Fibre Optic Guide
Fiber-Optic Network Components
DIGITUS® Optical fiber cable
Construction of a glass fiber cable
A glass fiber cable consists mainly of three parts: The glass fiber core, carrying the light signal, the glass jacket which reflects the light and a plastic cladding which protects the glass fiber cable from external influences and makes it flexible.
The glass fiber core
There are various thicknesses of the glass fiber core which are described with their cross section: The single mode fiber cable with a cross section of 9µm and multi-mode fiber cables with cross sections of 50 µm and 62.5 µm.
Single mode fiber cables are more costly than multi-mode fiber cables because of difficulties in the manufacture of an extremely thin cable with a cross section of 9µm, but they have a greater range.
Additional designations are used to describe them in terms of their quality: OS1 and OS2 for single mode fiber cables, where OS2 is the best quality and OM1, OM2 and OM3 for multi-mode cables where OM3 is the best quality.
The difference between single mode and multi mode
The light is reflected in a zigzag pattern in the core of thicker multimode fiber cables. This results in higher attenuation, the range of the signal reduces, in other words. The light does not refract so frequently in single mode fiber cables and guarantees an enormous range.
There are several forms of cladding for glass fiber cables.
The solid strand type surrounds the fiber directly. This has a disadvantageous effect when there is high strain and with temperature differences.
Unlike the solid strand type, the hollow strand type does not surround the fiber directly. There is a hollow space between the cladding and the fiber which reduces the disadvantageous effects of strain load and temperature differences.
The combined strand type represents an intermediate form of the solid core type and the hollow core type. The hollow space of the cladding is filled here with a gel or similar.
Use of the individual glass fiber cables
Multi fire cables are usually found in cabling in buildings and in short and medium distance runs. OM2 fiber cables are used the most. OM3 fibers of better quality are used more and more frequently and replace OM2 fiber cables over the long run.Single mode fiber cables are used because of their good signal properties in long distance cabling.
The widest distributed LWL plugs are ST-, SC- and LC plugs. The LC plugs gains an ever increasing share of the market for glass fiber plugs because of the compact size and their use with mini GBIC modules in switches or media converters.
Pigtails are cables equipped with an LWL plug on one side and a plain glass fiber cable on the other side. They are used at the end points of laid cables and are spliced with each other.
Splicing is understood to be the connection of two glass fiber cables. These are adjusted at their end points and permanently fused together.