WCA September 2020

Temperature cycling test of OPGW cable with ultra-low loss fibres

Attenuation dB/km

Temperature °C

❍ ❍ Figure 3 : Temperature cycling test of OPGW cable with ultra-low loss fibres

❍ ❍ Figure 2 : The climatic chamber with the cable sample

Reference attenuation dB/km

Max attenuation dB/km

Delta dB/km 0.005 0.005

Fibre specification* dB/km

Set of fibres

1 2

0.169 0.163

0.174 0.168

<0.05

<0.05 *Note: fibre itself exceeds specification for wider temperature range (-60°C to +85°C) and in cable ❍ ❍ Table 1 : Attenuation increase at 1,550nm during temperature cycling test at temperature ranging from -40°C to +85°C

4 Results Figure 3 shows attenuation changes at 1,550nm for two fibre bundles during the temperature cycling test for all three cycles. During this test, no significant differences in attenuation performance were observed between the two fibre bundles. The maximum attenuation increase for both fibre sets during three cycles did not exceed 0.005 dB/km, which is well within the desired limit of 0.01 dB/km (as noted earlier) and is far from the specification limit of 0.05 dB/km [4] . We believe that this measurement result indicates that the chosen OPGW cable design is suitable for ultra-long haul applications with strong optical budget limitations. Since temperature cycle test represents a good proxy for long-term cable performance in the field, we expect similar attenuation variations during cable lifetime. The summary of the data during the temperature cycle test is shown in Table 1 . ❍ ❍ Figure 4 : Attenuation distribution at 1,550nm of deployed cables with ultra-low loss fibres for three 150 km spans. Splice losses are included

relaxation at each measurement point. Temperature range was from -40°C to +85°C for each cycle, as it was required by the customer and the application area environment. Three cycles have been carried out in this test. In our set-up, 48 ultra-low loss fibres were combined in two bundles. Fibres from each bundle were spliced together to provide better accuracy for OTDR measurements of attenuation changes during the test, and each bundle consisted of more than 20 different fibre samples. This set-up was used to accurately reflect real long-haul terrestrial cable deployment conditions that typically contain a large number of spliced cable sections. The two bundles were deliberately designed to represent the upper end of ultra-low loss distribution (first bundle average attenuation 0.169 dB/km at 1,550nm) and the typical attenuation portion (second bundle average attenuation 0.163 dB/km at 1,550nm). This cable test procedure was carried out in full compliance with IEC 60794-1-22 Method F1. 3.2 OTDR measurements of the deployed cable OPGW cable deployed in the field represented a fusion-spliced concatenation of a number of cable lengths varying from 6 to 8 km, and the total cable length was approximately 500 km. Several OTDR devices with dynamic range of 45 dB were used for the measurements. To achieve the desired accuracy and spatial resolution the transmission line was divided in three sections of approximately 150 km, and each section was measured separately from both ends by OTDR. Attenuation measurements of the installed OPGW cable in the field were done twice. The first measurement was carried out straight after the cable deployment. Subsequent OTDR measurements were performed approximately one year after the installation.

OPGW cable with 48 Ultra-Low Loss Fibres Mean value ~ 0,165 dB/km Max value ~ 0,168 dB/km

Attenuation at 1550nm(dB/km)

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Wire & Cable ASIA – September/October 2020