In-line polariser
An in-line fibre polariser passes the polarisation along its axis and weakens the crossed one by its extinction.
Ports
Ports 1 and 2, one each side.
The model
For an axis at \(\theta\) from s and an extinction \(X\) (dB),
\[\mathbf M = a\,\mathbf R(\theta)\begin{pmatrix} 1 & 0 \\ 0 & \varepsilon \end{pmatrix}\mathbf R(-\theta), \qquad \varepsilon = 10^{-X/20},\quad a = 10^{-\ell/20},\]with \(\ell\) its insertion loss, \(\mathbf S_{12} = \mathbf M\) and back \(\mathbf S_{21} = \mathbf M^{\mathsf T}\). Being symmetric, \(\mathbf M\) is its own transpose, so it is the same both ways. The crossed polarisation’s power is passed at \(10^{-X/10}\).
Settings
| Field | Default | Meaning |
|---|---|---|
axis | 0 | Axis (° from s) |
extinction | 30 | Extinction (dB) |
loss | 0.5 | Insertion loss (dB) |
From the tool's own tables, file format version 1: the names are those in a .jekray file.
Assumptions
- The extinction and loss are flat in wavelength.
- The fibres either side are taken to hold polarisation; standard fibre as laid scrambles it (see Fibre optics: along a fibre).
Related
- Polarisation beam splitter.
- Polarisation controller.
- Polariser, the free-space polariser.