How high and low temperature affect newtork cables?

The world is geographically diverse, with different temperature zones distributed from south to north, resulting in significant temperature variations between the north and south, as well as between summer and winter. Therefore, when selecting materials for integrated wiring, it is crucial to consider the lowest and highest temperatures of the wiring location. Choosing cables that can function under both the highest and lowest temperatures is essential to avoid rework and damage.

Extreme temperatures in the Northern Hemisphere can drop below -20℃ in January and rise to around 50℃ in July. Therefore, we set the test environment temperatures to -20℃ and 60℃ to conduct high and low-temperature tests on the cables.

To study the impact of high and low temperatures on cable transmission performance, we placed commonly used cables from the market in a high and low-temperature machine to simulate the effects of high and low temperatures on network cable transmission performance. Tests were conducted on the network cables at -20℃ and 60℃.

Initially, at a conventional 20℃, we performed Fluke permanent link tests on Category 5e engineering cables and standard network cables.

Fluke Test Results for Engineering Cables and Standard Cables at 20 degrees Celsius

 

Both types of cables passed the Fluke test, meeting the required transmission performance standards.

Next, we tested the transmission performance of the two types of cables at -20℃.

Using professional Fluke cable testing equipment in this environment, we simulated the acceptance testing of cables at -20℃. The test results showed that both types of cables passed the Fluke permanent link test.

From the test results, we observed that while both cables passed, their transmission performance parameters differed. We then conducted a quantitative analysis of these parameters.

The test results showed that both engineering and standard network cables experienced an increase of over 2dB in the worst-case insertion loss margin. This was due to the decrease in resistivity with temperature, which reduced the DC loop resistance and thus the insertion loss.

The worst-case return loss margin also changed by approximately 1dB. This was because the temperature decrease was not uniform across the cable, causing varying degrees of material contraction and exacerbating impedance imbalance, leading to changes in return loss.

The worst-case values for equivalent far-end crosstalk ratio and integrated equivalent far-end crosstalk ratio both increased by 1dB, related to the decrease in insertion loss, which improved signal integrity. The twisted-pair structure did not change significantly at low temperatures, so noise levels remained stable, leading to increased equivalent far-end crosstalk ratios. However, the attenuation-to-crosstalk ratio remained unchanged, as it is the ratio of signal to near-end crosstalk, which remained stable according to the test report.

After the -20℃ test, we proceeded to test the cables at 60℃.

Using professional Fluke cable testing equipment in this environment, we simulated the acceptance testing of cables at 60℃. The test results showed that neither type of cable passed the Fluke permanent link test.

From the test results, we observed that while neither cable passed, their transmission performance parameters differed. We then conducted a quantitative analysis of these parameters.

The test results showed that both engineering and standard network cables experienced a decrease of about 2.8dB in the worst-case insertion loss margin. This was due to the increase in resistivity with temperature, increasing the DC loop resistance and thus the insertion loss.

The worst-case return loss margin also decreased by approximately 1dB.

The worst-case values for equivalent far-end crosstalk ratio and integrated equivalent far-end crosstalk ratio both increased by 1dB, related to the increase in insertion loss, which attenuated both signal and noise. However, noise levels, being lower, were more affected by the insertion loss, resulting in increased equivalent far-end crosstalk ratios. The attenuation-to-crosstalk ratio remained unchanged, as it is the ratio of signal to near-end crosstalk, which remained stable according to the test report.

The high and low-temperature test results for Cat 6 cables were similar to those of Cat 5e cables. Due to space limitations, the parameter analysis for Cat 6 cables will be conducted later.

From the test results, we conclude that commonly used cables on the market perform better at -20℃ than at 20℃. However, when using cables, it is not only the transmission performance that needs attention but also the physical properties of the cable materials, such as the lifespan of PE/PVC. Low temperatures can damage the lifespan of these materials. At 60℃, the transmission performance of the cables is worse than at 20℃, and high temperatures can also damage the lifespan of these materials.

Therefore, when the cable usage environment has extreme temperatures, it is recommended that users communicate with manufacturers to customize solutions for the cables to adapt to the usage environment.