical reflector: reflects a part of the light and passes on the rest WaveguideReflector Zero-length waveguide reflector: calculates reflection based on the waveguide templates

# Model¶

The circuit model of the simple Reflector has user parameters that can be directly set through the reflection_in and reflection_out properties.

The circuit model of the WaveguideReflector is based on Fresnel reflection, taking the difference in n_eff between the input and output waveguide.

The reflection at the input and output is calculated as:

$r_{in} = \frac{n_{in} - n_{out}}{n_{in} + n_{out}}$
$r_{out} = - \frac{n_{in} - n_{out}}{n_{in} + n_{out}}$