In this paper, a power sparse code division non-orthogonal multiple access (PSCD-NOMA) scheme is proposed for next-generation flexible optical access, which is based on the multi-stack network. All ...the optical network units (ONUs) are allocated with different power levels according to path loss to achieve power multiplexing. Compared with sparse code multiple access (SCMA), the proposed sparse code considers users' information as a whole, and a larger number of users can be implemented with relatively low complexity and similar or better performance. It can achieve 150% overload by sparse code. Moreover, an irregular-shaped 8 quadrature amplitude modulation (IS-8QAM) constellation diagram is devised that is more suitable for PSCD-NOMA. Orthogonal chirp division multiplexing (OCDM) is employed for its advantages of the stronger anti-dispersion ability. A 10.23 Gb/s PSCD-NOMA transmission over 25 km standard single-mode fiber is experimentally demonstrated. The results show that IS-8QAM can get at least 0.6 dB gain than the conventional 8QAM scheme. The difference in sensitivity between ONUs of different power levels is 2.8 dB, which corresponds to the loss between different paths. The sensitivity difference between different users at the same power level is only 0.3 dB, which indicates the proposed PSCD-NOMA has good fairness. PSCD-NOMA is a potential method for future optical access systems due to its great performance.
This paper reviews the key factors in the discussion and selection process before the launch of the higher speed passive optical network (PON) standards project in the Full Service Access Network and ...ITU-T SG15/Q2. It reviews the requirements for such a system and the progress of the related ITU-T standards documents. The key technologies necessary for the physical and protocol layers of the 50G-PON are also discussed.
In PON-based mobile fronthauls, direct inter-ONU communications without passing end-user traffic to the OLT offer a promising solution for fulfilling the stringent latency and bandwidth requirements ...of 5G and beyond networks. In this paper, with slight modifications to 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 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 digital filters 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.
In this article, we conduct an extensive investigation on our recently proposed greedy orthogonal frequency division multiplexing non-orthogonal multiple access (OFDM-NOMA) bit and power allocation ...(GONBP) algorithm, and further propose a novel margin-based OFDM-NOMA bit and power allocation (MONBP) algorithm for multi-user direct-detection (DD) OFDM-NOMA passive optical network (PON). Both algorithms allocate bits and power at both the user level and the subcarrier level by considering the frequency-selective fading effect of all users, the interaction/interference between users, and the constraint of total allocated bits for each user. 43-76 Gbit/s PON experiments where two optical network units have different transmission distances of 10-20 km and/or different received optical powers are performed. The results show that the proposed GONBP and MONBP outperform conventional OFDM-NOMA, discrete-Fourier-transform spread OFDM-NOMA, conventional greedy algorithm, and Chow's algorithm. Compared to GONBP, the proposed MONBP greatly reduces the complexity and achieves better performance especially when the signal-to-noise ratio profiles of ONUs are different, thus providing a promising solution for multi-user OFDM-NOMA PON.
Possible configurations of tunable components for the next-generation passive optical network stage 2 (NG-PON2) are reviewed on the basis of system requirements. Expected network functions in NG-PON2 ...systems along with the concept of in-service tuning in colorless ONUs are also reviewed.
In order to meet the ever-increasing traffic demands, the combination of fiber and Millimeter Wave (mmWave) is expected to play a key role for 5G Centralized-Radio Access Networks (C-RANs). Due to ...the inefficiency of the Common Public Radio Interface for the Baseband Unit (BBU)-Remote Radio Head (RRH) communication, analog-Radio-over-Fiber (a-RoF) technology is considered a promising solution, mainly due to the RRH simplification and lower fronthaul requirements it imposes. In such mmWave a-RoF C-RANs, efficient Medium Transparent-Medium Access Control (MT-MAC) protocols are needed able to meet the challenging 5G requirements. To this end, in this paper, we propose a gated service MT-MAC protocol which authorizes each user to transmit the amount of data it requested. A detailed delay model is proposed, which is validated through simulations for different fiber lengths, network load conditions and number of available optical wavelengths. Moreover, the proposed protocol is compared with the state-of-the-art (SoA) and is shown to achieve up to 20 times higher throughput, 2 times lower delay with 100% lower blocking probability and 5 times higher data wavelength utilization, while being able to adapt to varying network traffic conditions. Our proposal also attains sub-ms latency in most cases, constituting it a promising candidate for 5G mmWave a-RoF C-RANs.
We present a technique for remote monitoring of time-division multiplexed passive optical networks (TDM-PONs) based on fiber Bragg grating (FBG) encoders interrogated by a broadband incoherent ...optical frequency-domain reflectometer (I-OFDR). Compared with previous approaches, the proposed system features inherent high robustness against temperature-induced wavelength shifts in the FBG-encoders. The I-OFDR-based monitoring unit enables measurements with high resolutions and sensitivities without the need for high peak-power monitoring signals, which minimizes its footprint on the data links. We carry out a comprehensive description of the system and we evaluate its capacity in terms of signal-to-interference ratio (SIR). We show that, through suitable windowing, a SIR <inline-formula><tex-math notation="LaTeX">\geq</tex-math></inline-formula> 20 dB can be achieved in highly-dense TDM-PONs having more than 128 customers through the use of moderate measurement bandwidths of 300 MHz. We experimentally demonstrate the proposal in a TDM-PON carrying a 10 Gbps downstream data signals, obtaining a negligible impact in the downlink performance, such as the bit error rate remains below <inline-formula><tex-math notation="LaTeX">10^{-6}</tex-math></inline-formula>.
The power budget and costs are the two primary concerns for access networks. A major challenge is to minimize upstream power combining loss to increase the power budget. Spatial modes multiplexing ...offers the possibility to minimize upstream combining loss without significant added costs. We demonstrate the first integrated six-mode passive optical network, utilizing spatial modes to eliminate upstream combining loss. A record 4-dB net gain in power budget was achieved by fusion splicing a photonic lantern with a FMF, in contrast to the traditional power combining scheme with a single-mode power combiner/splitter. BERs <;10 -9 were obtained for all the six modes enabling Ethernet transmission using commercial GPON equipment. The packet loss of all six modal channels was tested for 12 h. Finally, we discuss some special issues of few-mode PON regarding its practical application.
In light of the 5G deployments, edge computing, and future high bandwidth services, the industry is rethinking the optical access network architecture design. Passive optical network (PON) with its ...efficient fiber infrastructure plays an essential role in this design transformation. This article reviews the driving forces shaping the new generations of PON systems in the coming years; and discusses the course of action in the FSAN Group, ITU-T, and IEEE standards bodies to address the impending requirements.
Fiber has been envisioned for delivering broadband services to the residential customer for over 30 years, yet it has only recently entered the mainstream. Currently, fiber-to-the-home (FTTH) is ...being installed in many countries at remarkable rates (even though it still constitutes only a fraction of all broadband lines in most countries). Other lightwave transmission technologies have progressed far faster. What has held FTTH up for so long? What improvements along the way have occurred? What recent changes have made it successful? This article follows the progress in moving fiber toward the home and major architectural changes that have reduced costs while increasing capabilities to meet today's needs.
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