EuroWire March 2022

Technical Article

conditions during installation, the cable was provided with bent portions at R 360mm x 10 places and the test was conducted with both ends connected within the closure. A three-cycle temperature cycling test was carried out on the 576F cable by holding it from 0°C to 70°C for six hours, and the maximum loss increase was within 0.15dB/km, which is a favourable level for practical use. The waterproof properties were also evaluated, and good results were obtained. 3.3 Blown installation performances A blowing test of the 576F cable was conducted. Figure 5 shows the schematic diagram of the route of the microduct used for the blowing test. Using a microduct of 14mm inner diameter and 18mm outer diameter, we conducted the test with the bending radius of the corner and the flap portion set to 1m. Figure 6 shows the blowing distance at the time of the blowing test. As a result, it was possible to blow the 576F cable to 430m, while maintaining a speed of 60m/min. Further, we measured the transmission losses after installation, and confirmed the transmission loss value was favourable even after installation ( Table 3 ). We are also planning to conduct the experiment in a longer distance route.

Rollable ribbon

Bundling tape

Figure 3 : Bundled unit

Rip cord

144-fibre unit

Water-absorbent, non-woven fabric

Sheath Strength member

Figure 4 : Cable structure

2.2 Bundled unit Figure 3 shows the structure of the bundled unit. Taking a 144F unit made by bundling 12 counts of 12F ribbons as one unit, a 576F cable was constructed from four such units. To identify each unit, a plastic tape was spirally wound around 12 ribbons such that the unit bundles do not collapse easily. By adjusting the winding pitch of the plastic tape, a bundling sense was maintained, thus facilitating its sorting from other units. Further, the colours of the plastic tapes were changed so that the unit number could be easily identified. 2.3 Cable Figure 4 shows the structure of the cable. Generally, most conventional microcables adopt a loose tube structure where a strengthmember is disposed at the centre. In this study, to realise a cable with higher density and lighter weight, four 144F units were assembled around a single strength member placed at the centre, without using loose tubes. The cable was constructed by covering the cable core with a water-absorbent, non-woven fabric for waterproofing and further covering it with black polyethylene together with two rip cords. Since the cable can be easily dismantled by using the rip cords, and since it is an all-dry structure that does not use jelly inside, the workability during laying operation is better than the conventional loose tube cables. The outer diameter of the developed 576F cable is 10.2mm, and it can be installed in a microduct of 14mm inner diameter. Further, as its mass was 66kg/km, it is understood that weight reduction has been realised.

Condition

Result

Tensile

IEC 60794-1-21 Load: 500N

< 0.10dB

Crush

IEC 60794-1-21 Load: 500N/100mm Holding time: 1 min

< 0.10dB

Impact

IEC 60794-1-21 20N x 1m

< 0.10dB

Bend

IEC60794-1-21 Diameter of mandrel: 20 x cable diameter Number of turns: 5 Number of cycles: 3

< 0.10dB

Repeated bending IEC 60794-1-21 Sheave diameter: 20 x cable diameter Cycle: 25

< 0.10dB

Torsion

IEC 60794-1-21 ±90 deg/m Cycle: 3

< 0.10dB

Table 1 : Results of the evaluation of mechanical characteristics

Condition

Result

3 Characteristics 3.1 Mechanical characteristics

Temperature cycling IEC 60794-1-22 0°C to 70°C

Holding time: six hours for each temperature Cycle: 3 Bending radius: R 360mm Cable is jointed by closure during the test

< 0.15dB/km

Table 1 shows the test results of the mechanical characteristics of the 576F cable. The loss fluctuation during the mechanical characteristic tests was measured at 1,550nm. In all the tests, favourable results were obtained. 3.2 Environmental characteristics We evaluated the environmental characteristics of the 576F cable and the results are shown in Table 2 . In the evaluation of the temperature characteristics of the 576F cable, to simulate the

Water penetration IEC 60974-1-22

Pure water, length of water head 1m, 24h

< 5m

Table 2 : Results of the evaluation of environmental characteristics

62

www.read-eurowire.com

March 2022