WCA July 2019

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 ). The submarine cable was laid from the landing site towards open seas (direct landing installation) within specified pulling tension ( Figure 5 ). Water depth is 0 to 3,800m as shown on the Bottom Profile of Figure 6 . The cable tension is carefully monitored during installation to control the touch down point as to follow the bottom profile. Therefore, cable tension values change due to the various parameters (cable weight in water, catenary length, laying angle, ship speed, sea swell, etc) that are measured to drive cable-handling equipment on board. The cable tension has its highest value on top of the sheath, where also cable elongation is large and the risk of affecting the transmission properties of the fibre is a concern. Optical attenuation measurements were conducted by cut-back method and two-way OTDR during and after the cable laying operation.

Repeater

Shore-Side

Sea-Side

Loop Splice

❍ ❍ Figure 3 : Submarine cable configuration at factory (before loading)

Repeater

Shore-Side

Sea-Side

Loop Splice

❍ ❍ Figure 4 : Submarine cable configuration as laid

Optical Attenuation (dB/km) @1,550nm @1,550nm

Remarks

At Factory 0.153

0.154 0.156 0.154 0.154

Reference

During Laying

0.154

including JB-SpL

After Laying 0.152 After 5 days 0.152

including JB-SpL including JB-SpL

❍ ❍ Table 1 : Optical attenuation results

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 .

❍ ❍ Figure 5 : Cable tension

❍ ❍ Figure 6 : Bottom profile

Bottom Profile

Cable Tension

DA SA LWS

Repeater Touch Down

Ship’s Heading Change

Transition (SA >LWS)

Transition (DA >SA)

Repeater Launch

Water Depth [m]

Cable Tension [KN]

Repeater

Distance from Beach [km]

55

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Wire & Cable ASIA – July/August 2019