Time-division Multiplexing Passive Optical Network Research Articles

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

In the context of 5G and beyond era, the use of Time Division Multiplexed Passive Optical Network (TDM-PON) for mobile fronthaul (MFH) in centralized/cloud radio access network (CRAN) has proven to be an optimal solution for addressing low-latency requirements. While existing literature has predominantly focused on optimizing mobile fronthaul latency rather than end-to-end latency, this paper introduces an end-to-end latency model for TDM-PON, specifically within a 10-gigabit Passive Optical Network (XG-PON) based MFH for CRAN. The paper then proposes an Intelligent Dynamic Bandwidth Allocation (DBA) scheme to minimize end-to-end latency of the network. The proposed scheme predicts the buffer occupancy reports using deep learning techniques at optical network units (ONUs). Thereafter, optical line terminal (OLT) schedules the available bandwidth using conventional DBA schemes (Group-GIANT i.e., Ggiant, Optimized Round Robin, Dynamic Service Interval). Primarily, the proposed DBA scheme transforms conventional DBA schemes (Ggiant, Optimized Round Robin, Dynamic Service Interval) into Intelligent versions (Intelligent Ggiant, Intelligent ORR, Intelligent DSI), showcasing a reduction of 28.63 %, 45.86 %, and 48.60 % in end-to-end latency in the XG-PON-based MFH for CRAN. Further, the analysis of obtained results has confirmed the supremacy of the Intelligent DSI DBA scheme over the Intelligent Ggiant and the Intelligent ORR DBA scheme.

Cyclic transmission window-based bandwidth allocation scheme for asynchronous time-sensitive industrial applications in TDM-PON

The industrial Internet has become an important application scenario for time-division multiplexing passive optical networks (TDM-PONs). Time-sensitive (TS) industrial applications, such as control-to-control communications, require a TDM-PON to have deterministic transmission capability. Traditional bandwidth allocation schemes are unable to fulfill this capability; thus we proposed a time-aware deterministic bandwidth allocation (TA-DetBA) scheme to guarantee deterministic delay and jitter in our previous work. TA-DetBA allocates appropriate transmission windows (TWs) to each TS industrial flow in a supercycle based on the flow’s arrival time, cycle, delay, and jitter requirements. However, “awaring” the arrival time of flow relies on precise time synchronization between the TDM-PON and industrial devices, which makes TA-DetBA unsuitable for those TS industrial applications that are asynchronous to the TDM-PON. In addition, the diversity of flow cycles may make the size of the supercycle and the number of allocated TWs large, thus increasing the complexity of the TW scheduling algorithm. To this end, we propose a cyclic TW-based deterministic bandwidth allocation (CTW-DetBA) scheme for asynchronous industrial applications. First, we design cyclic TWs with appropriate cycle and size for TS industrial flows, which not only improves the schedulability of TWs (i.e., the ratio of the number of successfully scheduled TWs to the total number of TWs) but also reduces the complexity of the algorithm. Then, we construct a TW scheduling model based on the satisfiability model theory to schedule the TWs in the PON upstream frame. Simulation results show that the CTW-DetBA guarantees the deterministic transmission of TS industrial flows that are asynchronous to the TDM-PON system. Compared with the fixed bandwidth allocation scheme, the average schedulability of the CTW-DetBA can be increased by up to 62.03%, and the average resource utilization efficiency can be increased by up to 20.4%.

Demonstration of 200 Gb/s/λ PON in O-Band With High-Bandwidth TFLN Modulator

As the broadband applications continue rising, the solutions of high-speed passive optical network (PON) with large power budget are highly desired. Direct detection scheme combined with digital signal procession (DSP) has been considered as a promising candidate due to its low cost, low power consumption and simple architecture. In this paper, we experimentally demonstrate 200 Gb/s/λ and 240 Gb/s/λ time division multiplexed passive optical network (TDM-PON) downstream transmissions based on four-level pulsed amplitude (PAM-4) modulation with direct detection in O-band. A high bandwidth thin film lithium niobate modulator is adopted to generate high Baudrate optical signal at the optical line terminal (OLT) side. A pre-amplified semiconductor optical amplifier SOA is employed at the optical network unit (ONU) side to improve the power budget. Several DSP algorithms are studied to compensate the linear and nonlinear distortions. We also propose a simplified Volterra nonlinear equalizer (S-VNLE) to reduce the computational complexity. Considering the soft-decision FEC (SD-FEC) threshold (1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> ), over 29 dB and 28 dB power budgets are achieved respectively for 200 Gb/s/λ and 240 Gb/s/λ PON system after 20 km standard single mode fiber (SSMF) based on our proposed S-VNLE.

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.

Local Oscillator Power Adjustment-Based Adaptive Amplification for Coherent TDM-PON With Wide Dynamic Range

Coherent technology is a promising solution for future 100-Gb/s and even 200-Gb/s single-wavelength time-division multiplexing passive optical network (TDM-PON) systems. One of the key issues for coherent TDM-PON is the upstream burst-mode amplification. The limited resolution of the analog-to-digital converter (ADC) makes it challenging to detect burst signals with widely varying power levels. Local oscillator (LO) power adjustment is a promising solution to this problem. In the present study, we verified the feasibility of LO power adjustment for adaptive amplification in a 200-G coherent TDM-PON system. We investigated the overall performance of the system under different implementation conditions, such as ADC sampling scales, TIA MGC mode control voltages, LO optical power levels, and the received optical power (ROP). Simulation and experimental results indicated that LO power adjustment can widen the dynamic range of the coherent PON system. As a proof of concept, we tested the system performance with continuous-mode signals and signals of isolated patterns with a burst-mode data frame. The dynamic range was extended to >30 dB via LO power adjustment, with 38- and 37-dB power budgets for 200-Gb/s/λ coherent TDM-PON continuous signals and signals of isolated patterns, respectively, after a 50-km standard single-mode fiber (SSMF).

Enhancing coordinated multi-point joint reception with dynamic bandwidth allocation

Coordinated Multipoint (CoMP) Joint Reception (JR) is a vital technology to mitigate uplink inter-cell interference (ICI) and can be facilitated by the centralized radio access network (C-RAN). In C-RAN architecture, base stations (BSs) are decoupled into the central unit (CU) and the distributed units (DUs). Meanwhile, a fronthaul (FH) is employed to connect CU and DUs. However, FH constructed by the time division multiplexing passive optical network (TDM-PON) significantly affects the performance of JR. The inherent polling mechanism of TDM-PON results in the asynchronous forwarding of JR data, which leads to high JR latency and a large amount of storage consumption. To alleviate the problem, we presented a novel dynamic bandwidth allocation (DBA) scheme, which classifies network data as JR and non-JR data and optimizes the data forwarding order of different types and DUs. A heuristic algorithm called Rearrange Sub-timeslot DBA (RS-DBA) was proposed to implement the DBA scheme. Simulation results indicate the proposed RS-DBA algorithm can reduce the average latency of JR data and storage resources consumption. In addition, the RS-DBA can make a better tradeoff between latency and efficiency.

TDM-PON and LTE-A Based Cost-Efficient FiWi Access Network Deployment

In recent times, usage of fixed wireless access (FWA) is gaining momentum even though fiber based existing services such as fiber-to-the-home (FTTH) are widely used for home Internet applications. We explore a time-division multiplexing passive optical network (TDM-PON) and long term evolution advanced (LTE-A) based cost-efficient access network planning strategy for combined usage of FWA and FTTH with the same network infrastructure. The proposed fiber-wireless (FiWi) access network satisfies all feasibility constraints and users’ quality of service (QoS) requirements. The proposed planning method judiciously identifies the network architecture and user service mode (FWA/FTTH).

A novel dynamic bandwidth allocation scheme towards improving the performance of XG-PON system

Time division multiplexed passive optical networks (TDM-PONs) such as EPON, XG-PON, XGS-PON, etc. have become widely accepted network architectures for meeting the bandwidth requirement of high-end consumer applications. The available bandwidth is still limited and needs to be utilized efficiently. There are scenarios when one ONU may completely dominate the network bandwidth leading to starvation of another ONUs. This may happen for an ONU in every allocation cycle. This enforces the OLT to provide such a fair allocation scheme that would provide a chance to different ONUs during polling and scheduling mechanism. This paper presents two novel DBA schemes namely the analytic hierarchy process proportional allocation scheme (AHP-PAS) and weighted sum model proportional allocation scheme (WSM-PAS) to determine the order of a transmission container (T-CONT) of an ONU for polling and scheduling. The proposed schemes are implemented in the network simulator (NS-3) and compared with the existing proportional allocation scheme (PAS) for inter-ONU and intra-ONU. The obtained results confirm that the proposed DBA schemes significantly improve the network performance in terms of delay fairness index, upstream mean delay, packet loss ratio, and packet jitter for T-CONT 2, 3, and 4.

Colorless Coherent TDM-PON Based on a Frequency-Comb Laser

Coherent reception becomes an interesting option when data rates in time-division-multiplexed (TDM) passive optical networks (PONs) grow beyond 50 Gbit/s. Controlling the wavelength, i.e., the optical frequency, and the phase of the laser acting as local oscillator (LO) is one of the main technical challenges in the design of coherent TDM PONs. In the optical network units (ONUs), low-cost lasers are required, which come at the expense of wavelength variations and drifts over multiple nanometers due to fabrication imperfections, and temperature variations. This contradicts the requirement of wavelength-stable LOs in coherent receivers. The use of a wavelength locker circuit and a temperature controller is considered as too complex for applications in access networks. In this work, we propose a novel colorless coherent architecture with high resilience to ONU laser wavelength drifts of up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 4 nm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.5 THz) for future 100 Gbit/s PON. It allows the use of distributed feedback lasers at the ONU side. This is rendered possible by generating a frequency comb with carefully chosen free spectral range in a quantum-dash mode-locked laser diode at the optical line terminal. In upstream operation, the frequency comb serves as an LO, whereas the same information is modulated onto all comb lines for the case of downstream. As a result, the ONU laser can drift over the entire comb bandwidth without substantial performance penalty. We experimentally demonstrate downstream and upstream operation with an aggregated raw data rate of 96 Gbit/s, respectively. We further introduce advanced digital signal processing (DSP) methods including a coarse frequency offset compensation (CFOC) and a multiple-input multiple-output (MIMO) equalizer to improve the performance of our concept. We show that the receiver sensitivity can be increased by 3 dB for a high-bandwidth receiver when using a 6 × 2 MIMO equalizer scheme. A 4 × 2 MIMO equalizer scheme enables colorless reception even with a limited-bandwidth receiver.

TDM-PON-Based Optical Access Network for Tactile Internet, 5G, and Beyond

An optical access network plays a critical role in accommodating explosive new services such as augmented reality (AR), virtual reality (VR), machine-to-machine, and human-to-machine interaction applications. Continuous expansion of capacity as well as low latency in the optical access network are very important issues to avoid loss of connectivity for 5G and Tactile Internet. A time-division multiplexing passive optical network (TDM-PON) is an attractive solution to provide optical connectivity to end users in residential, business, and mobile applications since multiple remote nodes with simple optical power splitters give us easy-to-use optical connection anywhere in an optical distributed network. This article reviews TDM-PON-based optical access technologies for bandwidth-intensive as well as low-latency services, and introduces a recent feasibility demonstration of a Tactile Internet testbed. Technical challenges faced by TDM-PON for future networks in terms of capacity, latency, and virtual-izationlslicing are also discussed.

SOA Amplified 100 Gb/s/λ PAM-4 TDM-PON Supporting PR-30 Power Budget with >18 dB Dynamic Range

Semiconductor optical amplifier (SOA) is considered an excellent candidate for power amplification at O-band due to its low cost and small footprint. In passive optical networks (PONs), SOA is popular as a booster and pre-amplifier to improve the link power budget. However, whether as a booster or pre-amplifier, SOA will induce different degrees of nonlinearity when the output power is high, which degrades the transmission performance of the system and leads to a limited receiver dynamic range. In this paper, we experimentally demonstrate the feasibility of using SOA in both transmitter and receiver sides for power budget improvement in 100 Gb/s/λ four-level pulsed amplitude modulation (PAM-4) time division multiplexed PON (TDM-PON) system at O-band. For compensating the linear and nonlinear impairments induced by transceivers and SOA, a look-up-table (LUT) pre-compensation at the optical line terminal (OLT) side and a simple feed-forward equalizer (FFE) at the optical network unit (ONU) side are adopted for downstream transmission. For upstream transmission, a 2nd-order Volterra nonlinear equalizer (VNLE) is utilized at the OLT side, and no pre-compensation is used at the transmitter of the ONU, which releases the digital signal processing (DSP) pressure of ONUs in a multi-user scenario. For the soft-decision FEC (SD-FEC) threshold (1 × 10−2), the IEEE PR-30 power budget requirement is met, and >18 dB dynamic range is achieved in both 25 km downstream and upstream transmission.

A Novel Dynamic Bandwidth Allocation Scheme for XGPON based Mobile Fronthaul for Small Cell CRAN

Time division multiplexing passive optical networks (TDM-PON) have emerged as a promising technology for mobile fronthaul for small cell CRAN. The performance of such TDM-based PON mobile fronthaul for small cell CRAN greatly depends on efficient dynamic bandwidth allocation (DBA) mechanisms. In this paper, a novel DBA mechanism based on the concept of dynamic service interval for ITU-based TDM-PON (XG-PON) for mobile fronthaul has been proposed. The proposed scheme is implemented using network simulator −3 (NS-3) simulation tool for evaluation of network performance parameters. The performance evaluation of the proposed DBA against the existing schemes such as optimized round robin (ORR) and Group-GIANT DBA shows a significant improvement in upstream mean delay, packet loss ratio and grant-request ratio. In addition to this, the proposed scheme shows that larger number of ONU(RRH) can be supported by the network for front haul uplink traffic transmitted via XG-PON in small cell CRAN.

Low Latency DWBA Scheme for Mini-Slot Based 5G new Radio in a Fixed and Mobile Converged TWDM-PON

Cooperative dynamic bandwidth allocation (CO-DBA) enables time division multiplexed passive optical network (TDM-PON) to become a possible solution for mobile fronthaul. Meanwhile, status-report DBA (SR-DBA) still retains its advantage on bandwidth efficiency for conventional PON services. The collaboration of CO- and SR-DBA is an enabling approach for fixed-mobile convergence into a single PON infrastructure. However, a resource allocation conflict between CO- and SR-DBA is to arise when using an emerging 5G new radio interface based on the mini-slot. This conflict will cause a large delay that can not meet the time-sensitive fronthaul requirement. In this study, we consider a time and wavelength multiplexed PON (TWDM-PON) for fixed and mobile services accommodation because of its capacity and flexibility. A novel DWBA scheme is proposed by means of wavelength and bandwidth preemption (WBP) mechanism. The basic rule of WBP is that a time-sensitive traffic can preempt the wavelength and bandwidth allocated to the time-tolerent traffic when a conflict happens. We demonstrate that the proposed DWBA can significantly reduce the latency caused by the conflict, when compared to the existing integrated CO- and SR-DWBA approach with 5G NR mini-slot.

URLLC service-oriented reliable network deployment over MEC enabled TDM-PON based cloud radio access network

New emerging ultra-reliable and low latency communications (URLLC) services have imposed challenged stringent low latency and reliability requirements on fifth generation and beyond (5G/B5G) cloud radio access network (CRAN). However, limited research has been discussed service-oriented reliable network deployment in the mobile edge computing (MEC)-enabled time-division multiplexing-passive optical network (TDM-PON) based CRAN. Moreover, different from most previous protection studies, both optical transport and functional processing resources in multiple domains should be considered in the network deployment of a converged network. To mitigate these limitation, we present a mixed integer linear programming (MILP) for URLLC service-oriented reliable network deployment under the physical and management constraints in MEC-enabled TDM-PON based CRAN. Given the model’s complexity, a heuristic algorithm called “Time-efficient completely isolated protection scheme (TECIPS)” is proposed, which can completely guarantee protection through establishing both primary network topology and strong isolated backup network topology against multiple network failures, while reducing redundant transmission latency and backup recovery latency for URLLC services. Simulation results indicate that our proposed algorithm significantly reduces total latency compared to the benchmark algorithm and receives the near-optimal solution of MILP in both sparse and dense networks with an acceptable time complexity. In addition, the impact of key parameters on the consumption of total transmission latency and backup recovery latency is also evaluated.

Performance of high scalability hybrid system of 10G-TDM-OCDMA-PON based on 2D-SWZCC code

Abstract A new architecture for increasing the number of simultaneous users in a hybrid system and providing a solution for the channel bottleneck problem has been designed and simulated. The 10G-TDM-OCDMA-PON system combines optical code division multiple access (OCDMA) and time-division multiplexed passive optical network (TDM-PON) techniques. The high bit rate TDM-PON system is based on a bit interleaving that uses noncontiguous order for data arranging manner, this system used to obtain ultra-high-speed data rate of 40 Gbps based on four TDM channels of 10 Gbps. The OCDMA system is based on two-dimensional single weight zero cross-correlation (2D-SWZCC) employing polarization and wavelength scheme with two orthogonal polarization angles (vertical and horizontal states). The proposed hybrid system increases the scalability by multiplexing M OCDMA codes in the same time slot of the TDM system that has N time slots. The results show that the proposed system with 2D-SWZCC has better performance with a high number of users and higher scalability than the system with 1D-SWZCC.

PON going beyond FTTH [Invited Tutorial

Time division multiplexing passive optical networks (TDM-PONs) are the most widely deployed optical system solutions in current broadband access networks worldwide. The energy and cost efficiency of both their implementation and operation has reached levels that also make them an attractive option for other cost sensitive communication networks. We discuss how essential features of current TDM-PON specifications can be leveraged to also use them for low latency and high capacity professional services in public and private networks. Also, possible PON architecture evolutions towards added intra-PON communication are outlined that are motivated by the latency requirements of some practical use cases.

Learning EPON delay models from data: a machine learning approach

There have been a large number of studies focused on the characterization of the upstream delay in time-division multiplexing passive optical networks (TDM-PONs). However, most of them focus on finding equations for the average delay and ignore other useful metrics like delay percentiles, which are of paramount interest in dimensioning PONs with delay guarantees. This work shows how to learn delay models from data using supervised machine learning (ML) techniques. Essentially, a nonlinear regression ML algorithm is trained with PON simulation data, showing that it can provide accurate equations for such metrics of interest. In particular, we obtain an R 2 score above 80% under Poisson traffic and above 65% under self-similar traffic, and we provide a general equation for any delay percentile in the upstream channel of a PON employing interleaved polling with adaptive cycle time. We further show its applicability in dimensioning Tactile Internet and 5G transport support scenarios.

Temperature-Robust Monitoring of TDM-PONs Through Optical Coding Assisted by Broadband $\lambda$-Tunable I-OFDR

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 ≥ 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 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> .

Efficient preamble design and digital signal processing in upstream burst-mode detection of 100G TDM coherent-PON

Coherent optics has been proved to be a promising candidate for 100 Gb/s and even beyond single-wavelength time-division multiplexing passive optical networks (TDM-PONs). However, one of the key issues in TDM coherent-PON is how to efficiently and robustly achieve upstream burst-mode coherent detection. To solve this problem, we proposed and demonstrated a reliable and efficient preamble design with corresponding burst-mode digital signal processing (DSP) for coherent upstream burst-mode detection in TDM coherent-PON. To reduce the preamble length, a special designed preamble unit is used for three burst-mode DSP functions including frame synchronization, state-of-the polarization estimation, and frequency-offset estimation. The efficiency of the designed preamble and the overall performances under different test conditions are experimentally verified. We also confirmed the robust performance in large frequency offset, residual fiber dispersion, and long-time running. As a proof-of-concept, we demonstrate the coherent upstream burst-mode detection of 100-Gb/s polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) signals based on a 71.68-ns preamble and corresponding burst-mode DSP, achieving a 36-dB power budget after 50-km single-mode fiber transmission. Around 20-dB dynamic range of received power is also experimentally verified for burst signals in the 100 Gb/s/ λ TDM coherent-PON.

High-speed and long-reach PON employing PM-DQPSK signal and coherent receiver

Abstract The development of communication technology requires a new type of passive optical network (PON) architecture. The architecture needs to be based on time division multiplexing (TDM) of 40 Gbit/s downstream and 10 Gbit/s upstream, and it can realize TDM PON prototype. The PON system achieved the system distance of 120 km supporting 128 ONU with power budget of 53.5 dB via polarization multiplexing differential quadrature phase shift keying format signal which employs the coherent receiver and the digital signal processing.