WCA September 2019

engineers estimate the penetrated location. Figure 4 shows the function of fibre length registration. Cable length registered in the facility management system is a design length. On the other hand, the OTDR waveform shows an actual length. As a result, cable length from the central office to water-penetrated closures does not match completely. The distance correction function is provided to fill the distance gap between the cable route planning information of the facility management system and the OTDR waveform. The correct cable length is updated by registering actual distance every time the engineer works on repairing the underground closure. According to the function, the accuracy of the cable length will be improved gradually along with the increase of the length correction information, once repaired. Repair records of the penetrated closures can be useful for searching locations of water penetration in the future. The important point is that every repair will be finished in the future. By utilising these functions, it will improve the efficiency of tasks in finding penetrated closures. 3.3 Function for searching locations of water penetration Conventional periodic test procedure is shown. 3.4 Repair work management function The conventional repair work is as follows. Since it takes time to find the water-penetrated closures and management of the penetrated closures is complicated, the repair completion rate is only 40 per cent. Until now, it was difficult to prioritise the repair work as NTT did not have the function to manage the penetration time of closures and progress of the repair work. The newly developed system has the function of managing the progress of the closure repair, the penetration time of closures, and fibre-splice type. This function allows engineers to develop efficient repair plans. 4 Conclusions Developed functions of the operation system are automatic periodic testing and distance correction in the facility information database. The newly developed system provides an automatic water penetration test function, cable length database correction function and repair work management function. Through these functions, engineers efficiently perform maintenance, and as a result, the quality of optical communication is maintained. 5 Reference [1] NTT “Financial Results for the Three Months Ended”, 30 th June 2017 [2] Enomoto Y, Izumita H, Mine K, Uruno S, Tomita N, “Design and performance of novel optical fibre distribution and management system with testing function in central office,” Journal of Lightwave Technology, Vol 29, No 12, 15 th June 2011 [3] Nakazawa K, Enomoto Y, Yamane T, Araki N, “Technologies for checking outside optical distribution equipment”, NTT technical review, Vol 7, No 11, November 2009 Courtesy of IWCS Cable and Connectivity Symposium, Rhode Island, USA, October 2018. Strategic Network Management Department NTT East 19-2 Nishi-shinjuku, 3-chome Shinjuku-ku, Tokyo 163-8019, Japan Tel : +81 3 5359 4450 Email : miho.akamatsu@east.ntt.co.jp

Estimate

OTDR result waveform

Linking distance

Route information

Distance correction function

Before

Repaired actual distance 800m

After

❍ ❍ Figure 4 : Function of distance correction

(d) Server : This is installed in a data centre and connected to all the OTMs and the operation terminals by DCN (Data Communication Network). Thanks to the nationwide DCN, it is possible to operate OTMs remotely from every service centre and the head office 3.2 Function for periodical test The conventional periodic test involves the following procedures. The OTMs automatically perform OTDR tests based on the set cycle (eg 90 days). The OTMs detect a bending loss of 2.3 dB or more and extract it as a candidate of water- penetrated cable. Engineers remotely operate the OTMs and monitor OTDR waveform to confirm water penetration. If the loss of 2.3 dB cannot be confirmed, the operator changes OTDR settings such as test wavelength, pulse width, etc, to clarify water-penetration. If there are many penetrated facilities, the next periodic test will start before the last repair work is completed, so the additional test results accumulate, and the data management becomes complicated. The newly developed system provides functions which summarise periodic tests and shows water-penetrated closures in real time. The summarised result is visually shown for easy understanding and engineers can obtain fresh information remotely and receive an alarm with automatically distributed email. Figure 4 shows the procedure of the water penetration test with the newly developed system. In this system, a test cycle is set up. This was set for every 30 days so that it could be repaired within 90 days. The result includes a bending loss by water sensor module and its location. The new system also pays attention to the fibre length. If the length is two per cent shorter or 0.2 km shorter than the last OTDR waveform, the system displays an alarm, and there is the possibility of a broken cable. There are also two points of logic to enhance the efficiency of penetrated facilities search. Engineers compare the optical distribution diagram with the OTDR waveform, and then search locations of water- penetration. In the proposed maintenance system, the OTDR waveform and the facility information are simultaneously displayed. This visualised function helps

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Wire & Cable ASIA – September/October 2019