Fiber Optic Cable :: Characteristics

Performance Parameters

Three key performance parameters for single-mode fibers are:

1. Attenuation
2. Dispersion
3. Mode-Field Diameter

It is important to know that these performance parameters can vary significantly among fibers by different manufacturers. Before making a decision, please find out the best fiber that will not lead to system malfunction and offer the best performance for your system's needs.

Attenuation

Attenuation is the loss or reduction in signal strength over a certain distance. In the case of optical fiber, this is measured in decibels per kilometer (dB/km). When first developed, optical fiber handled attenuation of less than 20 dB per km. Now, typical attenuation is 0.35 dB per km at a wavelength of 1310 nanometers (nm) and even lower at 1550 km (0.25 dB per km).

Several factors lead to increased attenuation, primarily scattering and dispersion. Molecular irregularities in the glass cause the light to scatter. Further attenuation is caused by light being absorbed by residual materials, such as metal and water ions. It is recommended to buy a fiber cable that has a low water loss to try to prevent as much attenuation as possible.

Dispersion

In optics, dispersion is a phenomenon that causes the separation of a wave into spectral components with different frequencies, due to a dependence of the wave's speed on its frequency. During the process of digital transmission, dispersion can limit the maximum data rate, maximum distance, or the information-carrying capacity of the single-mode fiber. With analog transmission, dispersion can create unacceptable levels of composite second-order distortion (CSO).

Mode-Field Diameter

This describes the size of the light-carrying part of fiber, including the core and a small part of the cladding glass for single-mode fibers. Mode-field diameter (MFD) is important to note because it is a performance parameter that can determine the effect of bend-induced loss as well as splice loss. Rather than being only the core diameter, MFD is a function of wavelength, the aforementioned core diameter, and the refractive-index

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