PMD Fibre Testing

Lightguide Technologies offers a PMD fibre testing service. We use the latest equipment and provide a comprehensive results package on CD.

What is PMD (Polarisation Mode Dispersion)?

Laser transmitters in optical networks transmit each pulse on two axis 90 degrees apart at the same time. If the fibre is not perfectly round, the pulse will be distorted, as each axis of the same pulse arrives at the receiver at a different time, causing the pulse to spread and give errors.

When should I test for PMD?

It is absolutely essential to test for PMD before buying, leasing or renting any dark fibre, otherwise expensive disputes can arise. When upgrading an existing network to higher rates, a PMD test is strongly recommended

What causes PMD?

The major cause of PMD is the asymmetry of the fibre optic strand. This asymmetry is caused by the fibre core being slightly out-of-round, or oval. Fibre asymmetry may be inherent in the fibre from the manufacturing process, or it may be a result of mechanical stress on the deployed fibre. The inherent asymmetries of the fibre are fairly constant over time, while the mechanical stress due to movement of the fibre can vary, resulting in a dynamic aspect to PMD. PMD problems with the network can be tricky to tie down because of the dynamic nature of this problem.