TWDM-PON in an ONU Amplified ODN using 170 Gbit/s DS and 40 Gbit/s US and supporting 51.5 dB loss budget

In order to achieve long fiber reach and high splitting ratio in a TDM/TWDM-PON, the optical transmitter power should be as high as possible and simultaneously the optical receiver sensitivity should be as low as possible. Of course this approach has limitations from cost and technical feasibility. Thus to achieve a very high loss budget, an in-line amplifier is typically used in the remote node (RN) as part of the optical distribution network (ODN). A drawback of this approach is that the inline amplifier needs electrical power, what might not be available at the RN location. Therefore, we propose in this paper the concept of optical network unit (ONU) amplified ODN (OAO) to achieve loss budgets much higher than possible with unamplified ODNs. We remotely control an optically powered switch from the optical line terminal (OLT) side to configure the electrical powerless RN by a low speed control channel in such a way, that one freely selectable ONU is physically point to point connected to the OLT. In our approach the ONU serves as an inline amplifier in front of the power splitter, despite it is physically located in the ONU. A configuration in which each ONU contains optical amplifiers may become a necessity in the future to enable higher bit rate TDM-PONs, because of the lack of availability of e.g. avalanche photodiodes (APD) at serial bit rates exceeding 10 Gbit/s. In our experiments the ONUs contain a reflective semiconductor optical amplifier (RSOA, very low cost one terminal amplifier) for the upstream (US) and downstream (DS) direction respectively. We demonstrate a TWDM-PON with 4 wavelengths each carrying 42.7 Gbit/s on-off-keying (OOK) in DS and 4 wavelength each carrying 10.7 Gbit/s OOK in US. The OAO solution supports a total loss budget of 51.5 dB, which is an increase of 15 dB compared to the unamplified back to back (BtB) case. In a networking experiment, we verify that the loss budget can be used to demonstrate a fiber reach of 20 km and a split ratio of 256.