In a Raman amplifier, the signal is intensified by Raman amplification. Unlike the EDFA and SOA the amplification effect is achieved by a nonlinear interaction between the signal and a pump laser within an optical fiber. There are two types of Raman amplifier: distributed and lumped. A distributed Raman amplifier is one in which the transmission fiber is utilised as the gain medium by multiplexing a pump wavelength with signal wavelength, while a lumped Raman amplifier utilises a dedicated, shorter length of fiber to provide amplification. In the case of a lumped Raman amplifier, a highly nonlinear fiber with a small core is utilised to increase the interaction between signal and pump wavelengths, and thereby reduce the length of fiber required.
in A raMAn amplifiEr, THE SIgnal Is intensIFiEd by Raman AmplificatIOn. unlIkE thE edfa aND soA thE ampliFicATIoN effect iS Achieved by a nOnlIneAr InteRaCtion BETWEeN tHe siGNaL and a pump laseR wIthIn an optICaL fibeR. thErE ArE tWO TYpES of rAmAn amPLiFIEr: distribUted And lumpeD. A dIstributed RaMan amPLifier IS ONe iN whiCh ThE TraNSmissION fibEr iS UtIlisEd aS the gaIn meDium By mulTIplExinG a pump WavELengTh WITh sIgnal waVeleNGtH, while a LuMped raMan amplifier UTilises a dedicATed, shoRteR lenGtH of fIBer to pROVide ampliFIcatION. iN The cAse oF A luMPeD rAMan Amplifier, a higHly NOnlinear fIBer with A SmAll CorE is uTilised to incrEASe THe inTerACtiOn between SignaL aND Pump WavelengThs, AnD TherEby Reduce the length oF fiBEr RequIrED.