The ever-increasing demand for bandwidth in data centres prompted the development of the mulit-fibre push-on connector (MPO) – compact, pre-terminated links able to handle bandwidth all the way up to 100Gbps – and to date, the only type of connector that is recognised by standards to do so.

The MPO (also known in IEC Standards as an ‘array connector’) was the first commercially available type and is standardised in IEC-61754-7 and EIA/TIA-604-5 (FOCIS 5). MPOs come as 12 or 24 fibre variants in multimode and singlemode and are available from numerous vendors in one format or another.

When mechanical transfer push-on connectors (MTP) came onto the market, it created questions as to the differences between the two. Essentially MTP is an ‘enhanced/high performance’ MPO and is a registered trademark of US Conec, based in Hickory, NC. MTP is fully compliant with IEC-61754-7 and EIA/TIA-604-5 but built to tighter tolerance and offers mechanical and performance advantages over MPO. The MTP design includes a recessed pin clamp and oval spring which ensures a secure spring seat, and greater clearance between the spring and the ribbon cable, reducing the risk of damage to the cable.

The MTP housing is uniquely shaped so that the MT ferrule has increased float while mated, protecting the connector mating from sideways strain and damage (see FIgure 1).
 
The MTP design also includes a removable housing, allowing easy gender changes, geometry verification and re-measuring when required. The MTP also has elliptically-shaped precision guide pins for precision alignment and improved durability. Superior mechanical and optical performance can be achieved (see Figure 2).
 
Figure 3 shows a typical MPO guide pin hole damage after only 50 matings.
 
Figure 4 shows a typical MTP guide pin hole damage after 500 matings.

Over time, the options available for MTP have expanded to include round cable applications as well as the original ribbon housing kits and solutions for harsh environments.

Installers and end-users have also had concerns about interoperability between MPO and MTP. AFC undertook controlled insertion loss tests, examining combinations of MTP and MPO interfaces. These tests showed that there were no issues with mating MTP and MPO but that there was a difference in performance. Results revealed that the more MTP connectors were used in the system, the lower losses were observed; so that a combination of MTP and MPO performed better than MPO-MPO, and MTP-MTP performed better still. 

It’s clear that both systems work but that MTP technology is mechanically and optically superior. In all cases though, inspection and cleaning is critical before mating. In a study by NTT-Advanced Technology, 98% of installers and 80% of network owners reported that issues with connector contamination was the greatest cause of network failure. Contamination can cause ORL and reflection loss, creating error packets in layers 2 and 3, and require data retransmission requests at higher layers – the net result being loss of time, network outages and increased failure rate. The challenge is easily overcome with proactive inspection and cleaning and the clear benefits of reduced network downtime, reduced trouble shooting and optimised signal performance are worth the simple extra step during installation. Always inspect before you connect!

Richard Kaehne has been engaged in the fibre optic industry for over twenty years in senior sales, technical and product management roles. He has been with AFC for over 15 years and is currently their Group Product Manager. Richard also actively participates as a member of the AS fibre optic testing sub committee.

Visit www.afcgroup.com.au.