Ring-based colorless WDM-PON with Rayleigh backscattering noise mitigation

We propose and experimentally demonstrate a novel ring-based wavelength-division-multiplexing passive optical network (WDM-PON). By using an orthogonal coding and correlation technique, the ring-based WDM-PON can efficiently mitigate the optical beat interference noise induced by Rayleigh backscattering. In our proposed orthogonal coding scheme, no extra light sources are required for the upstream (US) transmission, which means the number of light sources can be halved and the saved wavelengths can be used for more optical network units. In addition, compared to previous ring-based WDM-PONs, the proposed ring-based WDM-PON requires fewer fiber Bragg gratings and no blue/red-band filter, which means the proposed orthogonal coding scheme costs less. The performance of the proposed scheme is investigated through an experiment. In the experiment, 2.5 and 5 Gb/s US data rate and 5 Gb/s downstream data rate are investigated in two different ring architectures. According to the experimental results under different situations, it can be concluded that the US orthogonal coding scheme performs better than the normal US on–off keying in a ring-based WDM-PON. The power margin can be up to 1.8 dB when the US data rate is 2.5 Gb/s, and the power margin can be up to 1.69 dB when the US data rate is 5 Gb/s.