Next-generation Passive Optical Network Stage Research Articles

Design of long‐reach symmetric 1.6 Tbps bidirectional NG‐PON2 using 2D spectral/spatial SWZCC code

AbstractIn this paper, a bidirectional symmetric 16 × 10 Gbps next generation passive optical network stage 2 (NG‐PON2) based time and wavelength division multiplexing PON (TWDM‐PON) has been designed. To satisfy the requirement for ever‐increasing demands for high‐security, high speed and long‐reach with high system capacity to handle the large number of users, two‐dimensional spectral/spatial single weight zero‐cross correlation code has been employed in TWDM‐PON. The results show that the proposed design can handle simultaneous users of 240 in downstream and 250 in upstream channels over 10 km transmission distance at symmetric 1.6 Tbps data rate. The transmission distance can be extended upto downlink 110 km and uplink 170 km, delivering receiver sensitivity of −45 and −46 dBm, respectively. Also, high optical signal to noise ratio of 62 dB in downlink and 72 dB in uplink is successfully achieved. Meanwhile, the proposed work is superior to the recent work.

Performance Investigations of Symmetric 80 Gbps TWDM NG-PON2 coexisting with GPON/XG-PON

Abstract In this paper, the system consists of 80 Gbps next-generation passive optical network stage 2 (NG-PON2) co-existing with gigabit passive optical network (GPON) and 10 Gbps gigabit passive optical network (XG-PON) has been presented. The performance of the system has been evaluated for minimum bit error rate (BER) for varied distances (40 km to 100 km). It has been observed that due to the inadequate performance of XG-PON for upstream for higher lengths; the proposed system is limited to 40 km fiber length. To overcome this problem the proposed system is further simulated by increasing upstream transmission power of GPON and XG-PON. With the optimum parameters, the system maximum distance of 60 km has been reached for all GPON, XG-PON, and NG-PON2 without any inline amplification.

A novel bidirectional entirely passive remote node design for ring topology based NG-PON2 with fiber faults protection capability

The service disruptions in passive optical networks (PONs) due to fiber or node failure is an important issue. In the conventional star topology time and wavelength division multiplexing (TWDM) based next generation passive optical network stage 2 (NG-PON2), there is no provision to restore the service if the fiber between remote node (RN) and optical network unit (ONU) fails. In this paper, we proposed a novel entirely passive node design for ring based NG-PON2 which provides fiber fault protection against any fiber break between RNs. The working of the proposed node is verified by simulating normal conditions and fault conditions. It is observed that in the case of fiber failure, the affected ONUs can still communicate with the optical line terminal (OLT). The performance of the system has been analyzed in terms of bit error rate (BER), and the BER <10−9 confirms the correct working of the system.

Entirely passive remote node design and system architecture for bus topology based 80Gbps symmetrical NG-PON2

The next generation passive optical network stage 2 (NG-PON2) is a broadcast network in which a large number of optical network units (ONUs) can be served using various network topologies. In this paper, a purely passive remote node (RN) design based on fiber bragg grating (FBG) is presented for the bus topology of a high split NG-PON2 system. The performance of the proposed node has been analysed for a symmetric 80 Gbps NG-PON2 system serving 1024 ONUs in terms of bit error rate (BER) and optical signal to noise ratio (OSNR). The working of the proposed node has been explained with the optical frequency spectrums for downstream and upstream signals. The observed OSNR levels for the ONUs operating at the 1st RN is 84.8743 dB which decreases to 75.7973 dB for the ONUs connected to the 8th RN. The BER level < 10–9 for both upstream and downstream confirms the correct working of the proposed node in the NG-PON2 system.

Polarization multiplexing and hybrid modulation based bandwidth efficient NG-PON2 coexisting with GPON and XG-PON

Bandwidth efficiency is an important design parameter for next-generation passive optical network stage 2 (NG-PON2). In this paper, two optical line terminal (OLT) designs based on the polarization split state are proposed for NG-PON2. The first method doubles the data rate per wavelength by separate amplitude modulation of both polarization states, whereas, in the second method, differential phase-shift keying (DPSK) modulates another data stream on each amplitude-modulated state; this approach increases the data rate per wavelength fourfold. The proposed system provides NG-PON2 access while coexisting with a gigabit passive optical network (GPON) and 10 GPON (XG-PON). The proposed system design serves 1024 NG-PON2 opitcal network units (ONUs), 128 GPON ONUs, and 128 XG-PON ONUs. The transmission performance of the system is verified by evaluating the bit error rate (BER) for varied received power. An acceptable BER level of less than ${{1}}{{{0}}^{- 9}}$ is considered in this work.

Performance analysis of erbium-doped fiber amplifier (EDFA) and hybrid optical amplifier in NG-PON2 based on TWDM-PON system

One of the milestones in the optical access network evolution is the Next-Generation Passive Optical Network Stage 2 (NG-PON2) that has 40 Gbps as minimum upstream/downstream capacity. The optical amplifiers have to implement to combat the power degradation in the transmission line. This research aims to analyze the performance of EDFA boosters and hybrid optical amplifiers, which are implemented on TWDM-PON systems based on NG-PON2. Our work used 80 Gbps data speed, which each channel had 10 Gbps on eight channels with a channel space of 100 GHz. The optical link used in this simulation was 60 km with the Erbium-Doped Fiber Amplifier (EDFA) and Hybrid Optical Amplifier (HOA). The performance analysis is based on the variation of ONU and amplifier. Based on the results, the best value in the downstream is the transmission line using EDFA with the received power of - 19.184 dBm, Q Factor of 7.975, and BER of 5.852 x 10−16. In upstream transmission, the best value obtained was a hybrid optical amplifier with a received power value of 9.025 dBm, Q Factor of 69.64, and BER of 0. The optical amplifier increased the system performance when implemented on TWDM-PON systems based on NG-PON2.

All-optical encryption in 80-Gbps next-generation passive optical network stage 2

Passive optical network broadcasts extensive data to subscribers. However, they are vulnerable to various security attacks. The main objective of our work is to assess the information security aspects at the physical layer of next-generation passive optical network stage 2 (NG-PON2). Our paper focuses on the security issues faced by NG-PON2, and we propose an encryption method using the all-optical exclusive-OR gate. The proposed simulation architecture of symmetric 80-Gbps NG-PON2 is based on array waveguide grating. Further, we verified the inherent security of the NG-PON2 system through an eavesdropping attempt at an optical network unit (ONU). For this, we used a key exchange mechanism using the Diffie–Hellman algorithm for sharing individual unique keys between every ONU and the optical line terminal. The simulation results show that the presented technique provides secure broadband services in the access network. The transmitted data are encrypted to ensure confidentiality on the multipoint fiber connection. We have evaluated the transmission performance of the proposed set up and achieved acceptable results in terms of Q-factor (7.12 dB) and bit error rate of (5.26 × 10 − 13). The bits in the optical domain, which are sent to the first ONU, are also compared with the received optical bits at the receiving ONU. The correct reception of the bits at the intended ONU and the inability of malicious ONUs to eavesdrop the data of other ONUs validates the scheme.

Performance Analysis of Full-Duplex NG-PON2-RoF System with Non-linear Impairments

The motivation of this study springs from the need of exploiting the advantages of high data rate and increased mobility of the transmitted signal in the Next Generation Passive Optical Network stage 2 (NG-PON2) incorporated into Radio over Fiber (RoF) system. Nonetheless, such system is prone to degradation due to the nonlinear effects, namely, the non-linear impairments. Accordingly, this study suggests a design for a full-duplex NG-PON2-RoF system and it investigates the impact of the nonlinear effects on the performance of system, such as; Self-Phased Modulation (SPM), Cross-Phase Modulation (XPM), and Four-Wave Mixing (FWM). However, these effects would result in a significant data loss in Time and Wavelength Division Multiplexing-Passive Optical Network (TWDM-PON). To achieve the intended purpose of this investigation, both the performance of the suggested system and the nonlinear effects of SPM, XPM, and FWM are measured with reference to the qualitative parameters, such as; Bit Error Rate (BER), Q-Factor, Power link Budget, and the Eye-diagram. The results show that the system performs efficiently; however, in the presence of the nonlinear effects, the performance of the systems degrades significantly affecting the signal quality. It is worth noting that the FWM effect yields the most negative impact followed by the XPM, and the SPM effect yields the least significant impact on the system. Also, the system yields the capacity of transmitting range of 20-100 Km, and it results in data rate of 40-80 Gbps. The proposed system is simulated using the software Optisystem 15.

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

Abstract With reference to huge investment needed for greenfield passive optical network (PON) deployment, it is immensely important to define procedures and algorithms aimed towards optimal layout and network planning to reduce the overall expenditure due to capital expenditure and operational expenditure as much as possible. We propose an integer linear programming (ILP) based optimization model that explores optimal network dimensioning and placement of network equipment at appropriate locations so as to minimize the overall expenditure. Based on the number of users [optical network units (ONUs)], user’s bandwidth demand, power budget, maximum distance from optical line terminal (OLT) to users, available number of wavelengths and OLT ports, and geographical locations of ONUs, OLT and candidate locations of remote nodes (RNs), the model selects the number, type, splitting ratio and locations of passive devices. The RN device type is selected to be either power splitter or array waveguide grating. Optimal PON architecture is appropriately identified to be time division multiplexing or time-and wavelength division multiplexing (TWDM) depending on the requirement. It provides complete interconnection details among all devices, the overall expenditure, the number of OLT ports and the number and associated data rates of wavelengths to be used. We show exhaustive results for two deployment regions (viz. urban and rural) with different number of ONUs and bandwidth demands from users.We also show result with actual locations of OLT, ONUs and RNs selected from Google map. The proposed ILP model has low computational complexity and offers optimal solution within a reasonable time limit, without requiring a heuristic approach that provides a sub-optimal solution. The TWDM-PON conforms to next-generation PON stage 2 (NG-PON2) specifications and can be used as a useful tool for setting up NG-PON2.

Performance analysis and optimization of wavelength routed (WR) and wavelength selected (WS) hybrid optical distributed network (ODN) for next generation passive optical network stage 2 (NG-PON2)

Next-generation passive optical network stage 2 (NG-PON2) supports the wavelength routed optical distributed network (WR-ODN), power splitter optical distributed network or wavelength-selected optical distributed network (WS-ODN) and hybrid of both the architecture configuration. NG-PON2 is world’s first multi-wavelength passive optical network (PON) standard. The fiber dispersion and nonlinearity degrades the performance of NG-PON2 severely. Fiber nonlinearity depends on the optical launch power and fiber reach. This paper focuses on maximizing the network performance and maximizing the number of simultaneous users with error-free performance by optimizing the optical launch power respectively at dynamic reach and differential reach. The optical launch power is optimized to abate the fiber nonlinearity and significantly enhances the performance of NG-PON2 at dynamic fiber reach for Alcatel 6912 Teralight Ultra 1625 commercial fiber specification. Furthermore, precise values of the optimum launch power for the dynamic fiber reach, for different NG-PON2 architecture, under industrial fiber specification is meticulously obtained. It is identified that irrespective of both, WR-ODN and WS-ODN architecture configuration, optimum launch power remains constant. Power budget is calculated for both, maximizing the performance and maximizing the simultaneous number of users at differential reach and dynamic reach of the NG-PON2.

Downstream performance analysis and optimization of the next generation passive optical network stage 2 (NG-PON2)

The increase in the number of users and high end to end demand of massive data-rate directs the attention towards innovative point to multipoint links that satisfy the need for next-generation passive optical network stage 2 (NG-PON2). NG-PON2 architecture has the capability to support power-split and wavelength-split optical distribution network (ODN) as well as a hybrid of two ODNs. Wavelength routing (WR) ODN has adequate low insertion loss than the power splitter (PS) ODN which can fulfill the exponential increase in demand for greater connectivity. The wavelength routing passive optical network (WR-PON) is investigated using the OptiSystem-13 simulation design tool. In this paper, we optimize the downstream transmission of eight channels WR-PON over 60 km and 40 km of standard single mode practical fibers (G.655 and G.652) with 10 Gb/s per channel and compared it with PS-ODN based passive optical network (PON). Both WR-PON and PS-PON are analyzed in detail under the specifications of deployed optical fibers like ITU-T G.652.A fiber, ITU-T G.652.B fiber, Alcatel 6912 Tealight Ultra 1625 fiber, Corning LEAF 1625 fiber, and Lucent True-Wave RS 1625 fiber. Next generation multi-wavelength system performance is limited predominantly due to fiber dispersion and nonlinearities. Fiber nonlinearities and dispersions are mitigated and performance is enhanced by characterizing the system and optimizing optical launch power for both WR-PON and PS-PON. Furthermore, the effect of optical launch power on performance is investigated and evaluated for each practical fiber configuration with common optical modulation formats, return to zero external modulation (RZ-EM) and non-return to zero external modulation (NRZ-EM). Power budget for each configuration is calculated and tabulated.

Traffic-aware energy saving scheme with modularization supporting in TWDM-PON

Abstract Time and wavelength division multiplexed passive optical network (TWDM-PON) is considered to be a primary solution for next-generation passive optical network stage 2 (NG-PON2). Due to the feature of multi-wavelength transmission of TWDM-PON, some of the transmitters/receivers at the optical line terminal (OLT) could be shut down to reduce the energy consumption. Therefore, a novel scheme called traffic-aware energy saving scheme with modularization supporting is proposed. Through establishing the modular energy consumption model of OLT, the wavelength transmitters/receivers at OLT could be switched on or shut down adaptively depending on sensing the status of network traffic load, thus the energy consumption of OLT will be effectively reduced. Furthermore, exploring the technology of optical network unit (ONU) modularization, each module of ONU could be switched to sleep or active mode independently in order to reduce the energy consumption of ONU. Simultaneously, the polling sequence of ONU could be changed dynamically via sensing the packet arrival time. In order to guarantee the delay performance of network traffic, the sub-cycle division strategy is designed to transmit the real-time traffic preferentially. Finally, simulation results verify that the proposed scheme is able to reduce the energy consumption of the network while maintaining the traffic delay performance.

Four-fold increase in users of time-wavelength division multiplexing (TWDM) passive optical network (PON) by delayed optical amplitude modulation (AM) upstream

Abstract In this paper, we have proposed and simulated optical time division multiplexed passive optical network (TDM-PON) using delayed optical amplitude modulation (AM). Eight upstream wavelengths are demonstrated to show optical time wavelength division multiplexed (TWDM) by combining optical network units (ONU) users data at the remote node (RN). Each ONU generates 2.5 Gb/s user data, and it is modulated using novel return to zero (RZ) delayed AM. Optical TDM aggregates 10 Gb/s data per wavelength from four 2.5 Gb/s upstream user data, which facilitates four different ONU data on the same wavelength as 10 Gb/s per upstream wavelength and, simplify the laser requirements (2.5 Gb/s) at each optical network unit (ONU) transmitter. Upstream optical TWDM-PON is investigated for eight wavelengths with wavelength spacing of 100 GHz. Novel optical TDM for upstream increased the number of the simultaneous user to fourfold from conventional TWDM-PON using delayed AM with a high-quality-factor of received signal. Despite performance degradation due to different fiber reach and dispersion compensation technique, Optical TWDM link shows significant improvement regarding receiver sensitivity when compared with common TWDM link. Hence, it offers optimistic thinking to show optical TDM at this phase as one of the future direction, where complex digital signal processing (DSP) and coherent optical communication are frequently demonstrated to serve the access network. Downstream side conventional TWDM eight wavelengths are multiplexed at the OLT and sent downstream to serve distributed tunable ONU receivers through an optical distribution network (ODN). Each downstream wavelengths are modulated at the peak rate of 10 Gb/s using non-return to zero external modulation (NRZ-EM). The proposed architecture is cost efficient and supports high data rates as well as “pay as you grow” network for both service providers and the users perspectives. Users are classified into two categories viz home-user and business-user, with an option for easy up-gradation. Proposed architecture operates on next generation passive optical network stage 2 (NG-PON2) wavelength plan, with symmetrical data rate. Downstream performance is investigated by comparing, high power laser source with a conventional laser source and the L-band Erbium-doped fiber amplifier (EDFA) of gain 10 dB and 20 dB. Downstream eight wavelengths perform error-free up to 40 Km fiber reach and 1024 splitting points. Power budget of the proposed architecture incorporates the N1, N2, E1 and E2 optical path loss class.

Comparison of Bit Error Rate of Line Codes in NG-PON2

This article focuses on simulation and comparison of line codes NRZ (Non Return to Zero), RZ (Return to Zero) and Miller’s code for NG-PON2 (Next-Generation Passive Optical Network Stage 2) using. Our article provides solutions with Q-factor, BER (Bit Error Rate), and bandwidth comparison. Line codes are the most important part of communication over the optical fibre. The main role of these codes is digital signal representation. NG-PON2 networks use optical fibres for communication that is the reason why OptSim v5.2 is used for simulation.

RSOA-Based FDM PON Upstream With Flexible Multiple Access Capabilities in an NG-PON2 Compliant Architecture

In a passive optical network (PON) architecture compliant with the next-generation PON Stage 2 standard layout, the frequency-division multiplexing (FDM) modulation has been exploited to effectively increase the upstream (US) capacity by overcoming the bandwidth limitation of the reflective semiconductor optical amplifiers (RSOAs) used at the optical network unit (ONU). The intrinsic flexibility offered by the FDM modulation allowed us to properly choose the FDM subcarrier assignment, the modulation format, and the baud rate per each ONU. A rate of 2 Gb/s per ONU has been experimentally demonstrated over a 20 km transmission in an optical distribution network (ODN) with 27 dB losses, and a rate of at least 1 Gb/s per ONU has been obtained after a 43 km standard single-mode fiber in an ODN with 31 dB losses. The preliminary experimentation has been carried out by means of two independent RSOA-based ONUs, sharing the same seed, targeting 32 Gb/s capacity per wavelength and 128 Gb/s overall throughput by means of 4 US wavelength division multiplexed carriers.

The transmission of symmetric 40 Gb/s TWDM-based NG-PON2 utilizing delay interferometer (DI) for RSOA bandwidth enhancement

Abstract Time and wavelength-division multiplexed passive optical network (TWDM-PON) has been finally selected as the pragmatic solution for the next-generation passive optical network stage 2 (NG-PON2). In this paper, we propose a symmetric 40 Gb/s TWDM-PON system with low cost reflective semiconductor optical amplifier (RSOA) for both downstream and upstream directions. A single bi-pass delay interferometer (DI), deployed in the optical line terminal (OLT), is used to enhance the poor performance of the RSOA with respect to the low bandwidth induced by laser chirp. With the help of the 40 GHz free spectrum range (FSR) DI, we show a successful transmission of the proposed work through simulation study where an aggregate capacity of 40 Gb/s is transported over 40 km transmission distance with 32 splits. The TWDM-PON system at BER of 10−6 has shown a minimum receiver sensitivity of −22.78 dBm and −22.71 dBm for both downstream and upstream, respectively with maximum power penalty of 2 dB for downstream channel and 2.39 dB for upstream channel.

Performance Evaluation of DCF Length for High Scalability NG-PON2

Next Generation Passive Optical Network Stage 2 (NG-PON2) have to resolve the problem like demand each user, for example, HDTV, 3DTV, Hologram and Telemedicine. The research designed Passive Optical Network (PON), which is meet requirements of NG-PON2. Using stacked 4 Optical Line Terminal (OLT) with an aggregate 40 Gbps transmitted on fiber Single Mode Fiber (SMF) and Dispersion Compensation Fiber (DCF) by comparing the system without DCF cable. On the condition of minimum standards, the range of 40 km with a power splitter 1:64 only 9:01% power difference while the increased in the Q factor of 65.5%. With these results, it can be said that systems using DCF can be used optimally. In addition, with the power splitter 1: 4 and a lower power worth 0 dBm can produce a range of 150% further. With the same distance as far as 40 km, this research increasing power splitter 6 times increase compared with previous research.

Consideration of Tunable Components for Next-Generation Passive Optical Network Stage 2

Possible configurations of tunable components for the next-generation passive optical network stage 2 (NG-PON2) are reviewed on the basis of system requirements. Expected network functions in NG-PON2 systems along with the concept of in-service tuning in colorless ONUs are also reviewed.

A TWDM-PON with Advanced Modulation Techniques and a Multi-Pump Raman Amplifier for Cost-Effective Migration to Future UDWDM-PONs

Dense wavelength-division multiplexing passive optical networks and ultra-dense wavelength-division multiplexing passive optical networks are strong candidates to future next-generation passive optical network stage 3 access networks in order to satisfy increasing bandwidth demand, but their deployment is still a great challenge for telecommunication operators. Time and wavelength division multiplexed PON (TWDM-PON) has already been chosen by ITU-T as one of the best architectures in brownfield contexts to allow the reuse of the optical distribution network. Our proposal exploits the advantages of TWDM in order to reach a balance between coexistence with legacy systems and gradual and cost-effective migration towards pure wavelength division multiplexed PON (WDM-PON). In order to fulfill this aim, with reference to downstream traffic enhancement, two main novelties are presented: 1) the use of a multi-pump Raman amplifier (MRA) to satisfy the future necessity of large gain bandwidth; 2) the introduction of advanced modulation techniques to increase spectral efficiency and the future number of user channels (a less than 7 GHz-wide channel bandwidth providing 10 Gb/s bitrate has been demonstrated). A coherent system has been also proposed and its main impairments have been evaluated. The MRA has been accurately optimized to minimize power consumption without compromising performances. In the upstream direction, a semiconductor optical amplifier has been considered. The performances of the proposed TWDM-PON have been predicted through numerical simulations based on a system-level commercial CAD software.

Upgrade of an optical network unit in a 40 Gb/s time and wavelength-division multiplexed passive optical network using an upstream tunable colorless laser

A high data transmission rate is the main requirement for next-generation telecommunication networks. A design for a 40 Gb/s time and wavelength-division multiplexed passive optical network (TWDM-PON) for next-generation passive optical network stage 2 is presented. The use of a modulated grating Y-branch (MG-Y) laser is proposed as an upstream tunable colorless laser source to upgrade the optical network unit. The electronically tuned MG-Y externally modulated laser with a 10 Gb/s modulation rate is applied to a TWDM-PON and presented across a 3.2-nm tuning range. The performance of the proposed laser is analyzed in terms of bit error rate, eye diagram, and optical signal-to-noise ratio. The proposed TWDM-PON achieved an aggregated data rate of 40 Gb/s along 40 km of bidirectional fiber at a 1:128 splitting ratio without amplification and dispersion compensation.