Raman Amplification: Understanding its Role in Optical Fibers

[eahaidar]

Hello
I understood what is the meaning of Raman scattering whether spontaneous or stimulated but I did not understand its importance in the optical fiber
The amplification role is to compensate the loss on the fiber of the signal but how did we do it in the fiber !?
Thank you

 

[Claude Bile]

Raman scattering is a scattering process with an accompanying vibrational transition, which yields a frequency shift between the incident and scattered photons (called the Raman shift).

Stimulated Raman scattering (SRS) is where Raman scattering occurs in the presence of a second incident photon. This results in two Raman-shifted photons (where ordinarily, the probability of obtaining two Raman-shifted photons from two independent photons is extremely low). Moreover, these photons are coherent. This process is analogous to stimulated emission, hence the name.

SRS can be used to amplify signals at the Raman-shifted frequency by "pumping" it with an intense field at the original, incident frequency - the same way we can amplify a signal using an EDFA.

The difference between Raman amplification and "ordinary" amplification is that the upper Raman state is a short-lived virtual state.

Claude.

 

[eahaidar]

Raman scattering is a scattering process with an accompanying vibrational transition, which yields a frequency shift between the incident and scattered photons (called the Raman shift).

Stimulated Raman scattering (SRS) is where Raman scattering occurs in the presence of a second incident photon. This results in two Raman-shifted photons (where ordinarily, the probability of obtaining two Raman-shifted photons from two independent photons is extremely low). Moreover, these photons are coherent. This process is analogous to stimulated emission, hence the name.

SRS can be used to amplify signals at the Raman-shifted frequency by "pumping" it with an intense field at the original, incident frequency - the same way we can amplify a signal using an EDFA.

The difference between Raman amplification and "ordinary" amplification is that the upper Raman state is a short-lived virtual state.

Claude.

Ok I started to understand let me ask you this
Why should I care if the phonon is acoustic or optic it is only different in the frequency??