What is Fiber Optic Cable Made of?


Fiber cables are used for data transmission. The basic structure of optical cable is generally composed of fiber core, strength member, filler and jacket, etc. In addition, there are waterproof coating, buffer, insulated metal wire, and other components as needed. There is no metal such as gold, silver, copper, and aluminum in the optical cable, and generally has no recycling value.


The optical fiber is mainly composed of the core, the cladding, and the coating, and the cable core is composed of optical fiber. Cable cores can be divided into single-core and multi-core. The single-core type is composed of a single fiber after secondary coating. The multi-core type is composed of multiple fibers after secondary coating, and it has two types of structures: ribbon and unit. The core is where light travels through. Fiber-optic cables transmit data via pulses of light. Light in optical fibers travels at closer to two thirds of the “speed of light” in a vacuum due to the fact that the light is traveling through glass and not through the emptiness of space.
Fiber Optic Components

  • Function: The core is the main body of the optical cable structure. Its main function is to properly position the optical fiber, so that the optical fiber can still maintain excellent transmission performance under the influence of various external forces.
  • Material: The core is made of very thin strands of glass or plastic fiber less than 1/10 the thickness of a human hair. Most fibers are made of very pure glass (silica or silicon dioxide), with very small levels of impurities to adjust the refractive index. It can carry data over longer distances with less signal loss. However, glass is more fragile than plastic and can be difficult to work with. In addition, single-mode fiber has a small core of about 9 µm, while multimode fiber has a larger core of 50 µm or above. The material of the cladding is generally silicon dioxide; and the coating can be silicon copper or acrylate.
  • Location: According to the structure of the cable core, the optical cable can be divided into four categories: stranded loose tube fiber optic cable, slotted core fiber optic cable,  ribbon fiber optic cable, and unitube fiber optic cable. The specific is shown below. 
    structure fiber cable

Strength Member

  • Function: In order to make the optical cable withstand the external force during laying and installation and avoid the optical fiber breakage, it is necessary to add some strengthening members in the center or around the optical cable.
  • Material: The strengthening member in the optical cable is generally made of galvanized steel wire, steel wire rope, stainless steel wire, and zinc-deficient steel wire with a tight-fitting polyethylene cushion. In strong electromagnetic interference environments and minefields, high-strength non-metallic materials (such as glass wool and Kevlar fibers) are used.
  • Location: The strength member is generally located in the center of the fiber optic cable, so it is also called the central strength member. The outside of the reinforcing member is usually extruded or wrapped with a layer of plastic to ensure that the surface in contact with the optical fiber is smooth and has a certain elasticity.


Jacket (Sheath)

When the optical cable has more than two jackets (layers), people often call the outermost layer the outer sheath, and the innermost layer the inner jacket.

The jacket focuses on moisture resistance, while the sheath focuses on lateral compression and abrasion resistance. In fact, it is difficult to strictly distinguish jacket and sheath. The order is generally the inner jacket, then the armor, and finally the outer sheath.

  • Function: The jacket of the optical cable mainly protects the fiber in the optical cable, avoids it from being damaged by external force, and reduces the influence of the external environment on it. It performs waterproof and moisture-proof, tensile and compressive, and bending.
  • Material: The inner jacket can be non-metallic jacket (PE jacket), aluminum-plastic bonded jacket, and steel-plastic bonded jacket. The outer sheath can be a variety of layers extruded with medium-density polyethylene or an outer sheath such as a fuel-resistant and anti-termite layer. In order to increase the tensile and lateral pressure resistance of the optical cable, the armoring layer added to the inner jacket of the optical cable is usually steel wire or steel tape.
  • Location: A layer or layers of cylindrical jacket/sheath can be added from the inside to the outside.
  • Application: The outer sheath structure of the optical cable is basically the same as that of the cable, and different sheath structures are suitable for different laying methods.
    Pipeline: Optical cables used for pipeline laying generally have a layer of aluminum polyethylene sheath. In the fiber optic cable of the filled structure, a polyethylene jacket can also be used.
    Dire buried: Commonly used outer sheaths are bonded corrugated steel sheaths, double steel tapes, or single fine round steel wire armor.
    Submarine: Fiber optic cable for subsea laying with laminated aluminum polyethylene (LAP) sheath, single fine round steel wire armor and polyethylene jacket. The optical cable used for laying in larger rivers adopts the double-layer structure of adhesive sheath and aluminum sheath, plus double thick round steel wire armor to improve mechanical strength and anti-corrosion performance.


Fiber Filling Gel

  • Material: Moisture-proof oil gel. The compound used for filling should not flow out of the cable at/under 60°C. The low-temperature bending properties of the optical cable do not deteriorate at the lowest operating temperature allowed by the light.
  • Function: Filling the gap of the optical cable core with filler gel can effectively prevent moisture and water.
  • Location: Between the cable core and the jacket.

At the End

In practical applications, in order to make the optical fiber resistant to stretching and not affected by damage, the optical fiber is generally made into different structures and other components are added to form an optical cable so that it has a certain structural strength, which can not only be used in various environments, and can ensure the stability and reliability of transmission. For example, the waterproof coating is used in the submarine optical cable, which is composed of a sealed aluminum tube, etc. The buffer is used to protect the cable core from radial pressure, and generally, nylon tape is used to wrap the wire core in an axial spiral.


Bonelinks is a fiber optic product manufacturer. We provide different types of fiber optic cable and can also be customized according to your needs. If you have any needs, please contact us, and we will provide you with the most suitable and cost-effective fiber optic cables.

Echo Huang

Echo Huang is an expert wordsmith and marketing professional at Bonelinks with more than 8 years of experience in high technology businesses – fiber optics, IoT, and telecommunication. She is very glad to share industry knowledge and communicate with others.

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