Introduction to Polarity options for MTP / MPO fibre optics

 Introduction to Polarity options for MTP / MPO fibre optics

Understanding Polarity                

TIA-568-C.0 defines 3 possible polarity methods for maintaining polarity in MTP®/MPO cabling systems. The various methods are described as Method A, Method B and Method C.

These various methods utilise a combination of possible configuration and array alignments, which can be managed in the MTP®/MPO trunk cable, MTP®/MPO cassette and/or equipment patch cords.

It is important that network operators consider the current needs as well as future growth of their network, in terms of speed and density. Selecting a polarity option at the beginning of network design and following the same method throughout the life of the network, will ensure ease of operation and polarity management.

 

Summary of components used for duplex signals

 

 

Summary of components used for parallel signals

 

 

Utilising a common cross-connect cabling method for Methods A, B and C will be explained further in future blog posts. Other cabling methods may be utilised, including direct connection, inter-connection, link extensions, etc. as well as utilising MTP®/MPO fan-outs in the configuration.

Regardless of which cabling configuration is used, the same rules for ensuring the correct polarity apply. Transmit ports on End A must connect to receive ports at End B and vice versa.

In addition, each polarity method utilises different trunk cable types – A, B or C.

 

Type A trunk cable 

Key up to Key down

 

 

Type B trunk cable

Key up to Key up

 

Type C trunk cable

Key up to Key down (pairs flipped)