Forward pumping provides the highest SNR, and the smallest noise figure, because most of the Raman gain is then concentrated toward the input end of the fiber where power levels are high. However, backward pumping is often employed in practice because of other considerations such as the transfer of pump noise to signal and the effects of residual fiber birefringence. 

Sanjay Yadav

Optical Communications & Network Automation Expert | Author of 3 Books for Optical Engineers | Founder, MapYourTech

Optical networking engineer with nearly two decades of experience across DWDM, OTN, coherent optics, submarine systems, and cloud infrastructure. Founder of MapYourTech. Read full bio →

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