Unidirectional Ring-Based WDM Fiber Network for Both Downlink and Uplink Signal Access

In the paper, a dual-bidirectional ring-type wavelength-division-multiplexing (WDM) access network with downlink and uplink signal access simultaneously using a single fiber backbone in clockwise and counterclockwise directions, respectively. The proposed network architecture is simple and easy to implement via the designed remote node (RN) and optical line termination (OLT) modules, but it also can double the downlink traffic using the original WDM downlink wavelengths. The presented ring-type WDM network can also avoid the Rayleigh backscattering (RB) beat noise when the same wavelengths are applied as downlink and uplink channels concurrently. In the measurement, 50 km long-reach and 15 km short-reach fiber transmission lengths are achieved for the symmetrical 10 and 28 Gbit/s on-off keying (OOK) data access, respectively. In addition, based on the obtained power budgets of eight downlink WDM signals and network design at the forward error correction (FEC) threshold, 16 optical network units (ONUs) can be supported simultaneously.