Simple Optical Fiber Calculations

Introduction

Here i will try to describe about the simple Optical Fiber calculations done in the field.

Attenuation:
1) For an SMF fiber with attenuation coefficient 0.25 dB/Km, what is the attenuation for 100 Kms of SMF fiber?

attenuation coefficient= 0.25 dB/Km

length of the Fiber= 100 Km

Attenuation for 100 Km SMF fiber = Attenuation Coeffiteint x Length of the Fier
                                                          = 0.25 x 100
                                                          = 25 dB

Attenuation is usually represented in dB

Dispersion:

The Chromatic Dispersion of a fiber is expressed in ps/(nm*km), representing the differential delay, or time spreading (in ps), for a source with a spectral width of 1 nm traveling on 1 km of the fiber. It depends on the fiber type, and it limits the bit rate or the transmission distance for a good quality of service.
For a standard SMF fiber, the dispersion coeffitient is  17 ps/(nm*km)
Here also calculations can be done by direct multiplication,

ie for a 100Km standard SMF, the Residual Dispersion will be = Length of the Fiber x Dispersion Coeffitient
                                                                                                     = 100 x 17 = 1700 ps