Some Theory

This article gathers basic information about fiber-optic cables offered by DIPOL. The short guide is designed to help you choose the best cable for your needs resulting from the requirements for your installation.

FTTH networks make an important part of modern telecommunication installations in residential buildings and other multi-dwelling units. The growing popularity of fiber optic systems "in the last mile" is the consequence both of legislation adopted in many countries and a growing awareness of investors. Fast and reliable access to the Internet and multimedia services has become a priority. The popularization of optical fibers is also possible due to cheap and effective technological solutions. Internet service providers have noticed the advantages of passive optical networks (xPON).

The transition from copper to fiber-optic technology means the need for new tools and skills. Aside from acquiring some theoretical knowledge, installers must improve their manual skills as the work with optical fibers requires a different, more careful approach.

With the great popularity of optical links in the last few years, the main part of them is currently based on modern single-mode fibers. However, both single-mode and multimode fibers are divided into many types/categories that comply with established standards and factory specifications.

One of the basic criteria of optical equipment classification is the type of the fiber optics with which it works. It is connected with the type of transmission of light in the fiber core - single-mode or multimode. Transmission of light in optical fibers is based on the phenomenon of total internal reflection. The core, usually made of doped glass, is the center through which light travels along, while the fiber cladding is made of pure glass. Such combination of materials is dictated by their refraction indexes. To achieve total internal reflection, the refraction index of the cladding (pure glass) must be lower than the refractive index of the core (doped glass). The buffer coating surrounding the cladding is a cover layer usually made from a thermoplastic material and special gels, which protects the fiber from mechanical damage.

The most important task in the design of fiber optic link is to determine the maximum range of the optical transmission path, being in fact the balance of optical power in the link. Balance of power is a comparison of the power at the input of the optical link with the losses in fiber optic cables and other path components. This will help to find the optimal parameters of transmitting and receiving devices to ensure proper signal transmission.