WCA July 2019

Optical Attenuation vs Wavelength

1.55μm OTDR results (two-way method)

During Laying After 5 days

At factory After Laying

At factory During Laying

After Laying

After 5 days

Laying after 9 months

Optical Attenuation (dB/km)

Optical Attenuation (dB/km@ 1.55μm)

Wavelength (nm)

❍ ❍ Figure 7 : Optical attenuation vs wavelength

❍ ❍ Figure 8 : 1,550nm OTDR results (two-way method)

4 Measurement results Optical attenuation results are shown in Table 1 . Optical attenuation at the factory, as reference, was measured with the cable coiled and without on-board JB. During/ after laying values include extra optical attenuation due to on-board JB inserted to rebuild span (two splices added). The on-board JB splice loss (two splices) was 0.09dB, evaluated from two-way OTDR traces. Optical spectral attenuation curves at different points of the cable installation are shown in Figure 7 . A small variation (attenuation increase) during laying was confirmed. This change is presumed to be caused by laying tension being applied to the submarine cable section between seabed touch down point and cable ship. In the section where tension/elongation is applied, the condition of optical fibre temporarily changes and sensitively reacts, resulting in the optical attenuation increasing due to microbending occurring when fibres move and compress against each other. After the laying operation, optical spectral attenuation decreased to the same level measured at the factory. Measurements were continually taken for five days after the repeater, where the “loop back splice” is stored, touched the seabed and confirmed that optical spectral attenuation along the entire measurement window was very stable. In the optical attenuation during/after laying operation by OTDR at 1,550nm (C-Band) and 1,625nm (L-Band) was also measured. Measurement results at 1,550nm are shown in Figure 8 . Before shipment of the system measurement, approxi- mately one year passed since cable manufacturing completion, with no increase in optical attenuation confirmed by pre-shipment measurement. Results shown in Figure 7 and Figure 8 were consistent with the ones confirmed at the factory, and no additional reflection point or irregular section appeared during handling of the cable. 5 Conclusion The authors obtained excellent optical attenuation results for submarine cable equipped with optical fibres with an effective area of 150μm 2 after actual laying operations.

Optical attenuation at 1,550nm was 0.152dB/km, the same as the value confirmed on coiled cable at the factory. With all those data sets, it can be confirmed that optical attenuation was very stable throughout the time period from system assembly completion to field installation. Additionally, cable joints and couplings are sufficiently robust to withstand laying and handling without degrading the optical performance of the system. Finally, these results show that the cable design is capable of delivering all the properties of high-end optical fibres to realise high bit rate systems of 100Gb/s and higher. 6 Acknowledgments The authors gratefully acknowledge the system owner, ship operator, landing staff for their cooperation during field measurements and colleagues for their contributions to this paper. 7 References [1] M Sakaguchi et al., “Development of Advanced Small Diameter Submarine Cable” SubOptic2010, EC16 (2010) [2] D Masuda et al., “Mass production results of submarine cable applying “Ultra Low Loss” and “Ultra Large Effective Area” Fibre”, IWCS2016, Section2-Paper3. [3] Y Tamura et al., “Lowest-Ever 0.1419-dB/km Loss Optical Fiber”, OFC 2017 paper Th5D.1 [4] V Kamalov et al., “Faster open submarine cable”, ECOC 2017, paper Th.2.E.5. Paper courtesy of proceedings at the 67 th IWCS Conference, Providence, Rhode Island, October 2018.

Submarine System Plant OCC Corporation 1-505-2, Hibiki-machi, Wakamatsu-ku, Kitakyushu, 808-0021 Japan Tel : +81 93 751 6500 Email : ohara@occip.com

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Wire & Cable ASIA – July/August 2019