Classification of optical cables by laying purpose

Optical cables are classified by laying method into indoor, outdoor, aerial, direct-buried, pipeline, and submarine types, each designed for specific installation environments and mechanical requirements.

Indoor Optical Cables

Indoor optical cables are primarily used for horizontal subsystems and vertical backbone subsystems within buildings. Horizontal cables are similar to twisted pair cables but require careful handling due to lower tensile strength and larger bending radii. Vertical backbone cables connect equipment rooms to distribution rooms on each floor and are typically installed in cable shafts or risers. Proper fixing with nylon ties or steel clips, sealing of pipe holes, and fireproofing measures are essential to ensure safety and durability. Cable reserves of 5–10 meters are usually left at equipment ends for flexibility during installation .

Outdoor Optical Cables

Outdoor optical cables are designed for long-distance trunk lines, local telephone relays, LANs, private networks, and underwater communications. The main laying methods include:

• Aerial Optical Cables: Installed on utility poles, either using a suspension wire (cable hangs on a supporting wire) or self-supporting type (cable carries its own load). Aerial cables are cost-effective but more vulnerable to natural disasters and mechanical damage .
• Direct-Buried Optical Cables: Buried underground, requiring protection against mechanical damage and soil corrosion. Typical burial depths range from 0.8 to 1.2 meters depending on soil type, with trenching standards adjusted for ordinary soil, semi-stone, quicksand, or crossings of railways and highways. The trench bottom is padded with fine soil or sand, and the fiber strain must remain within allowable limits .
• Pipeline Optical Cables: Installed inside ducts or conduits, providing mechanical protection and easier maintenance. This method is commonly used in urban areas or where direct burial is impractical .
• Submarine Optical Cables: Laid underwater for intercontinental or regional communication. These cables are specially armored to withstand water pressure, currents, and potential mechanical impacts .

Summary of Laying Method Classification

1. Indoor cables – horizontal and vertical backbone installations inside buildings.
2. Aerial cables – suspended on poles, either with suspension wires or self-supporting.
3. Direct-buried cables – buried underground with mechanical and environmental protection.
4. Pipeline cables – installed in ducts or conduits for protection and maintenance.
5. Submarine cables – laid underwater for long-distance communication. Each type of optical cable is designed to meet the mechanical, environmental, and operational requirements of its installation method, ensuring reliable signal transmission and longevity of the network .