Time-division Multiplexing Passive Optical Network Research Articles

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.

Redesigned TDM-PON System Architecture Based on Point-to-Point Ethernet Transmission and Software Processing With General-Purpose Hardware

This article proposes a novel architecture of a time division multiplexing passive optical network (TDM-PON) system with general-purpose hardware. The system operates with the point-to-point (P2P) Ethernet protocol and software processing. The architecture is redesigned from the ground up, differing from conventional PON system architectures. In recent years, researchers have attempted to softwarize a number of PON functions such as media access control (MAC) and physical functions, which run on a general-purpose central processing unit (CPU). On the other hand, these existing systems still required PON-dedicated or programmable hardware for processing the PON specific protocol. This paper proposes a TDM-PON system that requires only general-purpose hardware; a network interface card with the use of the P2P Ethernet protocol and a general-purpose server with the use of software processing. To operate the proposed system, we newly developed burst-mode operation and multipoint MAC control schemes, while taking Link Fault Signaling and CPU processing jitter into account. We quantitatively evaluated the burst-mode transmission with P2P generic Ethernet TRx as a preliminary experiment, which showed that T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> were 75 μs and less than 1 μs, respectively. Then, we measured our developed prototype system's performance for verifying the feasibility of our proposal. In specific, it achieved a 5.2 Gbps PON system consisting of an optical line terminal (OLT) server and two optical network unit (ONU) servers under the condition of a 500-ms grant cycle including a 100-ms discovery window.

Optical Power Budget of 25+ Gbps IM/DD PON with Digital Signal Post-Equalization

While infrastructure providers are expanding their portfolio to offer sustainable solutions for beyond 10 Gbps in the access segment of optical networks, we experimentally compare several modulation format alternatives for future passive optical networks (PONs) aiming to deliver 25+ Gbps net-rates. As promising candidates, we consider the intensity modulation direct detection (IM/DD) schemes such as electrical duobinary (EDB) and 4-level and 8-level pulse amplitude modulations (PAM-4/8). They are more spectrally efficient than the conventional non-return-to-zero on-off-keying (NRZ-OOK) used in current 10G PONs. As we move to higher rates, digital equalization enhances the performance by smoothening the systems imperfection. However, the impact that such equalization has on the optical power budget remains unclear. Therefore, in this article, we fairly compare the optical power budget values of a time division multiplexed PON (TDM-PON) exploiting a linear digital signal equalization at the receiver side. We consider the conventional PON configuration (20 km of single-mode fiber (SMF), 1:N optical power splitting) with IM/DD and net-rates above 25 Gbps. Furthermore, we focus on a downstream transmission imposing the bandwidth limitations of 10G components using a digital filter before the detection. The obtained results show that the use of a digital post-equalization with 43 feed-forward (FF) and 21 feedback (FB) taps can significantly improve the signal quality enabling new alternatives and enhancing the optical power budget.

The performance comparison of hybrid WDM/TDM, TDM and WDM PONs with 128 ONUs

Abstract Here, we have simulated different unidirectional passive optical networks (PONs) technologies such as wavelength division multiplexing (WDM), time-division multiplexing (TDM) and hybridPONs with different users for varying fiber length, data rate, continuous wave laser power and number of users. Their performances based on the quality-factor (Q-factor) and bit error rate (BER) using OptiSystem software 7.0 with using an Erbium doped-fiber amplifier (EDFA) were compared. Our model used 16 and 128 users, where the performance of the unidirectional Hybrid WDM/TDM PONs with 4 wavelengths and 128 user systems have better high Q-factor and lower BER, compared to that of 128 user WDM PON and 128 user TDM PON systems.

From 25 Gb/s to 50 Gb/s TDM PON: transceiver architectures, their performance, standardization aspects, and cost modeling

Standardization activities are nearly complete for single wavelength 25 Gb/s time-division multiplexed (TDM) passive optical networks (PONs) and well underway for 50 Gb/s TDM PONs. There is considerable debate in the industry about which technology will be the “next step” after 10 Gb/s TDM PON, now finally starting to ramp up to mass deployment. 50 Gb/s PON clearly brings a 2 × bandwidth advantage over 25 Gb/s, at least in the downstream direction. On the other hand, the increase of speed to 50 Gb/s brings with it a substantial receiver sensitivity penalty of at least 4 dB, which has a chain effect on transceiver architecture, cost, and time-to-market. In this paper, each of those elements is investigated, quantified, and compared to 25 Gb/s.

Lattice based EPON energy-saving scheme analysis

• The state of the art of PON energy saving is discussed. • The lattice theory and fixed point are used to solve the sleep and doze duration time. • We examined the QoS performance based on different simulation scenarios. • We compared our results with the architecture without energy-saving mechanism. Time-division multiplexing passive optical network (TDM-PON) is referred to as a green network because it consumes minimum energy compared to the other access networks technologies. The optical network unit (ONU) mainly chooses to adjust energy-saving in TDM-PON by turning off its receiver and/or transmitter for the substantial time that is called doze or sleep mode respectively. The main challenge in the TDM-PON energy-saving is finding acceptable sleep/doze duration time to achieve energy-saving and guarantee the quality of service (QoS). This paper proposes a mathematical model built based on the lattice theory, which is applied to the results of the fixed-point theory. In the domain of nonlinear systems, each monotone function on a chosen complete lattice has a fixed point, and this point can be interpreted as the solution of the system. The output of the mathematical model is the sleep/doze duration domain that satisfies all requirements and guarantees the QoS metrics. The mathematical model is adopted with doze mode conditions to evaluate the system. Simulation results approve our model that achieves energy-saving up to 63% while keeping the QoS parameters in the acceptable boundary.

DSP enabled next generation 50G TDM-PON

With 10G time division multiplexed passive optical network (TDM-PON) systems ready for massive deployment worldwide, the next generation PON standards are being intensively discussed in both IEEE and ITU-T. Compared with the IEEE’s wavelength stacked 2 ∗ 25 G solution, the ITU-T’s single carrier non-return-to-zero-based 50G TDM-PON has the advantages of low cost, easy operation, and convenient management. However, the 50G TDM-PON will also have to face great challenges in real-world operating conditions. In this paper, we will illustrate the unique role for digital signal processing (DSP) in solving the challenges for the next generation 50G TDM-PON systems, such as device bandwidth limitation, dispersion induced power penalty, and high link budget. To analyze DSP’s feasibility in this application, potential issues such as cost and interoperability are analyzed. Through offline experiments and prototype demonstrations, DSP’s role in enabling next generation single carrier 50G TDM-PON is highlighted.

Performance Analysis of High Speed Bit-Interleaving Time-Division Multiplexing Passive Optical Networks (TDM-PONs)

Time-division multiplexing passive optical networks (TDM-PONs) considered as a good solution for a high bit rate and flexible bandwidth system. In this paper, the simulation of a new bit-interleaving TDM transmitter has carried out. The proposed scheme of downstream TDM-PON based on single Mach–Zehnder modulators (MZM) and single laser diode to carry an electrical multiplexed data providing cost effective, high-transmitted power and easy implementation system. The TDM-PON technique has seen widespread since the beginning of this century, especially with FTTH where flexible bandwidth and high bit rate are required. Hence, the simulation of 10, 25, 40, and 50 Gbps TDM-PON have been presented in three scenarios based on two downstream transmitter schemes of FTTH. Those scenarios have carried out the standard single-mode fiber (SSMF) and the free-space optic (FSO) as transmission media, and the single mode dispersion compensating fiber (DCF) and Fiber Bragg Gratings (FBG) as dispersion compensators. The results show that the electrical multiplexed scheme of TDM transmitter provides better performance with the comparison of the traditional optical TDM transmitter in different scenarios with different bit rates.

Two-stage optimization of uplink forwarding order with cooperative DBA to accommodate a TDM-PON-based fronthaul link

A fronthaul (FH) link based on a time-division multiplexing passive optical network (TDM-PON) has received attention because it is highly cost effective. The uplink transmission has a long forwarding delay in the TDM-PON link, but this issue can be overcome using a cooperative dynamic bandwidth allocation (CO-DBA) scheme. An optical line terminal receives wireless scheduling information from the distributed unit, which is a part of the mobile base station, and can estimate the amount and arrival timing of the FH signal to an optical network unit (ONU) in advance. However, reports of conventional CO-DBA have not considered a situation involving the accommodation of a large number of ONUs, for which forwarding order control considering the FH characteristics is important. By focusing on maintaining the mobile coverage area as a design criterion, this study proposes a two-step maximization scheme of the number of transmittable ONUs within the FH requirement. Numerical simulation indicates improvements in the number of transmittable ONUs and bandwidth usage efficiency.

METAhaul framework of HPON for smart city access networks

ABSTRACTThis work presents, a novel, Mobile Evaluation Transport Architecture haul (METAhaul) of Hybrid PON (HPON), that integrates mobile backhaul (MBH), mobile fronthaul (MFH) and smart devices in one platform. It forms a unified analytical framework, that comprehensively accounts for both fiber/copper (FiCo) and METAhaul broadband access networking technologies, to accommodate the fifth generation (5G) Radio Access Network (RAN) evolution and smart sensor devices. Our framework is flexibly designed to roll out while adopting 5G into the smart city. HPON allows the coexistence of the Time Division Multiplexing Passive Optical Network (TDM-PON), Wavelength Division Multiplexing Passive Optical Network (WDM-PON), hybrid Time-Wavelength Division Multiplexing Passive Optical Network (TWDM-PON), multi-gigabit fast access to subscriber terminals (G.mgfast), and Radio over Fiber (RoF) architecture. It can reduce the power consumption by 78.13%, 79.62% at Sub-6GHz, and 77.7%, 79.21% at mmWave against Optical Transport Network (OTN) and Carrier Ethernet (CE), respectively. Specifically, HPON grants a higher Energy Efficiency Rating (EER) of 65.58%, 67.34% when compared to OTN, and CE each while deploying 15 Radio Units (RU). The proposed next-generation PON architecture can benefit the design and operation of smart city access networks, with its large capacity, multilevel of service, and energy saving.

Joint Optimization of Latency and Deployment Cost Over TDM-PON Based MEC-Enabled Cloud Radio Access Networks

The convergence of optical and wireless networks, and the marginalization of centralized data centers are required for next-generation telecommunications. According to the operators' concern of cost-efficient deployment combined with latency-sensitive requirements, network planning will lay a foundation for the development of next-generation networks. In particular, the network planning of mobile edge computing (MEC)-enabled cloud radio access networks (C-RAN) in a cost-effective and low-latency manner becomes exceedingly challenging. However, most research studies focus on the cost-effective deployment of C-RAN without considering the optimal placement of MEC servers simultaneously. Moreover, deployment costs and access latency will be directly affected by the optimal deployment of both the MEC servers and access networks. Therefore, we investigate how to coordinate the optimal deployment of MEC servers and C-RAN for latency-sensitive services. In detail, a MILP model is proposed to minimize the joint cost of latency and network deployment of time division multiplexing-passive optical network (TDM-PON) based MEC-enabled C-RAN. Given the model's complexity, a heuristic algorithm is also proposed to solve the mixed integer linear programming (MILP) model. Simulations are conducted to evaluate the performance comparisons of different approaches under different network scenarios. The impacts of some key parameters on comparisons of different approaches are also analyzed.

Dynamic bandwidth allocation scheme for network-slicing-based TDM-PON toward the beyond-5G era

In the coming 5G mobile communications era, a huge number of wireless access points will be densely deployed for networks such as mobile fronthaul and Internet-of-Things networks. A network-slicing-based time-division-multiplexing passive optical network (TDM-PON) is one solution for cost-effectively accommodating these access points. It enables us to converge these multiple networks that have different requirements by virtually isolating each sub-network on a single TDM-PON. To achieve this TDM-PON convergence, we propose a dynamic bandwidth allocation scheme that performs uplink bandwidth allocations in a different manner at every sub-network in order to simultaneously satisfy each sub-network requirement. Experiments show that the scheme can simultaneously provide low-latency transmission, bandwidth guarantee, and an auto-discovery process.

SOA Pre-Amplified 100 Gb/s/λ PAM-4 TDM-PON Downstream Transmission Using 10 Gbps O-Band Transmitters

We experimentally demonstrate the downstream transmission of a 100 Gb/s/λ time division multiplexed passive optical network (TDM-PON) based on four-level pulsed amplitude modulation (PAM-4) in the O-band using 10 Gbps transmitters with semiconductor optical amplifier (SOA) and digital signal processing (DSP) at the receiver. Considering the soft-decision FEC (SD-FEC) threshold (1 × 10−2), power budget of 30.3 dB and 29.3 dB have been achieved after 22 km and 50 km fiber transmission, respectively. There is no observable dispersion penalty after 22 km and 50 km transmission. The possibility of 100 Gb/s/λ PON is first investigated using intensity modulation and direct detection (IM/DD) schemes rather than coherent detection schemes.

Nyquist four-level pulse amplitude modulation scheme (PAM-4) based on hierarchical modulation in IM/DD-TDM PON with hybrid equalization

In order to achieve higher power margin in the intensity-modulation and direct detection (IM/DD) based time division multiplexed passive optical network (TDM-PON) system, at the optical line terminal (OLT) side, we propose to use a Nyquist pulse shaped four-level pulse amplitude modulation (PAM-4) by using the electric low pass filter(LPF). In addition, we apply the hierarchical modulation (HM) scheme by assigning of most-significant bits (MSBs) and the less-significant bits (LSBs) of the PAM-4 symbol to optical network units (ONUs) located at different link positions. In addition, an overlap frequency domain equalizer (OFDE) and a vestigial-side band (VSB) filter are used to mitigate the linear inter symbol interference (ISI) and power fading (both of which are incurred by chromatic dispersion (CD)), respectively. The system performance, i.e., bit error rate (BER) and receiver sensitivity for both MSB and LSB, are analyzed by varying different system configurations. Simulation results show that increasing the hierarchical power ratio, which determines the significance difference between the points in the Nyquist pulse shaped HM PAM-4 constellation diagram, can increase the MSB’s receiver sensitivity and reduce the LSB’s receiver sensitivity. Furthermore, it has been demonstrated that the electric low pass filter can reduce the system ISI. In addition, the effect of linear ISI and power fading can be migrated by utilizing OFDE and VSB filter, respectively.

Fiber fault detection based on communication signal

This paper presents a practical method of detecting the fault point of optical fiber link based on the communication signal itself in optical network. The method collects the reference signal and the echo signal with the fault point information through the data acquisition device, and then uses the permutation entropy to extract the random part from the communication signals. Finally, the accurate measurement of the fault point of fiber link is detected by correlation operation. The experiment uses the communication signal transmitted in the time-division multiplexing passive optical network as the detection signal, and the detection object is G652 single-mode fiber with simulated fault point. Different from the traditional optical time-domain reflectometry, the proposed method can measure the fault point of the fiber link without disconnecting the normal communication network, achieve a position resolution of 15 cm, and reduce the measurement cost for the fiber link fault detection.

Demonstration of symmetrical 50-Gb/s TDM-PON in O-band supporting over 33-dB link budget with OLT-side amplification.

Single wavelength 50 Gb/s passive optical network (PON) is an excellent candidate for meeting high capacity requirements. In this paper, we experimentally investigate a symmetrical 50 Gb/s time division multiplexed passive optical network (TDM-PON) system in the O-band based on 25G optics. Semiconductor optical amplifier (SOA) is used in optical line terminal (OLT) side to improve link power budget. We initially investigate the performances of SOA as a booster amplifier with different gain in the downstream and make a trade-off between receiver sensitivity and power budget. The performances of 50 Gb/s non-return-to-zero (NRZ) in the downstream with avalanche photodiode (APD) receiver and upstream with SOA-PIN receiver with different equalization schemes are evaluated. Experimental results show that up to 34.97 dB link power budget is achieved in the downstream direction with 7-tap feed forward equalization (FFE), and 33.76 dB link power budget is achieved in the upstream direction with only 3-tap FFE filtering.

A 50 Gbit/s PAM-4 Linear Burst-Mode Transimpedance Amplifier

This letter presents a linear burst-mode transimpedance amplifier (LBMTIA) capable of receiving 50 Gbit/s 4-level pulse amplitude modulation (PAM-4), targeting upstream transmission in high-rate time division multiplexed passive optical networks (TDM-PONs). Using a digitally controlled high-speed datapath, where offset- and gain are corrected using a fast lookup from on-chip stored settings, the receiver achieves a settling time of 48 ns and has an input dynamic range of at least 17.7 dB for 25 Gbit/s non-return-to-zero (NRZ) and 10.9 dB for 50 Gbit/s PAM-4 at the low-density-parity-check (LDPC) forward-error-control (FEC) threshold of $1\times 10^{-2}$ (as now standardized for 25 and 50G TDM-PONs). The LBMTIA is fabricated in the 0.25 um SiGe:C BiCMOS-technology from NXP and consumes 375 mW.

Network Solutions for CoMP Coordinated Scheduling

Demanding throughput, latency and scalability requirements of 5G networks may be addressed by relying on dense deployments of small cells. Coordinated Multipoint (CoMP) Coordinated Scheduling (CS) techniques are introduced to reduce inter-cell interference in case of dense deployment, given that local CoMP-CS information from the evolved NodeBs (eNodeBs) in the cluster are timely collected at the scheduling decision entity. This work studies how the distribution of CoMP-CS cell information is affected by the backhaul infrastructure in terms of both physical and logical topology. The differentiation between physical and logical infrastructure is justified in the context of new approaches like Software Defined Networking and Network Function Virtualization that enable the dynamic configuration of the network. We consider either a Packet Switched Network with three possible topologies (namely, ring, mesh and star) or a Time Division Multiplexing Passive Optical Network (TDM-PON), both carrying heterogeneous traffic. To improve the convergence time in the TDM-PON, we propose a novel bandwidth allocation scheme to prioritize the signaling traffic with respect to data traffic. Performance of both distributed and centralized CoMP-CS are compared in terms of convergence delay and traffic overhead. Finally, we analyze the impact of the periodicity of CS operations on mobile performance, in terms of average UEs throughput, in the presence of different cell loads.

Predictive Bandwidth Allocation Scheme With Traffic Pattern and Fluctuation Tracking for TDM-PON-Based Mobile Fronthaul

In future radio access systems, since the number of mobile base stations will increase to cope with the increasing mobile traffic, the number of mobile fronthaul (MFH) links will also have to increase. To reduce the MFH link cost, MFH networking has been attracting attention. In particular, the use of a time-division multiplexed passive optical network (TDM-PON) makes the MFH link cost effective. On the other hand, a TDM-PON has a huge latency when forwarding uplink traffic. In a typical dynamic bandwidth allocation (DBA) scheme, an optical network unit (ONU) has a very long transmission waiting time, e.g., several milliseconds. This transmission waiting time in the ONU is a critical problem since the latency requirement for the MFH link is very strict, e.g., less than 250 μs defined by the Third Generation Partnership Project. In this paper, we propose a novel statistical DBA scheme taking high-speed traffic fluctuation to reduce the transmission waiting time. Our proposed scheme allocates bandwidth based on the only ratio of the data amount of each distributed unit and detects the pattern of the transmission interval of the burst signal. We show the feasibility with a numerical simulation and experiments.

Burst-Mode Digital Signal Processing That Pre-Calculates FIR Filter Coefficients for Digital Coherent PON Upstream

This paper proposes a burst-mode digital signal processing architecture for digital coherent time-divisionmultiplexed passive optical network (PON) upstream transmission, wherein two key advances are introduced to shorten the preamble length of burst signals required to complete adaptive equalization, as performed by a constant modulus algorithm: tap coefficients of a finite impulse response (FIR) filter are pre-calculated in the optical network unit (ONU) discovery process, and the feed-forward state of polarization compensation is employed before adaptive equalization. The bit error rate performance attained by the proposal is experimentally evaluated; successful burstmode coherent detection with a high sensitivity of -44.7 dBm is demonstrated for 20 Gbit/s single polarizationquadrature phase shift keying burst signals transmitted over a 40 km single mode fiber, even with the use of a short preamble of 1.3 μs, which meets the optical power specifications required for a 512-way split system. The proposal utilizes register request signals whose preamble is longer than those used in current PON systems to optimize the tap coefficients of the FIR filter, which may disrupt smooth ONU registration in high-splitting-ratio systems. To evaluate this impact, numerical calculations based on the Monte Carlo method are conducted, and the results show that the time required to complete the registration of 512 ONUs is just 40 s or so.