Choosing correct fiber optic cable and installation issues

When designing optical fiber network choosing correct fiber optic cable is critical for success of the project.

 

First, it is important to match ratings between equipment and cabling. In other, words choose 800 nm cable if using 800 nm equipment. It is especially important to check correct cables, in case you plan to use sophisticated DWDM muxes, some cheaper optical cables might have big attenuation at wavelength windows you will need.

 

The locale of the cable is also very important. Inside cable would perform poorly when installed outside, since it is lacking the protection features necessary, for outside use. Important to remember safety of personnel – un-terminated cable should not be touched with bare hands because of the danger of glass slivers, and should not be looked at directly – it could harm human vision。

 

In order to avoid any unnecessary danger for people, fiber-optic cable is typically terminated in some kind of enclosure.

 

One of the options for enclosure is patch panel. It gets multiple fiber-optic cables as input and allows interconnect them inside enclosure with short interconnect cables. Another option for optical enclosure is the fiber distribution panel.

 

It allows interconnections the same way as fiber patch panel. The difference is in connectors – they are more permanent. It is commonly used for splitting multi-fiber cables into individual cables.

 

There are several important factors affecting the performance and might decrease quality of the signal. First of them is attenuation or loss of data carrying  signal power. Attenuation is measured in dBs. More dBs represent higher signal loss (3dB equals 50% signal power loss). Cables with high attenuation specification are having shorter maximum transmittance distances. Things like dirty fiber end faces, imperfection of fiber, excessive bending, poor installation, and excessive stretching affect attenuation directly.

 

Another factor affecting performance is the acceptance angle – an angle at which laser could transmit signal through fiber successfully. Greater acceptance angle between two or more signals in multimode fiber result in negative performance of cable.

 

Characteristics like Numerical Aperture, Modal Dispersion and Bandwidth, and Chromatic Dispersion result from acceptance angle and affect overall performance. They are related to refractive specifications of the core, transmission delays and fiber bandwidth, and wavelength distribution respectively.

 

Specifically, for FTTx networks, choosing a cable is important, since you will usualy need transmit 3 wavelengths, like 1310/1490/1550 nm and if you are interested to read more, here are some guidelines specifically for FTTx.