Wavelength Re-use Scheme with Reflective SOA for WDM-PON Link

Among the various solutions to the optical subscriber network realization, the wavelength-division-multiplexed passive optical network(WDM-PON) has been considered as an ultimate next-generation solution. This article presents the wavelength re-use scheme with the reflective semiconductor optical amplifier(RSOA), which has recently been developed for application to the WDM-PON. The wavelength re-use scheme has a common feature that the optical signal modulated with downstream data is re-used to carry the upstream data through the RSOA in the subscriber-side equipment by a series of processes such as being flattened out, reflected at the rear facet of the RSOA, and then re-modulated with upstream data. The major advantage with the wavelength re-use scheme would be the possibility of realizing the simplest WDM-PON optical link structure, which is directly reflected on cost-effectiveness of the network both in equipment and maintenance costs. The gain saturation scheme is presented here; it uses the fact that the optical gain of RSOA decreases as the injection power into RSOA increases. Experimental results show that it is possible to achieve error-free bidirectional transmission with 1.25 Gbps for upstream and 2.5 Gbps for downstream data rates over 20 km transmission distance.