Optical transmission system comprising an optical fiber link, at least one optical network element, which is an optical line terminal, OLT, for transmitting signals in a downstream direction and receiving signals in an upstream direction via said optical fiber link, and a further network element, wherein said further network element is an optical network unit, ONU, and wherein said ONU is directly connected with said OLT via said optical fiber link, wherein said optical fiber link is of the single fiber working, SFW, type, said optical line terminal comprising - transceivers (102; 102a, 102z) configured to transmit DWDM signals in the downstream direction in the optical C-band and to receive CWDM signals in the upstream direction outside the optical C-band, - primary optical pumping means configured to provide optical pump power in the downstream direction to said at least one optical fiber link, said primary optical pumping means configured to provide optical pump power to amplify the CWDM upstream signals in said at least one optical fiber link, and - secondary optical pumping means configured to provide optical pump power in the downstream direction to said further optical network element, said secondary optical pumping means configured to provide optical pump power to amplify the DWDM downstream signals in the further network element, - wherein said optical fiber link comprises optical amplification means which comprise a plurality of Raman amplifiers, wherein said primary optical pumping means (166; 266) are configured to provide optical pump power for said plurality of Raman amplifiers, and wherein Raman gain characteristics (568a,.., 568f) of said Raman amplifiers are arranged in a way to overlap each other and to overlap wavelengths (562a,.., 562n) carrying said CWDM signals, wherein said ONU comprises optical amplification means in form of an EDFA, and wherein said secondary optical pumping means are configured to provide optical pump power for said optical amplification means of said ONU, wherein said optical fiber link is connected to a port of the ONU, and wherein said EDFA of said ONU is arranged between said port and a band splitter for separating said DWDM downstream signals from said CWDM upstream signals. - transceivers (102; 102a, 102z) configured to transmit DWDM signals in the downstream direction in the optical C-band and to receive CWDM signals in the upstream direction outside the optical C-band, - primary optical pumping means configured to provide optical pump power in the downstream direction to said at least one optical fiber link, said primary optical pumping means configured to provide optical pump power to amplify the CWDM upstream signals in said at least one optical fiber link, and - secondary optical pumping means configured to provide optical pump power in the downstream direction to said further optical network element, said secondary optical pumping means configured to provide optical pump power to amplify the DWDM downstream signals in the further network element, - wherein said optical fiber link comprises optical amplification means which comprise a plurality of Raman amplifiers, wherein said primary optical pumping means (166; 266) are configured to provide optical pump power for said plurality of Raman amplifiers, and wherein Raman gain characteristics (568a,.., 568f) of said Raman amplifiers are arranged in a way to overlap each other and to overlap wavelengths (562a,.., 562n) carrying said CWDM signals, wherein said ONU comprises optical amplification means in form of an EDFA, and wherein said secondary optical pumping means are configured to provide optical pump power for said optical amplification means of said ONU, wherein said optical fiber link is connected to a port of the ONU, and wherein said EDFA of said ONU is arranged between said port and a band splitter for separating said DWDM downstream signals from said CWDM upstream signals.