Spring 2018 Optical Connections Magazine


networks speed up we need to cram more and more information into the fiber optic line,” says Connolly. “This results in complex schemes, whether it is parallel optics or trying to push more data on a single line. New testing methods and technological advancements are required to take advantage of increasing speeds.” Brooks. “But 400G has got some huge challenges”. The leap from 10G, 40G and 100G to 200G and 400G has forced a switch from NRZ modulation to PAM-4, he says, as well as the need for more powerful FEC (Forward Error Correction) to combat noise and reduce packet loss, which in turn bring their own thermal challenges. “The initial 400G modules aren’t 3W watts, they aren’t 8W, they are going to be 12-14W each.” Add them all together and that’s at least 500W per board, probably nearly double that, says Brooks, with all the cooling requirements that kind of power brings. Interoperability is also an issue, he says. “One of the most important things for ethernet is interop. It’s critical that we still hold that principle for 400G, so another big part of test and measurement is making sure that the margin is there to allow interop. That’s a major challenge for test and measurement.” For Olivier Tremblay-Lavoie, Team Manager - Marketing Campaign Management at Exfo, applications for 400G are in the early stages but expanding rapidly. “An interesting option for them is the availability of a same test solution that can be used in the lab, but also reach the field applications, so they can test as well in trials under real network conditions and trac, using the exact same tool.” challenge for test and measurement is to respond and keep up. “Network and test equipment costs increase dramatically as the transmission speeds increase from 40 to 100 to 400G even if the overall cost per transmission bit decreases,” says Richard Jensen, VP Program Management and Architecture at Huber+Suhner Polatis. Jensen sees two main trends emerging when it comes to test and measurement “With all new technology there’s a whole ecosystem impact,” says TEST TRENDS As networks become faster, the

Viavi’s CellAdvisor JD745B base station analyzer.

in low latency systems. The first, he says, is the greater use of optical switching. “Optical switching technology has matured over the last 10-plus years and costs are lowering as volumes increase. Customers want more flexibility to automate their product and network testing and they need to do more in a shorter amount of time. The trends are to try to do as much as you can optically.” Optical switching brings with it a raft of advantages in certain scenarios, says Jensen, allowing test and measurement customers to: share expensive test equipment between more products; automate testing to get higher equipment utilisation and lower costs; and get more equipment costs to lower. It’s also greener, taking up less space and using less power than OEO (optical- electrical-optical) equipment, making it more attractive to many customers and potentially addressing the thermal issue highlighted by Brooks. Its capacity for direct fibre switching also gives it an advantage, allowing people to test dierent configurations, or mimic customers’ network configurations. It’s useful both pre-deployment and in live networks, he says, where it can help as customers in the monitoring aspect of test and measurement. “People want to get as much utilisation as they can,” says Jensen. “People want

to be able to share equipment, run 24/7 and automate the testing.” In essence, it’s one way of future-proofing test and measurement, he says. “People don’t want to have to replace their test equipment every time they raise the bit rate. If every time you increase the bitrate you have to tear out all the cards and replace them it gets very expensive. The trends are as they go higher in speeds are that people are using more all-optical switching. It takes up less space, uses less power and it saves money”. The second trend is more demand for Software Defined Network interfaces, says Jensen. “Software Defined Networking (SDN) gives them the unprecedented monitoring and control of both equipment and network management that allows them to take full advantage of an optical switches to create a flexible optical network layer.” WHAT NEXT? While test and measurement is addressing the challenges that come alongside an ever-increasing demand for speed and low latency, it’s not a done deal, says Brooks, especially when every new development comes with a demand for lower costs. “I don’t think it’s a slam dunk, it’s a big challenge,” he says. A development such as 400G brings with it the need for specialist test and measurement tools, he says, though there is the possibility to re-proposition specialist tools developed elsewhere to analyse the behaviour of 400G networks - something VIAVI has been doing. “We are still in the very nascent stages of things so it’s very exciting, but the challenge shouldn’t be underestimated,” says Brooks. “However, to echo a quote from Irish sports journalist Con Houlihan, we’re making all the right mistakes, and I think that’s where the industry is today.”

Supported by SDNs, Polatis’s Series 6000 Optical Switch enables low latency, virtual cloud services in hybrid packet- optical data centres. Image: H&S / Polatis.


| ISSUE 12 | Q1 2018


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