Quickly Identify Locations of Faults in Optical TransmissionsFault Diagnosis Technology that Uses the Optical Signal Characteristics to Proactively Identify Failure Locations in Optical PathsNTT Network Innovation Centers

Maintenance operations carried out on optical transmission networks require the rapid restoration of equipment in the event of faults. However, the restoration may take a long time in the cases where fault diagnosis performed by monitoring alarms or checking logs cannot identify the fault point. In order to solve this problem, we are moving forward with research into fault diagnosis technologies that utilize a variety of performance data of optical signals acquired from optical transmission devices. This technology analyzes changes of optical signal characteristics stemming from anomalies occurred in transmission paths, and proactively identifies the location of the faults.

In core optical transmission networks, optical cross-connects and optical amplifiers are connected in multiple stages in order to provide long-distance, multi-direction transmission. These devices do not have monitor functions for the details of optical signal characteristics, and faults occurred in the middle of the transmission path may only be detected at the receiving end of the optical path (client signal transmission/receiving module). In these cases, to determine at which part of the transmission path the optical signal degraded is not easy by using alarm information or device logs, and identifying the location of the fault may take a long time.

• Even if identification of the fault location performed by monitoring alarms or checking logs is difficult, this system enables rapid diagnosis of faults.
• Analysis of the performance information of optical signals with a focus on changes in the optical signal characteristics enables proactive detection of degradation in device performance and malfunction due to aging and environmental changes, along with estimation of the location of the fault.
• Formerly, isolating these faults took a long time, but this advancement makes it possible to reduce the work load of maintenance person, and the time needed to restore the equipment.

• Optical transmission systems fault isolation

NTT Network Innovation Centers – Transport System Project