Long-reach Passive Optical Networks Research Articles

A PID-based algorithm to guarantee QoS delay requirements in LR-PONs

In this paper a novel algorithm with delay guarantees for high priority traffic based on a Proportional (P) controller for Long-Reach Passive Optical Networks (LR-PONs) is proposed. We have recently demonstrated that Proportional–Integral–Derivative (PID) controllers are quite effective when controlling guaranteed bandwidth levels and in this paper this functionality is adapted to jointly deal with Class of Service (CoS) and client differentiation in order to fulfill delay requirements. Therefore, it leads to an efficient control of the mean packet delay which enhances the provided Quality of Service (QoS) inside the LR-PON. Simulation results have exhibited that the bandwidth allocation process made by the P controller achieves this objective faster than other existing proposals. In fact, it stabilizes the priority delays in less than 2min comparing with 5 or 6min obtained by other proposals. Furthermore, it has been demonstrated that its performance is more robust than other proposals since it is independent of the initial network conditions, adapting very efficiently the available resources in order to comply with the established delay bounds of the most restrictive services.

可生存LR-PON中基于连接可用性的成本有效规划方法

可生存LR-PON中基于连接可用性的成本有效规划方法

Optimization of Survivable Mesh Long-Reach Hybrid WDM-TDM PONs

Long-reach hybrid wavelength-division multiplexing (WDM) and time-division multiplexing (TDM) passive optical networks (PONs) allow deploying access networks for remote service areas with thousands of customers. Typically, several long fiber cables are run between the central office (CO) of the service provider and each service area in order to feed the service area with data flows. In the service area, array waveguide gratings (AWGs) multiplex and demultiplex wavelengths; then, splitters split wavelengths in order to serve multiple optical network units. This paper proposes use of a mesh topology in service areas, i.e., AWGs can feed each other. This architecture has two main advantages. First, mesh linkages between AWGs make the network structure more robust with a high possibility of integrating survivable schemes. Second, fewer fibers are required between the CO and service areas, leading to a reduction of total length of fiber deployment, with a corresponding reduction of fiber installation and maintenance costs. We support this proposal by showing that i) the proposed architecture is feasible with some modification/combination of conventional PON devices, and ii) while using our optimal and heuristic algorithms for designing survivable long-reach hybrid WDM-TDM PONs, most of these PONs should use the mesh topology in order to minimize the total length of fiber deployment.

Real-Time Optical OFDM Long-Reach PON System Over 100 km SSMF Using a Directly Modulated DFB Laser

A real-time base-band orthogonal frequency division multiplexing (OFDM) transceiver with a simple symbol synchronization and channel estimation scheme is implemented on only one off-the-shelf commercial field programmable gate array (FPGA). The real-time optical OFDM long-reach passive optical network (PON) system with direct detection over 100 km standard single-mode fiber (SSMF) employing a cost-effective directly modulated distributed feedback (DFB) laser has been successfully demonstrated experimentally. The experimental results show that the simplified symbol synchronization with low complexity and high accuracy is effective for long-reach optical OFDM transmission systems. After 100 km SSMF transmission, the power penalty at a bit-error rate of 1e-3 is only about 1.1 dB.

Gain-switched multicarrier transmitter in a long-reach UDWDM PON with a digital coherent receiver

The authors report on the downlink performance of a 10 Gb/s long-reach and ultra-dense wavelength-division multiplexed passive optical network, based on a multicarrier transmitter realized by using an externally injected gain-switched distributed-feedback laser diode. Each of the comb channels, spaced by 10 GHz, is modulated with a 3 Gbaud dual polarization quadrature phase shift keying signal that included a 20% overhead for forward error correction. Frequency selectivity and enhanced receiver sensitivity is achieved by employing a digital coherent receiver to receive the signal. Experimental results achieved in a back-to-back and 100 km transmission scenarios show an excellent worst case receiver sensitivity of -44 dBm.

An experimental demonstration for carrier reused bidirectional PON system with adaptive modulation DDO-OFDM downstream and QPSK upstream signals

A light source centralized bidirectional passive optical network (PON) system based on multiband direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) downstream and quadrature phase-shift keying (QPSK) upstream is experimentally demonstrated. By introducing a simple optical single-side band (SSB) filter at the optical network unit (ONU), all the desired signal bands will be immune from the deleterious signal-signal beating interference (SSBI) noise with only single-end direct-detection scheme. An adaptive modulation configuration is employed to enhance the entire downstream throughput which results in a 150-Gbps downstream data rate with a single optical carrier. In the upstream direction, by recycling the clean downstream optical carrier, a 12.5 Gb/s QPSK format with coherent receiving mechanism in central office is adopted for better receiving sensitivity and dispersion tolerance. With the power enhancement by the long-reach PON architecture, the downstream splitting ratio can achieve as high as 1:1024.

Direct-detection optical OFDM superchannel for long-reach PON using pilot regeneration

We demonstrate a novel long-reach PON downstream scheme based on the regenerated pilot assisted direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) superchannel transmission. We use the optical comb source to form DDO-OFDM superchannel, and reserve the center carrier as a seed pilot. The seed pilot is further tracked and reused to generate multiple optical carriers at the local exchange. Each regenerated pilot carrier is selected to beat with an adjacent OFDM sub-band at ONU, so that the electrical bandwidth limitation can be much released compared to the conventional DDO-OFDM superchannel detection. With the proposed proof-of-concept architecture, we experimentally demonstrated a 116.7 Gb/s superchannel OFDM-PON system with transmission reach of 100 km, and 1:64 splitting ratio. We analyze the impact of carrier-to-sideband power ratio (CSPR) on system performance. The experiment result shows that, 5 dB power margin is still remained at ONU using such technique.

Design of Directly Modulated Long-Reach PONs Reaching 125 km for Provisioning of Hybrid Wired–Wireless Quintuple-Play Service

Design tools for the quintuple-play service provisioning in a long-reach passive optical network (LR-PON) using off-the-shelf directly modulated lasers (DMLs) are experimentally demonstrated. The quintuple-play service including broadband wired Internet, phone/voice data, wireless high-definition TV, wireless data, and home security/control is provided by a radio-over-fiber bundle of multi-format orthogonal frequency division multiplexing (OFDM) signals. This bundle occupies a multi-octave band and consists of a full-standard worldwide-interoperability-for-microwave access signal, a long-term evolution signal, two ultra-wideband channels, and an ad hoc OFDM signal providing gigabit Ethernet connectivity. Dynamic centralized impairment compensation, fixed optical dispersion compensation, proper selection of the multiplexed signal level applied to the DML, and unbalanced power sharing between the different OFDM-based signal formats are shown as effective design tools for the delivery of the quintuple-play service to end-users. The experimental validation confirms that the DMLs are an effective solution to deliver the quintuple-play service to end-users 125 km away from the central office. Additionally, it is shown that the directly modulated LR-PON employing negative residual dispersion is able to provide the quintuple-play service to end-users located between 75 and 125 km away from the central office with an error vector magnitude (EVM) margin, relative to the EVM stated in each signal standard, by more than 1 dB. Therefore, the proposed directly modulated LR-PON is a cost-effective alternative to networks using external modulation for the provision of wireless and wired quintuple-play service to end-users using a single hybrid network.

Low-Latency Polling Schemes for Long-Reach Passive Optical Networks

The increased propagation delay of future long-reach passive optical networks (LR-PONs) may lead to a significantly increased idle time and delay if optical network units (ONUs) use conventional report-grant mechanisms. Sophisticated and efficient bandwidth allocation mechanisms are required to cope with the imposed propagation delay in LR-PONs. In this study, we evaluate three dynamic bandwidth allocation (DBA) frameworks in terms of frame (packet) delay; namely, we consider conventional (interleaved) polling for traditional PON and two recently introduced scheduling paradigms for next generation LR-PON, i.e., multi-thread polling (MT-P) and real-time polling (RT-P). We enhance MT-P and RT-P by applying the just-in-time framework. Next, we provide an analytical framework for evaluating the end-to-end frame delay in our enhanced MT-P and RT-P frameworks. We compare their performance with conventional polling and double-phase polling and investigate their shortcomings and advantages in an LR-PON setting. The simulation results closely match the analysis for this framework. Also, our results indicate that RT-P significantly reduces frame delay in LR-PONs compared to MT-P and conventional polling frameworks.

Study on Electrical Power Distribution Among Coexisting OFDM-Based Wired-Wireless Signals Along Long-Reach Passive Optical Networks

The provision of a quintuple-play service (fixed Internet and telephony, mobile telephony/Internet, security/control applications, and wireless high-definition audio/video distribution) along wavelength division multiplexing long-reach passive optical networks has been proposed recently. Five coexisting orthogonal frequency division multiplexing based signals have been used to deliver the quintuple-play service to each user. In this paper, the electrical power distribution (EPD) among those five coexisting signals is studied using numerical simulation. The need for EPD optimization is stressed, as the optimum EPD (OEPD) enables the maximization of the signal and network performances. The OEPD is achieved by setting optimized gains (OG) in the electrical amplifiers used to impose the electrical power level of each one of the coexisting signals. For practicability, the gains are optimized only for a specific fiber length. For other fiber lengths, the use of those OG may cause performance degradation. This degradation can be mitigated if a predistortion (PD) scheme, which compensates for the frequency-dependent losses (FDLs) of the transmission channel, is used with proper OG. It is shown that the main advantage of using OG + PD over using OG only is to enable the reduction of the performance degradation that occurs for other fiber lengths than the one considered in the OG optimization. The capability to mitigate the FDLs is more limited in the absence of PD. Therefore, the advantage of using OG + PD over OG increases with the magnitude of the variation of the FDLs inside the band of the signals. However, under the conditions considered in this work, the impact of the use of OG + PD on the maximum transmission reach (MTR) is determined to be reduced (less than 1% relative to the MTR obtained with OG only, 126.5 km of standard single-mode fiber).

Planning of survivable long-reach passive optical network (LR-PON) against single shared-risk link group (SRLG) failure

Long-Reach Passive Optical Network (LR-PON) is known as a promising and economical solution for Next-Generation PON (NG-PON). Survivability is one of the key issues in the planning of LR-PON because massive high-rate traffic flows may be interrupted in case of network component failure. However, the survivability issue for LR-PON is addressed in little works. More importantly, most of the previous works focus on single distribution fiber failure and remain untouched the simultaneous failure of multiple distribution fibers, which is a possible failure scenario in LR-PON. In this paper, we focus on the survivability of LR-PON against single Shared-Risk Link Group (SRLG) failure. A reliability model is proposed to represent the disconnection probability of the ONUs. Based on this reliability model, we propose a novel Backup Fibers Protection (BFP) scheme. In the BFP scheme, we deal with the optimization problem of allocating backup capacity and deploying backup fibers. Under the constraint of reliability requirement, our objective is to fully protect all traffic demand in the network with the minimum deployment cost of backup fibers. Both ILP-based approach and heuristic approach are proposed to solve the optimization problem in the BFP scheme. To the best of our knowledge, this paper is the first work regarding the survivability of LR-PON against single SRLG failure. Through extensive simulation, we investigate the performance of BFP and demonstrate its effectiveness in different scenarios.

Performance of Long-Reach Passive Access Networks Using Injection-Locked Fabry–Perot Laser Diodes With Finite Front-Facet Reflectivities

In this study, we use the injection-locked Fabry-Perot laser diodes (FP-LDs) with front-facet reflectivities of 10% and 35% respectively, as colorless optical networking unit (ONU) in long-reach passive optical networks (LR-PONs). Here, the injection-locked FP-LD is directly modulated at 2.5 Gbit/s on-off keying (OOK) and 10 Gbit/s orthogonal-frequency-division-multiplexing (OFDM) modulations for upstream traffic transmission over 60 km of single-mode fiber (SMF). Different operating parameters for the injection-locked FP-LD to achieve higher data rate transmission are reported.

Offline and Online Multi-Thread Polling in Long-Reach PONs: A Critical Evaluation

Multi-thread polling (MTP) with offline scheduling and offline excess bandwidth distribution has recently been proposed to overcome the long propagation delay of long-reach passive optical networks (LR-PONs). In this paper, we propose a complementary MTP approach with online scheduling and online excess bandwidth distribution. We evaluate the throughput-delay performance of offline and online MTP against offline and online single-thread polling (STP) with excess bandwidth distribution as well as double-phase polling (DPP) with excess bandwidth distribution. We find that online MTP and STP as well as DPP give significantly lower average packet delays than offline MTP.

New concept in long-reach PON Planning: BER-aware wavelength allocation

With the use of arrayed-waveguide grating (AWG) and erbium-doped-fiber amplifier (EDFA), the long-reach passive optical network (LR-PON) can provide enormous bandwidth over large distances. However, these new technologies can also deteriorate the receivers' bit-error rate (BER) performance. By bringing the concept of BER-awareness into network planning, we can alleviate the performance deterioration, which could in turn lead to simpler design of receiver and thus lower the total cost of LR-PON.The effects of AWG and EDFA on BER are studied in this paper. An analytical model of BER performance is developed as a function of the output port location in the AWG and the distance of the receiver from the AWG. Not only does the proposed model capture the power loss caused by AWG, but it also accounts for several transmission impairments, including the beat noise due to inter-channel crosstalk in the AWG, the amplified spontaneous emission (ASE) noise related to EDFA, and the thermal noise related to the receiver. Based on this model, we propose both short-term and long-term distance-aware wavelength allocation schemes, which balance the BER among the optical network units (ONUs) at different distance. Simulation results show that average BER improves and the relative standard deviation decreases.

Performance analysis of ONU-wavelength grouping schemes for efficient scheduling in long reach-PONs

Long Reach PONs (LR-PON) were proposed to extend the benefits of Passive Optical Networks (PON) to more users and to a larger area. This paper considers a Dynamic Bandwidth Allocation (DBA) based on a hybrid combination of Time Division Multiplexing (TDM) and Wavelength Division Multiplexing (WDM). The time complexity of the DBA algorithm is typically O(nlogn), where n denotes the number of ONUs. Since the maximum number of supported ONUs in an LR-PON can be as high as 2048, the computation time required for computing a schedule will be very high and directly impacts the overall network performance. In this paper, we have presented a grouping strategy to reduce the computation requirements. The number of ONUs is split into mutually exclusive groups with the OLT scheduling each group independently and in parallel. With the static grouping strategy every user is assigned to a group and the assignment of wavelength resources is fixed. However, with non-uniform loads, we observed that static grouping was not found to be suitable as the delay variation was significant across the groups. To address this gap, we introduce the concept of dynamic grouping and define three dynamic grouping heuristics that adapt to the current network load conditions and (re)allocate the ONUs and wavelength resources suitably. The proposed schemes have been compared in terms of delay variation and wavelength utilization. Of the three heuristics, ONU to Least Loaded wavelength group (OLL) and Least Wavelength Resources (LWR) heuristics balance the packet delay across ONUs assigned to different groups and Proportional Wavelength Usage (PWU) heuristic reduces power consumption by allocating fewer wavelength resources.

A midterm DBA algorithm for quality of service on aggregation layer EPON networks

This work presents a new approach on dynamic bandwidth allocation (DBA) for Ethernet Passive Optical Networks (EPONs). A brief introduction to the DBA area and major term definitions are given. The related research and standardization efforts are presented. Justification that EPONs can be used on the aggregation network is provided, based on their evolution and related research proposals. Focus is given to the Long Reach-Passive Optical Networks (LR-PONs) and their limitations which show the need for a non-polling, midterm DBA scheme for next-generation EPONs. The challenges arising, because of this new approach, are discussed along with possible solutions. Finally, this work proposes the EMDBA algorithm which is able to overcome the discussed issues. The correct operation of this algorithm is confirmed by a set of simulations using OMNet++ framework, and the outcome results show that EMDBA performance is satisfactory in terms of delay and service differentiation.

Scaling the System Capacity and Reach of a 10G-TDM–OCDM-PON System Without an En/Decoder at an ONU

To realize high scaling of a 10-Gbps-class optical access system, we propose and demonstrate two different long-reach hybrid multiplexing passive optical network (PON) systems. First, we demonstrate good scalability in the ultimate transmission distance over 100 km single-mode fiber without dispersion compensation of a 10G wavelength division multiplexing (WDM)-time division multiplexing (TDM)-optical code division multiplexing (OCDM) PON system. Second, we also demonstrate a 100 km 10G/1G-TDM-OCDM-PON system for the purpose of the scalability of the current mixed GE-PON and 10G-EPON system.

Real-time ultra-wideband video streaming in long-reach passive optical networks with wireless radiation in the 10 and 60 GHz Bands

Real-time video streaming using ultra-wideband (UWB) technology is experimentally demonstrated along long-reach passive optical networks (LR-PONs) with different wired and wireless reaches. Experimental tests using external and direct modulation with UWB wireless radiation in the 10- and 60-GHz bands are performed. An ultra-bendable fiber is also considered for a last-mile distribution. The video quality at the output of the optical fiber infrastructure of the LR-PON is assessed using the error vector magnitude (EVM), and the link quality indicator (LQI) is used as a figure of merit after wireless radiation. An EVM below -17 dB is achieved for both externally and directly modulated LR-PONs comprising up to 125 km of optical fiber. EVM improvement is observed for longer LR-PONs when directly modulated lasers (DMLs) are used because of the amplitude gain provided by the combined effect of dispersion and DML's chirp. Compared with optical back-to-back operation, the LQI level degrades to the maximum around 20% for LR-PONs ranging between 75 and 125 km of fiber reach and with a wireless coverage of 2 m in the 10-GHz UWB band. The same level of LQI degradation is observed using the 60-GHz UWB band with a LR-PON integrating 101 km of access network, a last-mile distribution using ultra-bendable fiber, and a 5.2-m wireless link.

Performance comparison of power fading mitigation techniques in multiband OFDM-UWB signals transmission along LR-PONs

The single sideband (SSB) modulation is assessed as a means to mitigate the dispersion-induced power fading on the distribution of ortogonal frequency division multiplexing (OFDM) ultra wideband (UWB) radio signals along long-reach passive optical networks (LR-PONs). Particularly, two different SSB architectures, namely, Sieben's architecture and four phase modulator (FPM) architecture are optimized to provide maximum sideband suppression. The minimum optical signal-to-noise ratio (OSNR) required to simultaneously distribute all the 14 OFDM-UWB sub-bands along the LR-PON distances ranging between 80 and 100 km is also evaluated through numerical simulation. FPM architecture is preferable over Sieben's architecture because the latter SSB architecture generates carriers-carriers beat term at the photodetector output with high power, thereby causing significant degradation in the OFDM-UWB sub-bands with lower central frequencies. The simultaneous distribution of the 14 SSB OFDM-UWB sub-bands in the LR-PON using the FPM architecture shows a minimum OSNR penalty of 3 dB compared with the centralized dispersion compensation technique.

OFDM-WDM LR-PON with ultra-bendable fiber for last-mile distribution of quintuple-play service

The provision of quintuple-play services along wavelength division multiplexed (WDM) long-reach passive optical networks (LR-PONs) employing an ultra-bendable fiber in last-mile distribution is demonstrated experimentally. Particularly, the simultaneous transmission of three 100-GHz-spaced optical channels for the provision of double sideband orthogonal frequency-division multiplexing (OFDM) wireless and wired quintuple-play services to the premises of users located at 75, 85, and 100 km away from the central office is demonstrated. The OFDM-WDM LR-PON is tested considering the last-mile fiber distribution suffering from severe bending conditions without optical dispersion compensation. The experiments are performed for a worst last-mile fiber bending case emulated by considering a Corningr ClearCurver fiber experiencing 20 bends and a bend radius of 7.5 mm. All the OFDM signals received at the premises of users present error vector magnitude (EVM) levels compliant with the EVM thresholds of the corresponding standards. An EVM degradation in the OFDM signals received by each user not exceeding 0.8 dB due to the last-mile distribution fiber is achieved.