EuroWire May 2019

Technical Article

Measurement Results of Submarine Cable After Actual Installation By Mizuki Ohara, Daishi Masuda, Masumi Kobiki, Submarine System Plant, OCC Corporation, Kitakyushu, Japan

Abstract The authors obtained attenuation results for submarine cable applying optical fibre with effective area of 150μm 2 , after actual field installation. Attenuation was 0.152dBkm, which is the same value as the “coiled cable” at the factory. 1 Introduction The development towards higher bit rate optical communication systems has been rapidly evolving in recent years and the advances in transmission technologies have increased the level of requirements for each element of the system. For high-capacity long-haul submarine trans- mission systems the deployment of “ultra low loss” and “ultra large effective area” fibres has become a “must” to improve OSNR and system performance. The cabling evaluation and qualification for ultra low loss and ultra large effective area fibres were completed with excellent results. For the deployment of recent high- performance optical fibres over trans- oceanic distances, a few thousand kilo- metres were manufactured and delivered over the 2014-2017 period. One concern about utilising such ultra large effective area optical fibres was macro/micro bending losses introduced during the cabling process. OCC managed to finish mass production of cables and system integration works successfully, supported with results measured on coiled cable that was not in actual installed conditions. In this paper, the authors present the optical attenuation measurement results of submarine cable during/after actual laying operations.

Steel tape

LWS (Light Weight Screened)

Sheath PE

Fibre Water Blocking Compound 3-divided Steel Segment Steel Wire Water Blocking Compound Copper Tube Insulating Sheath PE

Inner Armour Wire

Armour Wire

Outer Serving Outer Armour Wire Inner Serving

Outer Serving

SA (Single Armoured)

DAS (Double Armoured Smart)

▲ ▲ Figure 1 : LW (Light Weight) cable

▲ ▲ Figure 2 : LWS and armoured cable

3 Cable under test The submarine cable was equipped with optical fibre having a large effective area of 150μm 2 . The submarine cable’s mechanical length was approximately 82km and was finished with different types of protection, as depicted in Figure 3 . This cable protection was applied over the same cable core (DAS: 2km, SA: 8km, LWS: 72km). A “loop splice” in the coupling housing of the repeater made the length of fibre under test approximately 165km. At the factory, this submarine cable was manufactured in one piece with inspection conducted at every step of manufacturing to allow tracing of any in-process variation. The submarine cable was coiled in a cable tank with a diameter of 15m, which is similar to that of a cable ship for installation. However, during cable loading operations, this cable had to be cut due to an approaching typhoon, allowing the cable ship to avoid the storm. Finally additional an on-board joint box (JB) was inserted to re-build the cable span ( Figure 4 ).

Prior to installation, submarine cable system performance is generally inspected with C-OTDR and spectrum measurement for the entire system length. This time the most important parameter of submarine cable, which is optical attenuation, was measured during actual deployment conditions, making this study a unique one. 2 Optical submarine cable design SC500 series cable structure’s special features are that the optical fibres are directly cabled into the three divided steel segments tube. To achieve manufacturing of this design, OCC has developed a state-of-the-art fibre insertion technology. The three divided steel segment structure is followed by a layer of stranded high strength steel wires, which is then covered with seam-welded copper tape that serves as both the hermetic barrier against moisture ingress and the power feeding conductor. The LW (Light Weight) cable structure is shown in Figure 1 . The LWS and armoured cable structure are shown in Figure 2 .

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May 2019