What is the Difference Between Loose Tube and Tight Buffered Cables?

Fiber optic cables are the lifeblood of any fiber optic network, serving as the primary link between network transceivers and passive networking hardware. Like the veins that carry blood to various organs in the body, fiber optic cables carry light signals between multiple types of hardware. In short, they form the fundamental building blocks of any ICT network.

So, choosing the cable to use when running your network is critical to its quality and success.

An important consideration when selecting cables is which cable construction is best for the environment in which your network will operate. Some cables are better suited indoors than outdoors and for wet environments rather than dry ones.

When selecting the cable, there are several factors to consider. However, there are generally two main options when considering cable construction: tight buffered fiber optic cable and loose tube buffered cable. Other cable construction types, such as microcore, microtube, ribbon, flexible ribbon, and hybrid cable types, also offer additional advantages and benefits. This article will focus on the 2 main cable types in use – tight buffered fiber optic cables and loose tube fiber optic cables.

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Tight Buffered Fiber Cables

Tight buffered cables typically consist of the 900μm buffered optical fiber surrounded by an aramid yarn or E-glass strength member in a halogen-free outer sheath. They can be used both indoors and outdoors and are designed so that the buffer material is in direct contact with the fiber. This construction protects individual fibers during handling, routing, and connection.

Tight buffer cables, also known as riser or fiber optic distribution cables, are mainly used in buildings and campuses, usually installed in cable trays or ducts. They are, therefore, suitable for use in internal plants or building networks. These cables have generally the LSZH sheath.

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There are two main types of tight-buffered cable structures, branch cable structures (also known as fan-out cables) and distributed structures. Distribution cables are designed to be more compact than distribution structures, but the tight-buffered fibers inside the cable are only bundled in a single outer jacket for protection.

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In branch cables, each single-core cable has its own aramid yarn strength member and sheath. These subunits are wrapped in polyester tape and wrapped in LSZH. This means the cable can be split into simplex cables for separate use. Branch cables are designed for installations requiring a reliable design where protection from other machinery and the environment is required. These cables are the easiest to install and are used to terminate the connector directly to the subunit and connect directly to the panel.

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Loose Tube Buffered Cables

Loose tube fiber optic cable, typically consisting of 250-micron cores, mounted in bundles within a tube. A single tube may contain 12 individual fiber cores. These 12 fiber tubes can then be bundled with the other 12 fiber tubes to form a multi-fiber single cable, e.g., 12 x 12 fiber tubes = 144 fibers loose tube cable. The loose-tube fiber optic cable typically houses 432 fibers within these tubes. Loose tube cables are manufactured in dry blocks or gel-filled form.

This example of a multi-loose tube cable contains up to 144 250μm fibers in 12 fiber gel-filled loose tubes. The tubular design allows groups of fibers to be dropped at different points without interfering with other tubes being routed to different locations. This type of cable also usually includes a central strength member to provide more robustness to the cable.

Additionally, the type of outer sheath and material used is also suitable for exterior or outdoor plant use. It offers waterproof tape, rodent protection (such as steel wire armor), termite protection, sacrificial sheathing, and many other potential advantages when used outdoors or in harsh environments, usually, most outdoor cables use the PE nylon outer jacket.

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Loose tube cables are better for outdoors and harsh environments because they hold the fiber inside a gel that protects the fiber from water and temperature changes. These cables should not be routed through multiple corners or bends, as this can damage the gel and expose the core. Due to the diameter of the optical fibers used in loose-buffer cables, they typically hold more fibers than tight-buffer cables.

Tight-buffered cables, on the other hand, are great for indoor use and medium-length LAN/WAN connections because they're a more robust option. Another advantage of tight-buffered cables is that they are easier to install as there is no gel to clean up afterward. They do not require a fan-out kit for splicing or termination, as you can crimp the connector directly onto each fiber.

Therefore, the application and environment in which the cable will be used will determine the best selection.

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Conclusion

Loose tube fiber optic cable provides stable and highly reliable optical transmission performance in a wide temperature range, provides optimal optical fiber protection under high tension, and can be easily moisture-proof with water-blocking gel. Tight-buffered cables offer high reliability, versatility, and flexibility in a smaller footprint for easy installation. HOLIGHT supplies all Loose Tube and Tight Buffered Cable products and solutions to the global market, please always feel free to contact us for further questions!