II. Advantages of Oil-Filled Design
Environmental Adaptability
The oil-filled structure uses petroleum jelly to block moisture, reducing the impact of humidity on signal attenuation. It is particularly suitable for harsh environments such as underground and mines.
Improved Stability
The mechanical stress buffering capability of oil-filled cables reduces signal loss caused by bending, indirectly ensuring stability over long-distance transmission.
III. Application Scenario Limitations
ADSL Service Limitations: When activating ADSL, the loop resistance must be <900Ω, and the transmission distance of 0.4mm oil-filled cables must be ≤3km.
Large-Pair Classification: Oil-filled cables are commonly found in large-pair specifications such as 50-pair and 100-pair cables, and are primarily used for voice backbones or mine communications.
In summary, the oil-filled design indirectly optimizes the effective transmission distance of multi-pair telephone cables by improving environmental adaptability and stability. However, the specific distance is still determined by the wire diameter and feed parameters.

