Module 20 : WDM Networks
Lecture      : WDM Networks
   
 
\includegraphics[width=\textwidth]{wdm24}
   
A network may allow no conversion at all in which case all the wavelengths are routed as such to the output port.
Fixed wavelength conversion: A signal entering a particular node with a wavelength $ \lambda_i$always leaves the node with a
  pre-determined wavelength $ \lambda_j$.
Limited wavelength conversion: In this case, an input wavelength $ \lambda_i$can be converted to any of a limited number of
  wavelengths. For instance, in the figure, $ \lambda_1$can be converted to either $ \lambda_1$or $ \lambda_3$but not to $ \lambda_2$. Similarly, $ \lambda-2$can be converted to $ \lambda_1$and $ \lambda_3$but cannot leave the node without conversion while $ \lambda_3$can be converted to any of the three wavelengths.
   
Full conversion: This is the case where any of the input wavelengths can be converted to any of the permitted
  wavelengths.
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