Evolution from TDM-PON to WDM-overlaid PON employing a wavelength-conversion node

Grant management procedure for energy saving TDM-PONs

Time Division Multiplexing Passive Optical Networks (TDM-PONs) serve as a key enabler for the evolution of broadband access network infrastructure. As TDM-PONs adapt to support 6G networks, reducing energy consumption becomes increasingly critical. Sleep modes have been widely adopted as an effective energy-saving solution. However, their use can introduce delays that compromise performance. This issue becomes especially problematic in 6G PONs, where ultra-low latency and stringent service requirements leave minimal tolerance for delay-related inefficiencies. In this paper, we propose a novel sleep synchronization mechanism for both single and multiple TDM-PONs, allowing Optical Network Units (ONUs) to join one or more sleep/wake-up groups based on the service type and delay tolerance. Our practical design framework incorporates delay-based grouping and existing sleep modes to address the operational complexities of multi-PON systems while remaining fully compatible with current PON standards. The simulation results show that our approach satisfies the requirements of delay-sensitive traffic and achieves up to 37% energy savings. Compared to baseline methods such as adaptive scheduling and fixed-interval cyclic sleep, it offers a 15–20% improvement in the energy–delay trade-off. These results demonstrate the potential for near-term deployment of 6G PONs and lay the foundation for more advanced, delay-aware energy management strategies in next-generation optical access networks.

Simultaneous upstream and inter optical network unit communication for long reach PON using single transmitter and self-phase modulation

A deep learning based dynamic bandwidth allocation method for XG-PON based mobile fronthaul for CRAN

We propose a new technique for multiple-wavelength upstream transmission in time division multiplexed-passive optical networks using Fabry-Perot laser diodes (FP-LD) at optical network units (ONU). The FP-LD transmits at one of strategically separated seeding wavelengths from the optical line terminal enabling the ONUs to join one of few TDM upstream channels. The scheme increases upstream capacity without the use of costly, higher speed burst mode transceivers. We present experimental results showing that up to 9 upstream channels at 2.5 Gb/s data rate can be achieved with this scheme. The paper presents locking characteristics of the FP-LD relevant for this application such as suppression of other seeding wavelengths, minimum wavelength separation and burst mode operation.

For many emerging mobile broadband services and applications, the source and destination are located in the same local region. Consequently, it is very important to design access networks to facilitate efficient local data exchange. In the past few years, most existing studies focus on either the wired or wireless domains. In this paper, we aim to exploit both the wired and wireless domains. Specifically, we consider a fiber-wireless access network in which a passive optical network (PON), consisting of one optical line terminal and multiple optical network units (ONUs), connects densely deployed base stations. In such a scenario, we propose two novel access schemes to utilize both network coding and device association in the following two cases: each device can be associated with one ONU for uploading and downloading its data packets; and each device can be associated with two different ONUs for uploading and downloading its data packets, which are referred to as, the network coding design and symmetric device association (NCsDA) problem and the network coding design and asymmetric device association (NCaDA) problem, respectively. To understand the potentials of NCsDA, we first formulate a mixed integer nonlinear programming to minimize the weighted number of packet transmissions (WNT), which is related to both the energy consumption and system capacity. We then theoretically analyze the tight upper bounds of the minimal WNT in the PON, which helps us to approximate the NCsDA problem by mixed integer linear programming . We also give theoretical analysis on the NCaDA problem and formulate it as a mixed integer linear programming. Next, we develop efficient algorithms based on linear programming relaxation and give network coding designs to solve the NCsDA problem and the NCaDA problem. To validate our design, we conduct extensive simulations, which demonstrate the impact of important network parameters and the promising potentials of the proposed NCsDA and NCaDA schemes.

One of the major challenges in long reach passive optical network (LR-PON) is the longer end-to-end traffic delay between the central office (CO) and the end user. This longer delay significantly hampers the quality of services (QoSs) of the optical access networks. The QoSs of the LR-PON are easily affected by delaying or dropping packets as a consequence of parameters such as latency, jitter, bandwidth utilization and packet loss. Most of the studies have only focused on capacity allocation amongst the multiple optical network units (ONUs) of the network by the optical line terminal. Some research also proposed to schedule the packets in multiple threads based on the priority. However, due to the lacking of intra thread scheduling scheme the high priority (HP) data packet still suffering from more delay. In this paper, we propose a decentralized intrathread scheduling scheme that provides lower queuing delay as well as end-to-end packet delay of the HP traffic. The performance measurements involve several scenarios which combine different traffic types, intra ONU scheduling and queuing policies. The goal of this research is to identify the most suitable scenario to provide qualitative services and efficient resource utilization among different traffic types. The performances of the proposed scheme have been analyzed and compared with the existing scheme by numerical simulations. The numerical results proves the advantages of the proposed scheme over the existing one in terms of lower average packet delay of high priority data packets and higher network throughput under varying offered loads.

OTACT: ONU Turning with Adaptive Cycle Times in Long-Reach PONs

In 5th generation mobile communications systems (5G), the number of small cells with centralized-radio access network (C-RAN) architecture is expected to increase greatly. Time division multiplexing-passive optical networks (TDM-PON) are promising transmission systems for networks between a baseband unit (BBU) and a remote radio head (RRH). However, there is a challenge as regards the ultra-low latency requirements of 5G including less than 1 ms for end-to-end communication, because a TDM-PON generally transmits using time division multiple access (TDMA) as a basis. In this paper, we derive the achievable latency and the number of RRHs accommodable by TDM-PON, and analyze the applicable range of a TDM-PON for mobile use. Our analysis shows that it is possible to design a PON application in accordance with the latency requirements of mobile systems.

Passive optical networks (PONs) have recently emerged to be a promising approach to enhance the penetration of fiber towards the subscriber side, thus further enables delivery of higher data-rate services to the subscribers. They feature easy network maintenance as there is no active component at the remote node (RN). However, in conventional PONs, both upstream and downstream bandwidths have to be time-shared among all optical network units (ONUs). By applying WDM technique to PONs, the total system capacity can be further enhanced. Each ONU enjoys a dedicated bandwidth and resolves the ranging problem as in PONs. In both conventional PON and WDM-PON, little work has been done to offer protection capability though fiber fault detection methods have been extensively studied. We propose a novel network architecture for WDM-PON which offers 1:1 protection capability. In case of any fiber cut between remote node and ONUs, the affected ONU can re-route the wavelength channels via the adjacent ONU and can still maintain normal bidirectional traffic.

An ILP-based CapEx and OpEx efficient multi-stage TDM/TWDM PON design methodology

A survey of dynamic bandwidth allocation algorithms for Ethernet Passive Optical Networks

This paper introduces an in-service transmission surveillance and protection-based approach for fiber failures/faults over fiber-to-the-home passive optical network (FTTH-PON) with an excellent combination of Access Control System (ACS) and Smart Access Network Testing, Analyzing and Database (SANTAD). Our hardware design works on a standard local area network (LAN) using a specially designed hardware interfaced with a microcontroller integrated Ethernet to monitor the status of optical signals flow and provide the restoration against fiber failures/faults in FTTH-PON. We also introduce the centralized management and access control program by means of SANTAD. ACS is used to control the troubleshooting mechanism carried out by SANTAD. This design will be implemented at central office (CO) for distant monitoring and remote controlling each optical fiber line’s status as well as for detecting any failures/faults that occurs in the network system downwardly from CO towards multiple optical network units (ONUs). The scope of this discussion only highlighted on the monitoring and controlling instead of the restoration scheme.

Many diverse high bandwidth consumers of different quality of service (QoS) requirements can currently be well supported by the last mile candidate—gigabit Ethernet passive optical network (GE-PON) system. Through modeling the performance of TCP over GE-PON in terms of fairness among multiple optical network units (ONUs) and multiple transmission protocols, the results indicate that TCP flows will suffer from restraining windows when competing with other TCP or other protocol flows, such as UDP protocol flows. Therefore, this paper proposes an adaptable approach to promote the throughput of restraining TCP flows to achieve TCP fairness. This paper focuses on the potential benefits of such a recovery modification process for TCP flows. TCP flows are always considered as the low -priority services and suffer from best-effort delivery. The comparison in both experiments and simulations shows that restraining window elastic recovery (RWER) can improve inter-protocol fairness and achieve the TCP throughput enhancement.

A novel broadcast/multicast-capable carrier-reuse WDM-PON architecture is proposed. Utilizing the splitting capability of a power splitter and the cyclic property of an arrayed waveguide grating (AWG) at the remote node, the broadcast channel and a dedicated downlink unicast channel can be overlaid and subsequently transmitted to each optical network unit (ONU) simultaneously. Since each ONU can receive a common broadcast channel with electronically coded information, the multicast function can be implemented in a higher layer, similar to the current multicast-capable E-PON or G-PON using IP multicast addresses through a single wavelength channel. Thus, there is no need for reconfiguration of physical connections for multicast services. The proposed approach is different from the approach of overlaying DPSK multicast data onto NRZ unicast data using the same wavelength. As such, this approach does not require an expensive DPSK receiver at each ONU, and high receiver sensitivity can be achieved since there is no need to restrict the extinction ratio (ER) of the NRZ unicast data to a small value. Simulation studies show that this WDM-PON provides acceptable performance with one 10 Gb/s broadcast channel and thirty-two 10 Gb/s downlink unicast channels, and thirty-two 2.5 Gb/s uplink unicast channels. Another advantage of this WDM-PON is that the broadcast channel only causes a small interference with the downlink/uplink unicast channels, and it is shared by all the ONUs. The effect of the optical carrier to subcarrier ratio on the bit error rate performance can be mitigated by increasing the extinction ratio of the delay interferometer used at the remote node.