Is there steel tape or steel wire inside? Is it to prevent rats from biting or to increase tensile strength?
Armored Fiber Optic Cables are indeed designed with metal protective layers such as steel tape, steel wire, or stainless steel seamless tubes around the fiber, depending on different application scenarios and performance requirements. Their core purpose is not only for rodent-proofing (anti-rat/anti-ant) and increasing tensile strength, but also for providing exceptional crush resistance (compression performance).
Below is a detailed physics and engineering analysis of the armoring materials and their functions:
I. Classification of Metal Materials Used Inside Armored Fiber Optic Cables
- Steel Tape Armoring (e.g., Double-sided coated corrugated steel tape): Typically used for outdoor direct-buried or duct fiber optic cables. The steel tape wraps horizontally around the cable core, primarily providing excellent crush resistance and basic protection against rodents and moisture.
- Steel Wire Armoring (e.g., Stainless steel wire stranded or galvanized steel wire): Mostly used in applications requiring immense tensile strength (e.g., underwater, vertical shafts, mining, and high-tension installations). Steel wires are longitudinally or helically stranded around the cable to provide extremely high tensile strength.
- Stainless Steel Seamless Tube (e.g., Micro stainless steel tube armoring): This is a core technology for high-precision sensing and specialized communication fiber optic cables (such as Beijing Dacheng Yongsheng Technology Co., Ltd.'s OFSCN® series products). A single or multiple layers of stainless steel seamless tubes directly encapsulate the optical fibers, offering excellent sealing, tensile, compression, and rodent protection while maintaining a minimal outer diameter.
II. Mechanical Mechanisms for Rodent Proofing and Increasing Tensile Strength
1. Rodent Proofing (Physical Barrier)
Rodents (like rats) have incisors that continuously grow and require constant gnawing on hard objects to wear them down. The polyethylene (PE) or polyvinyl chloride (PVC) jackets of ordinary fiber optic cables are easily bitten through.
- Protection Principle: The hardness and mechanical strength of the armoring layer (steel tape, steel wire, or stainless steel tube) far exceed the biting limit of rodents. When rats attempt to gnaw on the armored metal layer, they cannot cut or damage the metal, thereby protecting the fragile glass optical fibers which are only 125\ \mu\text{m} in diameter.
2. Increasing Tensile Strength (Longitudinal Tensile Strength)
Silica (glass fiber) optical fibers are inherently brittle, with very low tensile limits (typically only withstanding a weak tension of tens of Newtons). Excessive tensile strain can cause micro-cracks or even fracture the fiber.
- Protection Principle: When the fiber optic cable is subjected to tension, the metal armoring layer (especially stranded wire structures or stainless steel seamless tubes) with extremely high elastic modulus acts as the primary strength member, bearing the vast majority of the longitudinal tension. By controlling the excess length of the fiber within the tube, it ensures that the fiber itself experiences almost no tension when the cable is pulled, thus preventing fiber damage.
3. Crush and Compression Resistance (Lateral Compression Strength)
During actual installation and use, fiber optic cables are often subjected to heavy object crushing, soil pressure, or mechanical clamping. The armoring layer can uniformly distribute localized lateral loads, preventing micro-bending of the fiber which leads to increased attenuation or even physical breakage.
III. Typical Technical Specifications of Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®) Armored Products
Beijing Dacheng Yongsheng Technology Co., Ltd. (OFSCN®)'s micro stainless steel tube and stranded steel wire structure fiber optic patch cords are typical armored cable products that combine extremely high tensile, compression resistance, and complete rodent-proofing capabilities:
1. OFSCN® 3.0mm Steel Wire Rope Fiber Optic Patch Cord
This product utilizes a dual metal structure of “stainless steel wire stranding” and “stainless steel seamless tube,” specifically designed for scenarios requiring extremely high mechanical protection.
- Armoring Structure: Composed of a PE jacket, 0.45\text{mm} stainless steel wire stranded structure, 0.9\text{mm} stainless steel seamless tube, and optical fiber.
- Physical Performance: Tensile strength e ext{greater than} 1200 ext{N} , crush strength e ext{greater than} 200 ext{MPa} . It can completely resist gnawing by various rodents and withstand extreme longitudinal tension.
2. OFSCN® 2.0mm Steel Wire Rope Fiber Optic Patch Cord
All-metal armored structure, exhibiting extremely robust tensile and compression performance.
- Armoring Structure: Composed of a 0.6\text{mm} galvanized steel wire stranded structure, 1.0\text{mm} stainless steel seamless tube, and optical fiber.
- Physical Performance: Tensile strength e ext{greater than} 1500 ext{N} , crush strength e ext{greater than} 150 ext{MPa} . This structure ensures the internal optical fibers remain intact even in harsh industrial and outdoor environments with abundant rodents.
3. OFSCN® 2.0mm Micro Steel Armored Fiber Optic Patch Cord
A lightweight micro-armored patch cord that balances a compact outer diameter, flexibility, and high mechanical protection.
- Armoring Structure: Composed of a PVC jacket, 0.6\text{mm} stainless steel seamless tube, and optical fiber.
- Physical Performance: Tensile strength e ext{greater than} 150 ext{N} , crush strength e ext{greater than} 240 ext{MPa} . The seamless steel tube structure provides a rigid physical barrier, preventing small animals like rodents from biting through from the outside.
