A distribution node of a passive optical network (PON) comprises a first port for receiving a first optical continuous envelope modulated downstream data signal at a first wavelength (λC) from a first optical line termination unit (OLT1) and a second port for receiving a second optical continuous envelope modulated downstream data signal at a second wavelength (λL) from a second optical line termination unit (OLT2). A first converter (FBG-1) performs continuous envelope modulation-to-intensity modulation conversion of the first optical downstream data signal and forwards the converted first optical downstream data signal (λC) to the first group of optical network units (ONU1 . . . N). A second converter (FBG-2) performs continuous envelope modulation-to-intensity modulation conversion of the second optical downstream data signal and forwards the converted second optical downstream data signal (λL) to the second group of optical network units (ONUN+1 . . . 2N). The distribution node forwards a seed signal at the first wavelength (λC) to the second group of optical network units (ONUN+1 . . . 2N) and forwards a seed signal at the second wavelength (λL) to the first group of optical network units (ONU1 . . . N).