Shipboard optical cables are specifically designed for the marine environment, providing stable and reliable data transmission. They are not only used for internal ship communication but are also widely applied in transoceanic communication and data transmission for offshore oil and gas platforms. In modern marine communication systems, shipboard optical cables play a crucial role. To ensure the stability of marine operations, the design of shipboard optical cables requires them to be waterproof, pressure-resistant, corrosion-resistant, and to have sufficient mechanical strength as well as good bending performance.
Generally, the structure of shipboard optical cables should at least include fiber units, tubes, armor layers, and jackets. Shipboard optical cables designed for special purposes or applications may not have an armor layer but may use more wear-resistant materials or special outer jackets. Additionally, to cope with different environments, shipboard optical cables may also have structures such as fire-resistant layers, central/auxiliary reinforcement members, and additional water-blocking elements.
Next, we will introduce the structure of shipboard optical cables and the materials used in each part.
1.Fiber unit
The fiber unit is the core part of shipboard optical cables, containing one or more optical fibers. Optical fibers are the central component of the cable, typically composed of a core, cladding, and coating layer, structured as concentric circles. The core, located at the center, is made of high-purity silica and is responsible for transmitting the optical signal. The cladding, also made of high-purity silica, surrounds the core and provides a reflective surface for light transmission, optical isolation, and a certain degree of mechanical protection. The coating layer, the outermost part of the fiber, is composed of materials such as acrylate, silicone rubber, and nylon, protecting the fiber from moisture and mechanical abrasion.
Optical fibers are generally divided into single-mode fibers (such as G.655, G.652D) and multi-mode fibers (such as OM1-OM4), with different types having varying transmission characteristics. The transmission characteristics of fibers include maximum attenuation, minimum bandwidth, effective refractive index, numerical aperture, and maximum dispersion coefficient, which determine the transmission efficiency and distance of the fiber.
Fibers are typically surrounded by loose or tight tubes to reduce interference between fibers and the impact of the external environment. The design of the fiber unit ensures the efficient data transmission capability of the optical cable and is the most fundamental and critical part of shipboard optical cables.
2.Tube
The fiber tube is a key component of the optical cable used to protect the optical fibers. It can be divided into tight-buffered tubes and loose tubes based on its structure.
Tight-buffered tubes are typically made from materials such as polypropylene resin, polyvinyl chloride, or halogen-free flame-retardant polyethylene. These tubes fit closely around the fiber surface with no significant gaps, providing minimal movement space for the fiber. This tight coverage offers direct protection to the fiber, helping to prevent moisture ingress and providing high mechanical strength and resistance to external interference.
Loose tubes, on the other hand, are usually made from high-modulus PBT plastic and are filled with grease to block water and provide cushioning protection. Loose tubes have good flexibility and resistance to lateral pressure. The design with grease and other water-blocking compounds not only allows the fiber to move freely within the tube, facilitating fiber extraction and maintenance, but also provides additional protection to prevent fiber damage. It can also prevent moisture ingress, protecting the fiber from damage and ensuring the stability and safety of the optical cable in humid or underwater environments.
3.Armor layer
The armor layer is located inside the outer jacket, and its primary function is to provide additional mechanical protection to prevent the shipboard optical cable from physical damage. The armor layer is typically a galvanized steel wire braid (GSWB). The galvanized steel wires are woven to cover the cable, with a coverage rate of no less than 80%. The armor structure provides extremely high mechanical protection and tensile strength, and the woven coverage makes the armored cable relatively flexible. It offers additional mechanical strength while maintaining a small bending radius (the dynamic allowable bending radius for shipboard optical cables is 20D), making it suitable for applications that require frequent movement or bending. Additionally, due to the inherent properties of the galvanized steel wire material, the addition of the armor layer also provides additional corrosion resistance, making it suitable for use in humid or salt fog environments.
4.Jacket
The jacket is the direct protective layer of shipboard optical cables, designed to withstand exposure to sunlight, rain, seawater corrosion, biological damage, physical impact, and ultraviolet radiation. The jacket is typically made from environmentally resistant materials such as polyvinyl chloride (PVC) or low-smoke zero-halogen polyolefin materials (LSZH), which provide excellent resistance to ultraviolet light, weathering, chemical erosion, and flame retardancy. These properties ensure that the optical cable remains stable and reliable even under the harsh conditions of the marine environment. For safety reasons, the outer jackets of current shipboard optical cables are almost exclusively made from low-smoke zero-halogen flame-retardant polyolefins, such as LSZH-SHF1, LSZH-SHF2, and LSZH-SHF2 MUD. LSZH materials produce very low smoke density when burned and do not contain halogens (such as fluorine, chlorine, bromine), thus avoiding the release of large amounts of toxic gases. The most common material used is LSZH-SHF1.
5.Fire-resistant layer
In certain critical areas, to ensure the continuity and reliability of the communication system for firefighting purposes such as alarms, lighting, and communications, some shipboard optical cables are designed to include a fire-resistant layer. Loose tube structured optical cables typically require the addition of mica tape to enhance their fire-resistant performance. Fire-resistant cables can maintain communication capabilities for a certain period during a fire, which is crucial for the safety of the vessel.
6.Strengthening member
To enhance the mechanical strength of shipboard optical cables, central strengthening members such as phosphated steel wires or fiber-reinforced plastic (FRP) are added internally. These components increase the strength and tensile capacity of the cable, ensuring its stability during installation and use. Additionally, auxiliary strengthening members like aramid yarn can be incorporated to further improve the strength and chemical resistance of the shipboard optical cables.
7.Structural improvement
With the advancement of technology, the structure and materials of shipboard optical cables are also continuously being updated. For example, all-dry loose tube optical cables have abandoned the traditional grease-filled water-blocking method, using dry water-blocking materials in both the loose tubes and the cable core, offering advantages such as environmental friendliness, light weight, and grease-free. Another example is the use of thermoplastic polyurethane elastomer (TPU) as the jacket material for optical cables. This material has a wider operating temperature range and is resistant to oil, acids, and alkalis. It is also lightweight and takes up less space. These examples show that the design of shipboard optical cables is still being constantly improved.
8.Summary
The structural design of shipboard optical cables takes into account the special requirements of the marine environment, including water resistance, pressure resistance, corrosion resistance, and mechanical strength, among others. The high performance and reliability of shipboard optical cables make them an indispensable part of modern marine communication. With the advancement of marine technology, the structure and materials of shipboard optical cables are also continuously improving to meet the needs of deeper marine exploration and more complex communication requirements.
Post time: Jan-13-2025