| Features | Applications | Options |
|---|---|---|
| High speed | Polarisation switching | 1300 nm band versions |
| Low insertion loss | Polatisation scrambling | Choice of optical connectors |
| Hermetic package |
LASER COMPONENTS, the dedicated UK and Ireland suppliers for Photline Technologies, is pleased to announce the new PS-LN polarisation switch.
These polarisation switches are integrated optics waveguide devices that switch the polarisation state of an input light between two linear orthogonal output states at frequencies of up to 10GHz. Practically, the output light in polarisation maintaining fibres and components is transmitted on either the fast or slow axis, therefore this switch is operational as a TE to TM converter.
In principle the PS-LN rotators are based on a birefringent LiNb03 phase modulator where the waveguide is propagated at 45° of its main axis. The input state of polarisation (SOP) is thus split up in two orthogonal TE and TM polarisation states. When the RF modulation signal is applied via the components electrodes, an optical path difference between the TE and TM components is produced, resulting in a new state of polarisation (SOP) for the output light.
The PS-LN effectively acts as a wave plate with user adjustable delay. When a modulation signal with properly selected peak levels is applied to a modulator, the input polarised light is exiting either in an unchanged direction, or rotated by 90°. The two directions are matched with the main axis of the output optical PM fibre and the PS-LN thus operates as a slow/fast axis switch. Ultimately, the phase modulation signal can be adjusted to provide a highly linear SOP on either axis of the output fibre. This polarisation rotation provides an efficient means for high speed polarisation switching or polarisation scrambling.
The linearly polarised light entering the modulator at 45° of the crystal’s optical axis can be resolved into two waves, parallel and perpendicular. In the LiNb03 crystal, the parallel wave propagates slightly slower than the perpendicular one, and the speed is adjusted by the voltage applied to the modulator. At the end side of the crystal, the parallel wave is exactly half of a wavelength delayed relative to the perpendicular wave, and the resulting combination is orthogonally polarised compared to the entrance state.
