Fibre 101 - October 08, 2020
Fibre optic cables are the lifeline of any fibre optic network and act as the main link between network transceivers, and passive network hardware. Just like veins that carry blood to various organs within a human body, fibre optic cables carry light signals between various types hardware. Simply put, they form part of the essential building blocks of any ICT network.
Therefore, this means selecting which cables you want to use when running your network is essential to its quality and success. Warren & Brown Networks stock a large variety of cables to suit any budget and requirement. Our product line includes a variety of singlemode, multimode, OM1, OM2, OM3 and OM4 options, to name a few.
An important thing to consider when selecting your cables is which cable structure is best suited for the environment in which your network will operate. Some cables are better suited to indoor as opposed to outdoor, and wet conditions as opposed to dry.
When selecting your cables, there are multiple factors to consider, however, there are generally two main options when looking at cable construction: Tight buffered fibre cables and loose tube buffered cables. Other cable construction types such as micro core, mini tube, ribbon and flexible/rollable ribbon, as well as hybrid cable types are also available and provide other advantages and benefits. This article will focus on 2 main cable types being used – tight buffered fibre optic cables and loose tube fibre optic cables.
1. Tight Buffered Fibre Cables
Tight buffered fibre cables are generally constructed with 900μm buffered fibres surrounded by aramid yarn or e-glass strength members jacketed in an LSZH outer jacket. They can be used both indoors and outdoors and are designed in such a way that the buffering material is in direct contact with the fibre. This structure protects individual fibres during the handling, routing and connecting process.
The main use of tight buffered cables, also known as riser cable or fibre distribution cable, is within buildings and campuses, and are generally installed on cable trays or in conduits. Therefore, they are suitable for internal plant or building networks.
These cables are generally supplied with a LSZH sheath.
There are two main types of tight buffered cable structures, breakout cable structure (also known as fan-out cables) and distribution structure. The distribution cable design is more compact than the breakout structure, however, the tight-buffered fibres inside the cable are only bundled in a single outer jacket for protection.
Within breakout cables, each simplex cable has its own aramid yarn strength member and jacket. These subunits are wrapped in a polyester tape and sheathed in LSZH. This means that the cable can be broken out into separate simplex cables for individual use. The breakout cables are designed for installations requiring a reliable design in which protection from other mechanics and the environment are required. These cables are some of the easiest to install for direct termination of connectors to sub-units and direct run to panels.
2. Loose Tube Buffered Cables
Loose tube optical fibre cables, consist generally of 250 micron fibre core, installed in bundles within a tube. A single tube may consist of 12 individual fibre cores. Each of these 12 fibre tubes may then be bundled with other 12 fibre tubes, to make up a single cable of multiple fibre cores, e.g 12 x 12 fibre tubes = 144 fibre loose tube cable.
This example of a multi loose tube cable, would consists of up to 144, 250μm optical fibres in 12 fibre gel-filled loose tubes. The tube design allows groups of fibres to be dropped-off at different points without interfering with other tubes being routed to separate locations. This cable also generally contains a central strength member to provide more sturdiness to the cable.
Furthermore, the outer sheath and type of material used also provides suitability for external or outside plant use. It features water blocking tape, rodent proofing (e.g. steel wire armour), termite resistance, sacrificial sheaths and many other potential benefits when used in outside or harsh environments.
For Australian conditions, most cables use a PE Nylon over sheath.
Loose Tube vs Tight Buffered
Loose tube cables are better suited for outdoor and harsh environments as they secure the fibres within a gel that protects the fibres from water and temperature changes. These types of cables should not be routed through multiple corners or bends as this causes damage to the gel and will result in the core being exposed. Due to the diameter of the of the fibres used in loose tube cables, they generally hold more fibres than tight buffered cables.
On the other hand, tight buffered cables are perfect for indoor use and medium length LAN/WAN connections as they are the sturdier option. Another advantage to tight buffered cables is that they are much easier to install as there is no gel to clean up afterwards and they do not require a fan out-kit for splicing or termination as you can crimp connectors directly to each fibre.
Therefore, it is the application and environment in which the cable is being used, that will determine the best cable of choice to use.
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