Challenges of MPO Cables

MPO trunk cables (see the picture below) have become the common cabling solution for the ever increasing data center bandwidth requirements. The MPO fiber cable links have the features of parallel transmission and they are compact, pre-terminated, able to handle bandwidth all the way up to 100 Gbps, and even plug and play by design. The testing, certification and migration of the MPO fiber cables could be a nightmare though they have these advantages. This article will focus on the MPO cables testing in the data center.

The standard testing process of fiber cables can be time consuming, error prone, and once you throw polarity of all 12 fiber connections into the mix, almost a hit-and-miss manual affair. And if you migrate from 10 Gbps to 40/100 Gbps, you need to test and validate performance all over again.Challenges of MPO Cables

In order to get a better understanding about the challenges of MPO cable validation, it is essential to understand MPO cables and how they are tested. An MPO connection is about the size of a fingernail and contains 12 optical fibers, each less than the diameter of a human hair, and each one needs to be tested separately. The actual fiber test is quick enough, typically under 10 seconds per fiber once you’re in process.

The challenge is that pre-terminated fiber is only guaranteed good as it exists in the manufacturer’s factory. It must then be transported, stored, and later bent and pulled during installation in the data center. All kinds of performance uncertainties are introduced before fiber cables are deployed. Proper testing of pre-terminated cables after installation is the only way to guarantee performance in a live application. Testing and determining fiber polarity is another challenge. The simple purpose of any polarity scheme is to provide a continuous connection from the link’s transmitter to the link’s receiver. For array connectors, TIA-568-C.0 defines three methods to accomplish this: Methods A, B and C. Deployment mistakes are common because these methods require a combination of patch cords with different polarity types.More Bandwidth, More Testing

The use of MPO cables for trunking 10G connections in the data center has steadily risen over the past years. That trunking requires use of a cassette at the end of the MPO cable designed to accommodate legacy equipment connections. Now the 40G and 100G connections are coming on the market. So a migration path has emerged: remove the 10G cassette from the MPO cable and replace it with a bulkhead accommodating a 40G connection. Then it might be possible to remove that bulkhead and do a direct MPO connection for 100 Gbps.

The problem is that while this migration strategy is an efficient way to leverage the existing cabling, in comparison to 10G connection, the 40G and 100G standards call for different optical technology (parallel optics) and tighter loss parameters. In all, you need to verify the links to ensure the performance delivery the organization requires when you have a migration for your network.Proper MPO Testing

What would a proper MPO test look like The answer is simple. Test all 12 fibers—the whole cable—simultaneously and comprehensively (including loss, polarity). That sort of test capability changes the fiber landscape, enabling installers and technicians to efficiently validate and troubleshoot fiber—flying through the process by tackling an entire 12-fiber cable trunk with the push of a button.

The tools to perform this type of test are emerging on the market, and promise to reduce the time and labor costs up to 95% over individual fiber tests. Characteristics to look for in such a tool include the following parts.

• An onboard MPO connector to eliminate the complexity and manual calculations associated with a fan-out cord.
• A single “Scan All” test function that delivers visual verification via an intuitive interface for all 12 MPO fibers in a connector.
• Built-in polarity verification for end-to-end connectivity of MPO trunk cables.
• “Select Individual Fiber” function that enables the user to troubleshoot a single fiber with more precision.

Demand for fast and reliable delivery of critical applications is driving data center technology to evolve at an ever increasing pace. And the insatiable need for bandwidth ensures that the integrity of the data center has become inextricably linked to the strength of the fiber cabling infrastructure. The growing use of MPO trunk cables means that it’s time to stop the cumbersome verification of individual fibers. After all, it’s a single MPO connection. You should be able to test the MPO connection as a whole.