WCA September 2020

Figure 4 shows the results of OTDR measurements of three spans of installed and spliced OPGW cable. Despite the fact that the cable was installed by several construction companies, and deployment, splicing and measurements were done by different technicians, we observed similar attenuation distribution for 48 cabled fibres for all three spans. The mean attenuation at 1,550nm wavelength was 0.165 dB/km, but only a few of the 48 fibres showed the maximum attenuation close to 0.168 dB/km. Then we calculated the attenuation distribution of installed cable for the entire 500 km transmission line by taking the weighted average of three previously measured cable sections. This data is presented in Figure 5 . One can see that the distribution becomes tighter as the number of concatenated lengths increases. The mean attenuation among all 48 fibres remains the same – around 0.165 dB/km – but the maximum attenuation decreased to 0.167 dB/km. Taking into account that ultra-low loss fibres with the mean attenuation of about 0.163 dB/km were used in OPGW cable to build 500 km transmission line, we can conclude that after the cable production, installation and splicing attenuation has increased slightly – from 0.002 dB/km to 0.004 dB/km. We believe that such an increase can be largely attributed to splicing. For example, an average splice loss for G.652 single-mode fibres is 0.02 to 0.03 dB [5] . With an average cable length of 6 km used in our study, this results in 0.003 to 0.005 dB/ km attenuation increase (if normalised per km), which is consistent with the attenuation increase observed in our measurements. Figure 6 shows how the attenuation changed after approximately one year after the deployment of the cable. No significant attenuation increase was observed, and most of the fibres showed an even lower attenuation compared to the measurements taken right after the installation. We believe that attenuation decrease can be explained by fibre relaxation in the cable after the installation, and corresponding reduction in microbend induced losses. The highest attenuation increase was less than 0.001 dB/km, which is close to the accuracy limit of OTDR. 5 Conclusions OPGW cable with ITU-T G.652-compliant ultra-low loss fibres used in this work showed excellent performance during the temperature cycling test in the lab, after field deployment and one year after deployment. Attenuation increase of the cable during the temperature cycling test was less than 0.005 dB/km at 1,550nm for temperatures in the -40°C to +85°C range. The mean value of attenuation in the installed cables including splice losses was measured to be 0.165 dB/km at 1,550nm. No significant attenuation increase was found in one year after deployment of cable. Cable design, installation procedures and low-loss optical fibre characteristics were found to be essential in achieving 100+ G unrepeatered signal transmission at distances longer than 500 km.

500 OPGW cable line with 48 Ultra-Low Loss Fibres

Attenuation at 1550nm(dB/km)

❍ ❍ Figure 5 : Attenuation distribution at 1,550nm for 500 km of deployed OPGW cables with ultra-low loss fibres. Splice losses are included

❍ ❍ Figure 6 : Attenuation change after one year of exploitation of OPGW cable with ultra-low loss fibres

6 Acknowledgements Special thanks to Igor Frolov from Saranskkabel-Optika and Test Laboratory Opticenergo for their contribution to performing the test measurements. 7 References [1] V Gainov et al, “Record 500 km unrepeated 1 Tbit/s (10x100G) transmission over an ultra-low loss fiber”, Optics Express 2014 Vol.22, No.19 [2] Do-il Chang et al, “Ultra-long unrepeated transmission over 607 km at 100G and 632 km at 10G”, Optics Express 2015 Vol.23, No.19 [3] Do-il Chang et al, “Ultra-Low Loss Fiber and advanced Raman amplification deliver record unrepeated 100G transmission”, SubOptic 2016

[4] IEC 60793-2-50 Table 11 [5] ITU-T G. Sup.39_2016

Courtesy of IWCS Cable & Connectivity Symposium, Charlotte, North Carolina, USA, September/October 2019.

Corning SNG Moscow, Russia korotkovnm@corning.com www.corning.com Saranskkabel-Optikа

Saransk, Russia opgw@sarko.ru www.sarko.ru

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Wire & Cable ASIA – September/October 2020