Concurrent Inter-ONU Communications for Next Generation Mobile Fronthauls based on IMDD Hybrid SSB OFDM-DFMA PONs

Abstract

In PON-based mobile fronthauls, direct inter-ONU communications without passing end-user traffic to the OLT offer a promising solution for fulfilling thethe stringent latency and bandwidth requirements of of 5G and beyond networks. In this paper, with slight modifications to at the PON remote node, a concurrent inter-ONU and upstream communication technique is proposed and experimentally demonstrated in 101.6Gbit/s multipoint-to-point hybrid SSB OFDM -digital filter multiple access (DFMA) IMDD PONs over at a distance of 25km SSMFs. Multiple gapless inter-ONU and upstream SSB signals are aggregated by digital orthogonal filtering in each ONU transmitter. A single FFT operation is applied for demultiplex and demodulation in the OLT/ONU receivers. The results show that for both the inter-ONU and upstream transmissions, the optimum length of optimal digital filters is is 32, based on which the power penalties due to the fiber transmission and ONU channel interference are <1dB and <2dB, respectively. For the inter-ONU communications, adaptive RF spectral assignments can effectively mitigate the Rayleigh and Brillouin backscattering effects and the upstream channel fading effect, thus giving rise to >30% improvements in aggregated signal transmission capacity. In addition, detailed experimental investigations are also undertaken of the trade-off between differential ONU optical launch power dynamic range and aggregated signal transmission capacity. An approximately 1dB increase in ONU launch power dynamic range is achievable by reducing the aggregated signal transmission capacity by 5Gbit/s.

Real-Time Demonstration of Concurrent Upstream and Inter-ONU Communications in Hybrid OFDM DFMA PONs

“…However, the RF signal bandwidth employed in the current set up is only 1 GHz. Therefore, the Stokes and anti-Stokes components do not generate any undesired signal components, as shown in [9].…”

“…The small penalty due to the RN modification could be attributed to the Rayleigh backscatteringinduced optical signal, since the associated fiber length is only 2 km, this explains the small penalty. To further study the backscattering effects in the inter-ONU transmission, the same experimental conditions as described in [9], are used. The optical spectrum at the ONU receiver is shown in the inset of Fig.…”

“…To this end, concurrent inter-ONU communication based on the hybrid OFDM DFMA PON is proposed and experimentally verified with offline signal processing in [9] by making simple alterations to the remote node (RN). This is performed by placing an optical circulator between one downstream output port and one upstream port of the RN coupler to redistribute and redirect the optical signal to each of the ONUs.…”

“…This paper presents a real time experimental validation of the aforementioned technique with FPGA-based real-time signal processing. Apart from the advantages described in [9], the demonstrated PON system offers the advantage of dynamic reconfigurability. This feature allows dynamic DSP-enabled RF spectral allocation of different channels to optimize performance.…”

Simultaneous Upstream and Inter Optical Network Unit Communication for Next Generation PON

“…IOC has also become important because of services such as peer to peer file sharing, interactive gaming, and cloud computing among users in the same PON. If the PON is used for mobile fronthaul then the propagation delay can be up to 200 micro seconds while the allowed delay for 5G is 250 micro seconds [6], so to reduce latency IOC can be used for mobile fronthaul. The same latency issues exist when PON is used for 5G mobile backhaul, which can be resolved if inter base station communication is implemented using IOC [7].…”