Invisible WDB in the IDM network are getting visible in NOC
- 01 Mar 2017
The IDM network, which has total 3,680 km of fiber optic network, 42 backbone nodes, and 308 distribution nodes, had been suffered from no visibility of passive only distribution links and nodes(refers to WDB). Even the cable was damaged by third party, the network operation center could not monitor due to the limited architecture of the IDM network. In usual, active nodes could be monitored by checking connection status in various methods which include PING at every period. However, over the half of the distribution nodes of the IDM were passive only node which means there is no active devices to react PING, even no electricity. Therefore, the operation center could not monitor the status of the node and relations.
In order to overcome the invisibility of WDB nodes and relations, KBTO developed a new method to monitor WDB nodes in real-time. Figure 1. shows that current implementation status of the WDB and its related backbone nodes. As you can see, WDB nodes are connected in fiber networks between ODFs with 12 cores, but no fibers are connected to active networks. Because there is no light in the fiber, so there is no way to monitor the status of the fiber.
Figure 1. Current status of invisible WDB nodes (passive only and open circuit)
KBTO studied and found out two possible ways to make visible WDB nodes. The first one is most powerful solution by measuring the status of the fiber using OTDR periodically. Since OTDR can work in open circuit, the status of fibers could be periodically measured. In addition, the OTDR method is typical, so there are enough documentations and solutions like automatic and period measurements and multi core measurements. Suppose that if there is only a few fibers to monitor, this method could be adopted for the IDM network. However, as noted above, the number of WDB nodes that should be monitored are over 150, and distributed all arounds of the Mazovian voivodship. In addition, the ODTR equipment is quite expensive. Therefore, KBTO selects the other method to make a loop back of fibers.
Figure 2 shows details of the second method – we call it Loop-B. Because we have at least 12 cores to the distribution network, we will make a loop using two cores and put it in the routers in the backbone node. In backbone routers, we set up a loop-back connection using two dark fibers to each distribution type B node to monitor cables at the far end to create a constant optical circuit that originates at the backbone router, travels the length of the cable to the loopback point which is distribution type B node, travels back the length of the cable, and terminates back at the backbone router. Now, the problem gets very simple. The operation center only needs to monitor the port that can transmit and receive the light. If the optical cable cut, the light would be lost, so the link status of the port should be down. In that case, the technicians could be notified by the status using any monitoring solution that can monitor each port.
Figure 2. Making visibility to WDB nodes (passive only but closed circuit)
KBTO now expect that this improvement dramatically decreases the response time of cable damage incidents and allows better localization of the damage for non-monitored sections of the IDM network. Thanks to loop-back dark fibers, each cable damage can be immediately recognized by the monitoring system and will be notified to the KBTO Technical Department in various methods. Therefore, the reaction time of cable damages by our technical department should be dramatically decreased, that results increase of resilience, robustness and maintenance of the infrastructure.