In this work, the influence of the distribution element position and the reflective optical network unit (ONU) gain in
wavelength-division-multiplexing passive optical networks are reported. After the theoretical and experimental analysis, it is
determined that the best crosstalk-to-signal ratio is achieved if the multiplexer is placed either in the ONU or optical light termination vicinity, and the ONU gain has a new optimum value depending on the position. Also, it is demonstrated that Rayleigh backscattering is generally irrelevant in downstream transmission.Peer Reviewe