Network Monitoring Center provides 'first aid' during network disruptions

KLIC notification

At Eurofiber's NMC, the alarm bells ring immediately when excavation damage occurs, says Peter Castenmiller, who leads the fifteen-person team that mans the NMC in shifts. "Let me start by saying that everyone tries to prevent damage to cables — whether fiber optic or electrical — caused by digging. In the Netherlands, it is legally required that anyone planning to dig must first submit a so-called 'KLIC notification' to the Land Registry. That body then informs the applicant whether and which cables and pipes are buried at that location. But sometimes a company is digging and accidentally hits a cable or pipe anyway."

Keeping a close watch at the NMC

When a digging incident occurs, Eurofiber's NMC staff receive an immediate alert. For managed services such as Ethernet VPN, a disruption is automatically displayed on the screens. For dark fiber connections that an organization lights and manages itself, the notification comes from the customer. "As soon as we have a rough idea of where the outage is, we can determine which customers are and aren't affected," says Castenmiller. "We then keep them informed about the progress of the repair work — every hour, by email or phone — so they know where we are in the process. We keep going until it's resolved, even if that means working until three in the morning."

Where exactly is the break?

Meanwhile, the investigation begins at the NMC. Peter Castenmiller: "We want to know exactly where the break in the cable is. To find it, we first use cross-referencing on the network to pinpoint the geographical location of the disruption. We then apply a technology called Optical Time Domain Reflection, which allows us to locate the exact spot. It's a technical story, but it's based on the fact that light travels through a fiber optic cable at a specific speed. You send a pulse from the start of the fiber connection. Every impurity and break in the connection causes the light to 'reflect' back to the starting point. The time this takes tells us how far from the starting point the break is located. We then feed that into our geographic information system and can send the engineer to the exact location — for example, 7.3 kilometers from the measurement's starting point."

Repair work

Once the field engineer has arrived at the exact location of the excavation damage, the repair work can begin. Peter Castenmiller: "The engineer looks for visible disturbances in the ground surface. Once that's found, the repairs begin. First, the damaged area is excavated so the duct can be seen and accessed. The two endpoints of the duct are then located, and the fiber optic cable is pulled out. The duct is repaired, a new fiber optic cable is blown through it, and finally the fiber optic cables are spliced back together."

Final check

Once the on-site work is complete, Eurofiber staff at the NMC test whether the connection is indeed working optimally again. Castenmiller: "We check, for example, whether the attenuation is the same as it was before the disruption. Light traveling through a fiber optic cable loses strength the further it travels. Intermediate splices also reduce the 'optical power.' We call this attenuation. If the attenuation is not back to its previous values, we continue troubleshooting. Once the connection is working optimally again, we contact the customers to verify that everything is working on their end as well."

Resolved within eight hours

"Eurofiber aims to keep disruptions in its fiber optic network as short as possible. We guarantee our customers that outages are resolved within eight hours. We achieve this in 95 to 99 percent of cases. The instances where we don't are attributable to external parties. We sometimes encounter situations where a contractor on a construction site reports at five in the afternoon that they've hit a cable. By that time, the construction workers have already gone home and there's no one available to open the gate to the site for us. That causes delays. It also happens that a high-voltage cable is located in the same cable trench as our cables. The power then has to be cut first, and that can unfortunately take some time — you're then dependent on a third party such as a construction company or a grid operator."

Unforeseen circumstances

Sometimes the causes of a network disruption are less obvious than an accidental dig. Peter Castenmiller has an example: "There was once an incident at a transmission mast in the middle of a forest. The fiber optic cable running to it had failed at about 400 meters from the mast. Our engineer walked through the forest but saw no disturbance of the ground surface. What turned out to be the cause: it was a slightly older cable with a metal core reinforcing the duct. During a recent thunderstorm, lightning had struck the mast, causing the cable to almost literally 'vaporize' from the impact. Well — you can't see that coming."