Passive Optical Network Research Articles

A novel DWDM-based comb source for future optical network

In recent times, there has been enormous growth in internet-based applications such as online entertainment platforms, video conferencing and voice over internet protocol (VoIP) applications which might be the trend in future. In order to support such bandwidth-hungry applications, the speed of the network should be enhanced. Increasing the infrastructure of the network requires heavy investment. Another alternative to increase the capacity of the network is to use dense wavelength division multiplexing (DWDM) which also results in increased costs as the lasers and other equipment needed for generation of wavelengths are required. In this work, an alternative cost effective technique is used to create a DWDM scenario using optical flat comb source (OFCS) by combining amplitude modulator (AM) and single drive mach zehnder modulator (SD-MZM). The spectral lines generated using this procedure can be used in Passive Optical Network (PON) as input sources. In this paper, 51 flat spectral lines are generated and transported over a distance of 100 km which are also capable of supporting a data rate of greater than 10 Gbps in a single spectral line.

Capacity Improvement of 3D-OCDMA-PON Hybrid System Next Generation Using Weight Zero Cross Correlation Code

This paper proposes a novel code for optical code division multiple access (OCDMA) systems, called the three-dimensional (3D) spectral/temporal/spatial single weight zero cross-correlation (3D-SWZCC) code. The proposed code could potentially be used in the next generation of passive optical networks (NG-PONs) to provide a 3D-SWZCC-OCDMA-NG-PON system. The developed code has a high capacity and a zero cross-correlation property that completely suppresses the multiple access interference (MAI) effects that are a main drawback for OCDMA systems. Previously, a two-dimensional (2D) SWZCC code was proposed for two-dimensional OCDMA (2D-OCDMA) systems. It works by devoting the first and second components to spectral and spatial encodings, respectively. However, the proposed code aims to carry out encoding domains in spectral, time, and spatial aspects for the first, second, and third components, respectively. One-dimensional, 2D, and 3D systems can support up to 68, 157, and 454 active users with total code lengths equal to 68, 171, and 273, respectively. Numerical results reveal that the 3D-SWZCC code outperforms codes from previous studies, including 3D codes such as perfect difference (PD), PD/multi-diagonal (PD/MD), dynamic cyclic shift/MD (DCS/MD), and Pascal’s triangle zero cross-correlation (PTZCC), according to various metrics. The system function is provided by exhibiting the architecture of the transmitter and receiver in the PON context, where the proposed code demonstrates its effectiveness in meeting optical communication requirements based on 3D-OCDMA-PON by producing a high quality factor (Q) of 18.8 and low bit error rate (BER) of 3.48 × 10−29 over a long distance that can reach 30 Km for a data rate of 0.622 Gbps.

Time-aware deterministic bandwidth allocation scheme in TDM-PON for time-sensitive industrial flows

A programmable logic controller deployed in the cloud or edge cloud (cloud PLC) contributes to flexible and scalable industrial manufacturing processes. For the industrial Internet, a time-division multiplexing passive optical network is a promising access technology for connecting cloud PLC and industrial devices. Time-sensitive (TS) industrial applications such as motion control and mobile robotics impose strict delay and jitter requirements, pursuing deterministic transmission capability, that is, guaranteeing that the upper bounds on delay and jitter of the TS industrial flow meet its requirements. However, traditional bandwidth allocation schemes aim to leverage statistical multiplexing to improve bandwidth resource utilization efficiency, so it guarantees only the “average delay/jitter” of the service and cannot meet the deterministic requirements of the TS industrial flow. This paper presents a time-aware deterministic bandwidth allocation (TA-DetBA) scheme to satisfy the deterministic transmission of TS industrial flows. To this purpose, first, we constrain the position of the transmission window (i.e., bandwidth) allocated by optical line termination to the optical network unit according to the arrival characteristics (i.e., flow arrival time and flow cycle) and requirements (i.e., delay and jitter) of the flow. Subsequently, we propose an integer linear programming scheduling model and a greedy-based time slot equalization heuristic scheduling algorithm to improve schedulability and reduce the average delay of best-effort flows. Simulation results show that our proposed TA-DetBA scheme guarantees the deterministic delay and jitter of TS industrial flow. Compared with the fixed bandwidth allocation (FBA) scheme, the average resource utilization efficiency of the TA-DetBA scheme is improved by up to 20.6% higher than FBA.

DRL-assisted joint allocation of antenna, radio, and front-haul resources in TWDM-PON-based NG-RANs with mMIMO-enabled beamforming

The high spectrum efficiency of massive multiple input multiple output (mMIMO)-enabled beamforming is attractive for solving the massive number of connections in next-generation radio access networks (NG-RANs). However, the beamforming based on multiple antenna sub-arrays to support multi-connections would introduce extra 2D antenna sub-array selection and radio resource block (RB) allocation; meanwhile, considering the front-haul bandwidth consumption would reduce as much as possible the redundant data transmitting over front-haul in the NG-RANs. Therefore, a key issue is how to coordinate 2D antenna sub-array selection and radio RB allocation to minimize the front-haul bandwidth and maximize the radio RB utilization when accommodating a set of beam antenna array (BAA) requests. In this paper, we first establish a 3D BAA mapping model to jointly optimize 2D antenna sub-array selection and radio RB allocation, which would in turn affect the allocation of the front-haul wavelength bandwidth in a time and wavelength division multiplexed passive optical network (TWDM-PON)-based front-haul with the mMIMO antenna system. An integer linear programming mathematical model is formulated, and a novel deep reinforcement learning (DRL)-based algorithm is proposed to optimize the front-haul bandwidth and radio RB utilization. Besides, two heuristic algorithms are developed with different antenna sub-array selection policies as the benchmarks. The extensive simulation results show that our proposed DRL-based algorithm can attain the lowest average cost (AC) for different numbers of BAA requests considered by seeking the optimal trade-off between the front-haul bandwidth consumption and the number of the used antennas. Compared with the inter-sub-array benchmark, the DRL-based algorithm can achieve up to 7.5% AC reduction, which is mainly attributed to the 21.2% reduction of the front-haul bandwidth without increasing the number of used antennas.

400-Gbps/80-km Rate-Flexible PCS-64-QAM WDM-CPON With Pseudo-m-QAM Chaotic Physical Layer Encryption

For next-generation high-capacity, rate-flexible, and secure 400-G passive optical network (PON), a scheme joint wavelength division-multiplexed (WDM), entropy-regulated probabilistic constellation shaping-64-quadrature amplitude modulation (PCS-64-QAM) and chaotic encryption mapping, is proposed and demonstrated. For the first time, chaotic encryption is realized over the PCS-based PON with the architecture from one optical line terminal (OLT) to multiple optical network units (ONUs). Chaotic encryption with an initial-value-sensitive feature can generate a large amount of parallel encrypted sequences which provide a key pair corresponding with every possible entropy/rate. A novel mapping from PCS-64-QAM with various entropies to pseudo- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> -QAM is designed, which erases the entropy information of the link and encrypted the original information of the sequence. The encryption transmission is demonstrated over a real-time dual-polarized coherent optical platform with an 80-km link and typically one-to-many PON configuration, and a net 211.80∼348.12-Gb/s rate result within the hard-decision forward error correction (FEC) threshold is achieved for 6λ × 2 ONUs group. The rate of each polarization state can be tuned in a minimum 3.408-Gbps step in the demonstration. Expanding from the basis of the original WDM-CPON, this work prepares an adapted chaotic encryption scheme for large-scale access. Overall, our proposed scheme can provide an abundant system loss budget, a large rate tunable range, and basic physical layer security for next-generation rate-flexible coherent PON (FLCS-CPON).

Laser Sharing Uplink Polarization Division Multiplexing FBMC Passive Optical Network

In this paper, we proposed and experimentally demonstrated a laser sharing filter bank multicarrier passive optical network (FBMC-PON) uplink architecture, to provide high spectrum efficiency frequency division multiple access (FDMA) to the optical network terminals (ONTs) with aggregated uplink data rate of up to 100 Gb/s/λ for each optical network unit (ONU), in a fiber to the frontage (FTTF) scenario utilizing existing copper infrastructure. Intensity modulation (IM) and heterodyne detection are implemented, combined with polarization division multiplexing (PDM) to double the system capacity. The uplink performance of FBMC-PON is emulated with two asynchronous ONT bands in transmission over 20 km single mode fiber (SMF). FBMC with prototype filters (PFs) PHYDYAS, extended Gaussian filter (EGF) and isotropic orthogonal transform algorithm (IOTA) is discussed in comparison with orthogonal frequency division multiplexing (OFDM) in terms of frequency guard band and multiple access interference (MAI). The laser from an external cavity laser (ECL) is split and shared among ONTs. The experimental results show that FBMC can achieve significant improved receiver sensitivity compared to OFDM in the asynchronous uplink. FBMC with PHYDYAS can avoid MAI with frequency guard interval of one time the subcarrier spacing. With optical receiving power (ROP) of −23 dBm, to support 2, 4 and 8 ONTs, the required optical power of the narrow linewidth laser is respectively 10, 16 and 22 dBm with bit error rate (BER) at the hard decision forward error correction (HD-FEC) threshold.

Efecto de la técnica de modulación M-QAM para una infraestructura de red convergente Radio sobre Fibra (RoF)

The objective of the research is to analyze, at the simulation level, the effect of the M-Quadrature Amplitude Modulation (M-QAM) technique, in the downlink, for a converged Radio over Fiber (RoF) network infrastructure, implementing the Ortho-gonal Frequency Division Multiplexing (OFDM) technique and the Passive Optical Network architecture, with 10 Gbps capa-city (XG-PON). The evaluation of the effect of the M-QAM modulation technique was done through a pre-established simulation methodology and using the optsim sof-tware for the network model and tests. In the results of the research, the increase of the order of M-QAM modulation for a con-verged OFDM-RoF network infrastructure allows to represent more bits per symbol, however, it requires a higher transmission power. The conclusion derives in the pos-sibility of developing a robust converged OFDM-RoF network infrastructure of XG-PON type, implementing the M-QAM tech-nique, since it efficiently uses the available bandwidth.

Passive IoT Optical Fiber Sensor Network for Water Level Monitoring with Signal Processing of Feature Extraction

This paper presents a real-time remote water level monitoring system based on dense wavelength division multiplexing (DWDM)-passive optical fiber sensor (OFS) network for the application of the Internet of Things (IoT). This network employs a broadband light source based on amplified spontaneous emission (ASE) as a seed light. This ASE light is spectrum-sliced by an athermal type arrayed waveguide grating (200 GHz × 16 channel), then distributed towards multiple sensing units (SU). Here, 16 SUs are installed vertically at the specified height in the water pool according to the design specification (i.e., spatial resolution). Then, each SU reflects an optical spectrum having a different reflection coefficient depending on the surrounding medium (e.g., air or water). By measuring these reflected optical spectra with an optical spectrum analyzer, the water level can be easily recognized in real time. However, as the sensing distance increases, system performance is severely degraded due to the Rayleigh Back-Scattering of the ASE light. As a result, the remote sensing capability is limited at a short distance (i.e., &lt;10 km). To overcome this limitation, we propose a simple signal processing technique based on feature extraction of received optical spectra, which includes embedding a peak detection algorithm with a signal validation check. For the specific, the proposed signal processing performs the peak power detection, signal quality monitoring, and determination/display of the actual water level through three function modules, i.e., data save/load module, signal processing module, and Human–Machine Interface display module. In particular, the signal quality of the remote sensing network can be easily monitored through several factors, such as the number of spectral peaks, the wavelength spacing between neighboring peaks and the pattern of detected peak power. Moreover, by using this validation check algorithm, it is also possible to diagnose various error types (such as peak detection error, loss of data and so on) according to the pattern of measured optical spectra. As a result, the IoT sensor network can recognize 17 different level statuses for the water level measurement from a distance of about 25 km away without active devices such as optical amplifiers (i.e., passive remote sensing).

Efficiency enhancement of long-reach passive optical network using the polarization coding

Abstract This paper, propose a new passive optical network (PON) system structure based on the two orthogonal polarization states of the same wavelength. This method is usually applied to increase the number of simultaneous users in the network, it can double the number of potential users. The proposed technique utilized to increase split ratio and consequently increase the reach and the split ratio. This can be achieved by implementing technologies such as power splitter. In terms of bit rate, the proposed PON offers a bit rate of 10 Gbps for downstream transmissions. The results obtained in this work are shown that the proposed system can accommodate more users simultaneously for the typical Q factor is greater than 6.

Series Editorial: Optical Communications and Networks

In the first issue of the Optical Communications and Networks Series in 2023, we have selected six fascinating articles reporting on recent advances in optical communications and networking. They address free-space optical (FSO) communications including visible light communication (VLC), intelligent fiber-optic communications leveraging machine learning (ML), passive optical network (PON) technology for industrial networks, and dynamic optical path provisioning for alien access links.

Enabling Next-Generation Industrial Networks with Industrial PON

Traditional industrial networks primarily focus on onsite device operation and worker safety. They do not engage in the ongoing digital transformation with remote control machinery and big data processing. The next-generation of industrial networks is expected to offer high-speed connectivity, intelligent management, and flexible architecture to adapt to technology advances and business competitions. Data from the environment, machinery, and offices should be collected and analyzed to support automated procedures related to an industry. In this article, a network architecture based on the passive optical network (PON) technology, the so-called industrial PON, is proposed to enable the next-generation industrial networks. It manages the network resource via a three-layer structure. Recent industrial PON implementations deployed by a Tier 1 operator are investigated in detail to evaluate the solution feasibility and network performance. Results demonstrate that the industrial PON can connect various business assets, provide data exchange to automate industrial processes, and manage the business to improve production efficiency.

Multi-OLT PON-based open access network for multi-service performance tuning via the Event-Horizon algorithm

A multi-optical line terminal (multi-OLT) passive optical network (PON) is gaining attention for its multi-access, wide coverage, and integration capabilities. It outperforms conventional single OLT PON, reducing operational complexities, packet delay, and loss. A novel multi-OLT PON-based open-access network (OAN) architecture is proposed that integrates various service providers (SPs) as well as different access networks. Optical network unit structure is also designed to support differential access. The challenging issue here is to incorporate heterogeneous SPs and provoke downstream service with their application diversity. This paper presents what we believe is a novel algorithm named Event-Horizon (EH) to afford heterogeneous downstream services from different SPs for IEEE PONs [Ethernet PON (EPON) and 10 gigabit EPON (10G EPON)]. It incites SP competitiveness and ensures a user experience of seamless migration from service to service. Downstream resource allocation is an atypical issue in the PON area. There are reported numerous online schemes with prediction for the upstream side. Since network data is highly bursty and unpredictable, the EH algorithm uses the machine-learning-based bootstrapping method as its prediction tool. The algorithm improves downstream performance by four distinctive features. First, bandwidth is guaranteed among shared SPs according to service level agreements. Second, bandwidth is allocated for reported data; then excess bandwidth is reallocated as predicted (by bootstrapping) differed data. Third, a donor SP preserves margin before excess bandwidth release, which is a nonlinear process featuring network dynamics. Fourth, the margin satisfaction factor is formulated for tuning multi-service user satisfaction according to quality of service. The simulation is performed by a model OAN showing an emergency medical wireless sensor network (WSN) as the master shareholder OLT and a fiber to the home (FTTH) as a subsidiary one. Performance tuning on the margin reservation of 1% for the WSN case study shows 99.4% network efficiency with maximum jitter of 50 µs up to the full load owing 97.26% throughput. Network delay justifies CISCO and ITU-T requirements for real-time IP traffic. FTTH experiences the packet loss of 0.68% using the EH algorithm at the full load, maintaining WSN emergency service packet loss&lt;0.003%.

Merging engine implementation for intra-frame sharing in multi-tenant virtual passive optical networks

High up-front capital expenditures impede the widespread deployment of passive optical networks (PONs). A multi-tenant solution, in which multiple network operators virtually share PON infrastructure and bandwidth resources, can result in significant cost savings. First, we investigate the viability of virtual PONs, in which virtual network operators share a portion of the upstream bandwidth in a frame. Each PON schedules its frame-level capacity using a dedicated dynamic bandwidth assignment algorithm, resulting in the generation of an independent bandwidth map (BMap). Second, we implement at the optical line terminal a merging engine that combines individual virtual BMaps into a single physical BMap, which is then transmitted to all optical network units. Our novel traffic merging algorithm is capable of consolidating traffic across all transmission containers. We apply this merging engine on top of the 10-Gbit-capable PON module and validate our approach using network simulator 3. The results show that our proposed intra-frame sharing technique, when integrated with our traffic merging algorithm, significantly outperforms the standard inter-frame sharing approach in terms of both latency and packet loss. Furthermore, we observed that best-effort traffic is affected most for all resource constraint scenarios of intra-frame sharing.

Simulative study of high speed light modulated measured sources for high optical network transmission efficiency

Abstract This study reported the performance evaluation and simulation of passive optical networks for high transmission rates up to 10 Gb/s for possible distance up to 50 km. Laser rate equations, directly modulated laser measured and vertical cavity surface emitting laser (VCSEL) are employed for the measurement of the network performance. Different bit sequences are suggested to show the network performance parameters with various proposed optical sources. Optical and electrical powers are measured for 50 km network reach. In addition to max. Q factor is also measured for various optical sources and bits sequence variations. Laser rate equations are employed in this network to upgrade the Q factor criteria for maximum network reach of 100 km in the downstream direction.

50G-next generation passive optical networks stage 2 using millimeter wave over fiber technique under the ITU-T G.9804 standardization

50G-next generation passive optical networks stage 2 using millimeter wave over fiber technique under the ITU-T G.9804 standardization

Faulty branch identification in passive optical networks using machine learning

Passive optical networks (PONs) have become a promising broadband access network solution thanks to their wide bandwidth, low-cost deployment and maintenance, and scalability. To ensure a reliable transmission, and to meet service level agreements, PON systems have to be monitored constantly in order to quickly identify and localize network faults and thus reduce maintenance costs, minimize downtime, and enhance quality of service. Typically, a service disruption in a PON system is mainly due to fiber cuts and optical network unit (ONU) transmitter/receiver failures. When the ONUs are located at different distances from the optical line terminal, the faulty ONU or branch can be identified by analyzing the recorded optical time domain reflectometry (OTDR) traces. OTDR is a technique commonly used for monitoring of fiber optic links. However, faulty branch isolation becomes very challenging when the reflections originate from two or more branches with similar length overlap, which makes it very hard to discriminate the faulty branches given the global backscattered signal. Recently, machine learning (ML)-based approaches have shown great potential for managing optical faults in PON systems. Such techniques perform well when trained and tested with data derived from the same PON system. But their performance may severely degrade if the PON system (adopted for the generation of the training data) has changed, e.g., by adding more branches or varying the length difference between two neighboring branches, etc. A re-training of the ML models has to be conducted for each network change, which can be time consuming. In this paper, to overcome the aforementioned issues, we propose a generic ML approach trained independently of the network architecture for identifying the faulty branch in PON systems given OTDR signals for the cases of branches with close lengths. Such an approach can be applied to an arbitrary PON system without requiring to be re-trained for each change of the network. The proposed approach is validated using experimental data derived from the PON system.

Time-Series Representation Learning in Topology Prediction for Passive Optical Network of Telecom Operators

The passive optical network (PON) is widely used in optical fiber communication thanks to its low cost and low resource consumption. However, the passiveness brings about a critical problem that it requires manual work to identify the topology structure, which is costly and prone to bringing noise to the topology logs. In this paper, we provide a base solution firstly introducing neural networks for such problems, and based on that solution we propose a complete methodology (PT-Predictor) for predicting PON topology through representation learning on its optical power data. Specifically, we design useful model ensembles (GCE-Scorer) to extract the features of optical power with noise-tolerant training techniques integrated. We further implement a data-based aggregation algorithm (MaxMeanVoter) and a novel Transformer-based voter (TransVoter) to predict the topology. Compared with previous model-free methods, PT-Predictor is able to improve prediction accuracy by 23.1% in scenarios where data provided by telecom operators is sufficient, and by 14.8% in scenarios where data is temporarily insufficient. Besides, we identify a class of scenarios where PON topology does not follow a strict tree structure, and thus topology prediction cannot be effectively performed by relying on optical power data alone, which will be studied in our future work.

Predicting the performance of broadband passive optical networks using machine learning

Abstract Broadband passive optical networks is an established architecture for the high-speed data transfer. For effective fault diagnosis and self-configuration in these networks, analysis of network-generated data is essentially required. In this era, machine learning-based data analytics approaches could play a vital role in analyzing the performance of the networks. In this paper, a machine learning approach has been proposed for predicting the performance of broadband passive optical networks. For this task, a dataset consisting of fiber length, transmission power, number of power splitters, line width, and extinction ratio parameters has been generated to make an estimate of the Q factor for a given optical network. Out of these network parameters, fiber length, transmission power, and several power splitters are selected through the relief attribute evaluation technique. The selected parameters are fed into a regression-based model tree classification algorithm for estimating different levels of Q factor. This work also takes into account logistic regression, decision tree, decision table, PART, and random forest algorithms for the desired task. The analysis of simulation results proves that the regression-based model tree classification algorithm provides an effective estimate of Q factor in terms of accuracy of 93.23% and 95.74% for 7-class and 3-class problems. Thus, this algorithm appears to be a suitable choice to predict the performance of broadband passive optical networks accurately.

Wheel-Based MDM-PON System Incorporating OCDMA for Secure Network Resiliency

Wheel-based network resilience passive optical network (PON) based on mode division multiplexing (MDM) can be integrated with optical code division multiple access (OCDMA) schemes efficiently for the fixed and backhaul traffic under normal and break/failure fiber operating conditions. In this work, a bidirectional 10/2.5 Gbit/s hybrid MDM-OCDMA-PON system using multi-weight zero cross-correlation (MWZCC) code is proposed. Donut modes 0 and 1 are incorporated by the MDM technique in the proposed system. The benefit of this work is to offer an inexpensive, high-bandwidth and advanced long-haul network with satisfactory resource utilization ability for fiber links with protection against faults and to improve the reliability along with survivability of the network. The simulation results show the successful realization of the multimode fiber (MMF) link at 1.6 km in the uplink and 1.2 km in the downlink directions under an acceptable bit error rate (BER). The minimum accepted received power of −31 dBm in uplink and −27 dBm in downlink over 1 km link at 10/2.5 Gbit/s rate is obtained. Moreover, the minimum received power of −20 dBm in uplink and −30 dBm downlink is achieved by using MWZCC code compared to other codes handling 58 simultaneous end users. Further, the influence of fiber impairments and connected devices on the proposed approach is numerically evaluated. Moreover, it is shown that the wheel based proposed approach performs well than other topologies for the bidirectional network resilience transmission.

Suppression of Nonlinear Optical Effects in DWDM-PON by Frequency Modulation Non-Coherent Detection

We propose a simple and cost-effective method, using a direct frequency modulation (FM) and noncoherent detection (NCD) scheme, to suppress the nonlinear optical effects in dense wavelength division multiplexed (DWDM) optical communication. The FM transmitter comprises a directly modulated distributed feedback laser and a saturable semiconductor optical amplifier. In the NCD receiver, an optical slope filter as the FM to intensity modulation (IM) signal convertor is placed before a conventional photodetector. Because the FM signal has more evenly distributed optical power, bit-pattern-dependent nonlinear effects are consequently suppressed. After analyzing the nonlinear effects in the FM-NCD system and traditional IM direct detection (IM-DD) system, we found that the minimum achievable BER of the proposed FM-NCD scheme is 40 dB smaller. Moreover, a 2 Tbps (10 Gb/s × 200 channels) capacity was achieved by the FM-NCD system in 100 km DWDM passive optical networks (PONs), which is twice the capacity of the IM-DD system (10 Gb/s × 100 channels) under the same condition. These results indicate that WDM-PONs with the cost-effective FM-NCD scheme are strong candidates for future broad access networks and show great potential for the combination of optical access and metro networks for future generations of PONs.