The material selection of the armor layer of indoor bundled spiral armored cable is the basis for protecting the internal optical fiber from extrusion. This type of armor layer is mostly made of high-strength metal strips or alloy materials. These materials themselves have high compressive strength and can maintain their own shape when subjected to external extrusion and are not easy to deform. When the indoor bundled spiral armored cable is stepped on, pressed by heavy objects, or squeezed by other external forces, the armor layer will first bear these pressures, using its own hardness and toughness to resist deformation, prevent the pressure from being directly transmitted to the fragile optical fiber inside, and provide the first solid protective barrier for the optical fiber.
The spiral winding structure of the armor layer plays a key role in anti-extrusion. This spiral design allows the armor layer to form an elastic structure similar to a spring. When subjected to radial extrusion, the gap between the spirals will shrink appropriately, absorb part of the pressure through deformation, and disperse the concentrated extrusion force to a larger area. For example, when a certain point is squeezed, the spiral structure will transfer the force to the adjacent several turns of the armor layer to prevent a single part from being subjected to excessive pressure, thereby reducing the local pressure on the internal optical fiber and reducing the risk of the optical fiber breaking due to excessive local force.
The buffer layer between the armor layer and the internal optical fiber further enhances the anti-extrusion effect. The buffer layer is usually made of soft polymer material, tightly wrapped around the outside of the optical fiber, and in contact with the inner wall of the armor layer. When the armor layer is squeezed and slightly deformed, the buffer layer will absorb the residual pressure like a sponge, reducing the force transmitted to the optical fiber; at the same time, the buffer layer can fill the gap between the armor layer and the optical fiber to prevent the optical fiber from shaking and colliding due to squeezing inside, ensuring that the optical fiber is always in a relatively stable state and is not disturbed by external force impact.
The thickness and density design of the armor layer are optimized according to the possible squeezing intensity. In the parts of the indoor bundled spiral armored cable that are prone to frequent squeezing (such as corners and ground wiring), the armor layer will use thicker materials or denser spiral winding density to enhance the compression resistance; in relatively safe areas, the armor layer maintains a moderate thickness to ensure protection while preventing the indoor bundled spiral armored cable from being too bulky. This differentiated design allows the armor layer to focus on protection at key locations and comprehensively respond to squeezing risks in different scenarios.
The synergy between the armor layer and the outer sheath of the indoor bundled spiral armored cable improves the overall anti-extrusion performance. The outer sheath usually has a certain degree of elasticity and wear resistance. It is wrapped around the outside of the armor layer. When it is squeezed, the outer sheath will deform first, absorb part of the impact force, and reduce the pressure transmitted to the armor layer; at the same time, the outer sheath can protect the armor layer from erosion by the external environment (such as moisture, chemicals), maintain the structural stability of the armor layer, ensure that it maintains good compressive performance for a long time, and allow the armor layer to continue to provide anti-extrusion protection for the optical fiber during long-term use.
The armor layer's anti-deformation recovery ability can maintain continuous protection for the optical fiber after the extrusion is released. After the high-quality armor material is slightly deformed by extrusion, it can partially return to its original state when the pressure disappears, avoiding gaps or dislocations between the armor layer and the optical fiber due to long-term deformation. This recovery ability ensures that the armor layer always tightly wraps the internal structure. Even after multiple extrusions, it can maintain its original protective shape and will not reduce the protective effect on the optical fiber due to accumulated deformation, thus ensuring the stability of the indoor bundled spiral armored cable in long-term use.
In addition, the details of the edge processing of the armor layer can also reduce the potential damage to the optical fiber during extrusion. The edges of the armor layer are smoothed to avoid sharp edges. When the indoor bundled spiral armored cable is extruded and bent, the smooth edges will not scratch the internal buffer layer and optical fiber; at the same time, the end of the spiral winding is firmly fixed to prevent looseness or warping during extrusion, ensuring that the armor layer forms a complete closed structure, wrapping the optical fiber in all directions, leaving no blind spots for protection, so that the internal optical fiber can be reliably protected under various extrusion conditions.
