The Dell Technologies World trade show was a few weeks ago and I attended to represent CABLExpress Skinny-Trunk data center cabling solutions. This year, many attendees asked me various questions about the MPO connector. Why is it used? How is it used? How do I integrate it into my current cabling plant?
These questions are common for me, as I have been in the cabling industry for almost two decades and have answered these same questions many times before. What piqued my interest this time was the increased intensity of the questions asked and scrutiny of my responses. More so than I have ever experienced at a trade show.
Because the MPO connector is now being used in commonly purchased optics, it is more than a curiosity. Users need to know how to integrate it into their cabling plant.
Data center fiber has been dominated by the LC connector for the past 15 years for both Ethernet and Fibre Channel alike. That, however, is changing, and change can be difficult!
Speeds are increasing and multimode fiber cannot transmit enough data over a single fiber to keep up with the speeds that Ethernet and Fibre Channel hardware are running.
To work around this bottleneck, multiple fibers are aggregated in order to transmit higher speeds. For example, using an SR4 QSFP that transmits 40G Ethernet. Instead of (1) fiber being used to send a 40G signal, the QSFP will transmit (4) 10G signals over (4) individual fibers. This allows a 40G signal to be sent and received by the hardware, overcoming the bottleneck that the multimode fiber has. So as the speeds continue to increase, the LC connector will be supplanted by the MPO connector because of its ability to house more fibers (currently up to 72).
To integrate the MPO connector into your existing cabling plants requires careful consideration. There are a few key points that I will touch on below, but I would highly recommend discussing your options with one of our data center architects.
Our team can provide education on the connector as well as how to manage specific challenges that you may incur in this transition. If you want to reach out, you can start here.
One important consideration about this connector is optical polarity. Polarity refers to the assurance that your signal transmission will reach the correct receiver. If the polarity is not correct, you will not have communication between the ports that are being connected. With LC connectors, if a port wasn’t working, you would flip the fibers within the connector on one side. If the port “lit up”, you could move on, you had just fixed the polarity! With (2) fibers, this is relatively easy to do.
With an MPO connector, you are dealing with (12) or more fibers, as well as a connector body; this presents specific challenges in polarity change. In short, it is incrementally more challenging to manage optical polarity with the MPO connector, so it is of the utmost importance to do it right from the start!
We have a great white paper about this topic: Simplify Fiber Optic Cabling Migrations with a Multi-Path System
Next is performance. This applies to all fiber cabling types but becomes even more important when running higher speeds. I would advise anyone purchasing cabling to scrutinize the “Maximum Insertion Loss” of the cable assembly. Insertion loss is a key metric to the performance of the cable. The lower the number of Insertion Loss of your cable, the better performing your cable is.
With higher speeds, the loss tolerances for cabling are more challenging to meet. If tolerances are exceeded, the hardware will not function properly. The MPO, having multiple fibers in a small connector footprint, proposes distinct performance challenges to cable providers. With more connection points (where Loss takes place), it is more difficult to stay within your loss budget for the assembly with an MPO connector than it is for an LC.
Many cable providers will provide “typical” results. This is a gamble I would not recommend anyone taking. Just like a household budget, know where your limit is and stay under it. Providing a typical loss does not guarantee, providing a maximum does. So demand a maximum loss number and match that against your optical budget or prepare yourself and your team for intermittent port errors. Port errors could mean downtime, and nobody wants that!