Module 5 : Signal Distortion on Optical Fibers - Dispersion
Lecture 1 : Signal Distortion on Optical Fibers - Dispersion
In an optical fiber we find two types of dispersions
(1)
Intra-modal or Chromatic dispersion (present in single mode an multimode optical fiber). This dispersion is due to finite bandwidth of the signal.
The Intra-modal dispersion consists of two parts:
(a)
Material dispersion: This is due to intrinsic properties of the material, glass.
(b)
Waveguide dispersion: This is due dispersive nature of the bound medium. In a bound medium like the optical fiber, the velocity is a function of frequency.
(2)
Inter-modal dispersion (present in only multimode optical fiber). This dispersion is due to change in velocity from one mode to other.
The dispersion is a rather weak phenomenon. What that means is the pulses slowly broaden as they travel along the optical fiber.
It is therefore appropriate to investigate one type of dispersion at a time. That is when we investigate waveguide dispersion we assume the fiber material to be non dispersive, and when we investigate material dispersion, we assume the medium to be unbound.
