Introduction: MTP Fibre - How to manage polarity in MTP MPO parallel optical fibre links

Introduction: MTP Fibre - How to manage polarity in MTP MPO parallel optical fibre links

Parallel optics and MTP fibre optic cabling have proven to be an excellent solution for delivering 10G, 40G and 100G transmission to enterprise, mobile, data exchange networks and especially within data centre environments. It provides a flexible, high-density option for quickly connecting services and is a reliable high-speed solution for many data networks.

In traditional (serial) optical communications, a transceiver on each end of a link contains one transmitter and one receiver. For example, on a duplex channel, the transmitter on End A communicates with the receiver on End B and another optic fibre is connected between the transmitter on End B and the receiver on End A. This allows for transmission signals to be sent and received over duplex LC links (read more here).

40G and 100G systems require a slightly different configuration with parallel optical communication.
In parallel optical communications, the devices on either end of the link contain multiple transmitters and receivers, which enables multiple fibres or lanes to be used to transmit and receive the same signal. This type of connectivity utilises a multicore cable type design with all fibres aligned in a straight array, in either a 12 fibre or 24 fibre configuration.

To ensure MTP fibre optic systems work with correct polarity, TIA-568-C.0 defines three methods 

The various methods are described as Method A, Method B and Method C and 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.

 

MTP Fibre | Polarity Method A – Parallel Optics (40G) Example

  • Key up to key down adaptors required for mated connection in between MTP®/MPO trunks (Type A).
  • Utilises MTP®/MPO bulkhead adaptors, instead of MTP®/MPO to LC breakout modules in the patch panel.
  • One type A and one type B array patch cord must be used at each end of the link to connect to active equipment.
  • Mated connections at type A adaptors must contain male to female interfaces to ensure correct array alignment.

MTP Fibre | Polarity Method B – Parallel Optics (40G) Example

  • Utilises MTP®/MPO type B cables and adaptor bulkheads throughout the entire link.
  • Utilises MTP®/MPO bulkhead adaptors, instead of MTP®/MPO to LC breakout modules in the patch panel.
  • Key up to key up positioning all throughout the link ensures correct polarity and alignment.
  • Utilises type B array trunk cable and patch cords (key up to key up).

Array patch cords for 100G systems with 24 Fibre MTP®/MPO transceiver ports

Some 100G transmission equipment utilise a 1 x 24F MTP®/MPO port, instead of 2 x 12F ports for send and receive. In these instances, a 24F ferrule MTP®/MPO connector is required to connect to the equipment. The opposite end is generally divided into separate 12F MTP®/MPO connectors, which connect to bulkhead adaptors and to the MTP®/MPO trunk cable.

The various configuration options are listed below.

MTP Fibre | Polarity Method A

MTP Fibre | Polarity Method B

  MTP Fibre | Polarity Method C

MTP Fibre Polarity – Conclusion

When managing the polarity in MTP / MPO parallel optical fibre links (40G and 100G) 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.

Read more about the HypaFOX MTP MPO solution here