Optical Amplifier for DWDM systems

Recommendation1-Raman amplifier is better because it provides distributed amplification within the fiber. Now what is distributed amplification?

 

Distributed amplification uses the transmission fiber as the gain medium by multiplexing a pump wavelength and signal wavelength. Now what is the advantage of this?

 

It increases the length of spans between  the amplifiers and regeneration sites. So this provides amplification over wider and different regions.

 

This is the major advantage of Raman over EDFA.

 

Recommendation 2-If Raman amplifier is better than EDFA then why does most of the network design still utilize EDFAs? Is it because of the high pump power required in case of Raman?

 

EDFA Advantages: 

-consistent with the low attenuation window 

-high energy conversion efficiency 

-high gain with little cross-talk 

-good gain stability 

 

EDFA Disadvantages: 

-fixed gain range 

-gain up-flatness 

-optical surge problem 

 

RFA Advantages: 

-flexible gain wavelength 

-simple structure 

-nonlinear effect can be reduced 

-low noise 

 

RFA Disadvantages: 

-high pump power, low efficiency, high cost 

-components and fiber undertake the high power

 

Recommendation 3-Both have advantages and disadvantages as well explained above, but do you need EDFA, Raman or both in your network? 

 

It strictly depends on the characteristics of the fiber link you need to deploy (length, fiber type, attenuation, CD, PMD, EOL channel count, etc.) so you may not need Raman if EDFA can do the job: this is something that a network designer must verify when he plans a DWDM network... and also cost of hw is something very important in planning.