Passive Optical Network System Research Articles

Multi-electrode quantum-dot semiconductor optical amplifier as an intensity modulator of signals in optical communication systems

In this paper, we are going to exhibit the system performance using the single, double and three-electrode quantum-dot semiconductor optical amplifier as an intensity modulator (3E-QD-SOA-IM) of the adaptively modulated optical orthogonal frequency division multiplexing (AMOOFDM) signals in the intensity-modulation direct-detection passive optical network (IMDD-PON) systems. Moreover, to compare the bit-rate versus transmission distance of the proposed fiber link model when using both configurations multi-electrode semiconductor optical amplifier intensity-modulator (ME-SOA-IM) and multi-electrode quantum-dot semiconductor optical amplifier intensity-modulator (ME-QD-SOA-IM), to study the improvement of the transmission capacity, distance reach and power efficiency when applying the proposed configurations for optical access networks for distances ranging from 20 km up to 120 km. The three-electrode configuration solved the nonlinearity of the two-electrode configuration and offered a considerably wider range of optimum operating conditions to achieve up to 35 Gbps. Furthermore, the 3E-QD-SOA-IM showed a better performance over the 3E-SOA-IM over all the 120 km, and a 5 Gbps enhancement in the bitrate with a 20 dB less optical input power at 20 km.

Low-complexity blind polarization demultiplexing and frequency domain equalization for coherent passive optical network systems

Algorithmic and architectural options and trade-offs between performance and complexity/power dissipation are necessary to consider in the transfer of coherent technology from long-haul transmission to short-reach application. An adaptive equalization algorithm cascading polarization demultiplexing and frequency domain equalization is proposed to target passive optical network applications that feature extremely low computational complexity. Three coordinate rotation digital computer-based vector rotators are introduced to realize polarization demultiplexing without performing multiplications. A simplified gradient descent algorithm is proposed to search and trace the state of polarization. A nonbutterfly adaptive equalizer in the frequency domain for each polarization is designed to handle link chromatic dispersion and the imperfection of the transceiver frequency response. The performance of the proposed equalization scheme is experimentally verified by a 32-GBaud dual-polarization Nyquist quadrature phase-shift keying system over 20-km standard single-mode fiber transmission. With the proposed method, the number of hardened multipliers for field-programmable gate array realization is reduced by ∼85 % compared with a conventional 2 × 2 multiple-input multiple-output finite impulse response filter with the same receiver sensitivity.

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.

A Comparative Study of Performances Between the WDM PON System and the CWDM PON System in an Optical Access Network

Abstract The growth of optical technology is currently being studied extensively to meet the significant demand for bandwidth. The passive optical network (PON) solves the problem of bandwidth as it extends the optical network to individuals and businesses [Sifta R, Munster P, Krajsa O, Filka M, “Simulation of bidirectional traffic in WDM-PON networks", Brno University of Technology, ISSN 0033–2097, R. 90 NR 1/2014.]. In this paper, a comparative study is made between the WDM PON system and the CWDM PON system using two different architectures, one for the WDM PON and the other for the CWDM PON, to illustrate the appropriate technique for the PON network by increasing the Q factor and the OSNR ratio while minimizing the bit error rate (BER < 10–9 ). Both systems are simulated at 10 Gbps for four users of bidirectional SMF (Single Mode Fiber) fiber lengths and different powers. In order to determine the transmission performance for both systems, the link was designed for fiber lengths of 20, 30, 40, 50 and 60 km as well as for powers from −10 dBm up to 10 dBm for four users. The use of the EDFA amplifier in the WDM PON system is required in this document to minimize degradation caused by attenuation [Parkirti RDK, Singh R. Cost-efficient Colorless WDM-PON Based on RSOA for High Capacity. Int J Adv Res Comput Eng Technol (IJARCET). 2016;5]. On the contrary, in the CWDM PON system, the amplification is not essential because the wavelengths used in this system are not affected by the water peak which causes a strong attenuation of the wavelengths in the 1370–1410 nm range on optical fibers [Nazir M, Arshad F, Asif R. Design and evaluation of power budget for a bidirectional CWDM-Passive Optical Network. In: International Conference on Communication, Computing and Digital Systems (C-CODE), Islamabad, Pakistan, 04 May 2017.]. The peak of water vapor absorption is close to 1383 nm.

Secure scheme for OFDM-PON system using TR based on modified Henon chaos

A modified Henon chaos mapping-based Tone Reservation (TR) method is presented to simultaneously improve the performance and security of orthogonal frequency division multiplexing passive optical network (OFDM-PON) system, which did not need any redundant sideband information. With the aid of high sensitivity of the low bits in the decimal part of chaos, the modified Henon chaos is constructed iteratively by extracting low bits of the previous chaotic value, which enhances the complexity and randomness of chaotic sequence values. And, by utilizing this chaos, the permutation vector can be conducted and is employed to scramble the distribution of reserved tones on the frequency domain and OFDM frames respectively, which can simultaneously achieve the peak-to-average power ratio (PAPR) reduction and data encryption. The feasibility of this scheme has been experimentally proven in 10-Gb/s OFDM-PON system through 20km fiber (SMF) transmission. Experimental results manifest that, compared to the common OFDM-PON system, the proposed scheme can achieve the ∼3dB PAPR reduction and ∼1dB BER improvement.

Next Generations of Optical Access Networks - NG-PON and NG-ЕPON

The work is devoted to an overview of the development of standards for telecommunication access networks based on new generation passive optical network (PON) technologies. PON systems are the # 1 cable broadband solution. International bodies are actively standardizing new options for PON technologies. PON technologies are standardized by two international organizations: ITU and IEEE. New standards of these organizations allow to significantly increase network bandwidth and expand the application area of PON technologies. Considered the latest ITU standardized technology, NG-PON2. The progress of work carried out by the IEEE on the standardization of new technologies, namely, 25G-EPON, 50G-EPON and Super-PON, is considered. The main difficulty in the implementation of new generation systems is noted.

Ecological environment fuzzy networking system protection based on optical fiber intelligent network

The optical fiber network has the characteristics of providing users with wider bandwidth and supporting the changing needs of more users. At the same time, the optical fiber network can also reduce the network infrastructure investment. The traditional Ad Hoc On-demand Distance Vector (AODV) algorithm does not consider the impact of node movement on the network, and the link disconnection frequently occurs during the routing process. The ant colony algorithm based on swarm intelligence only considers the unique factor of pheromone concentration to find the optimal path through multiple iterations, which will increase the complexity of the algorithm and affect the route establishment delay. In response to the above problems, this paper proposes a routing algorithm based on fuzzy logic. The algorithm can comprehensively consider the three factors of node location, mobility and signal strength, and greatly reduces the complexity of the algorithm. This paper gives a detailed definition of profust reliability of the Ethernet Passive Optical Network (EPON) system for distribution network communication and obtains the profust reliability parameters based on Monte Carlo simulation. After that, the reliability of profust under different networking modes was simulated, and the influence of network scale, component failure rate, component repair time and other parameters on the reliability of EPON networking profust was analyzed. The fuzzy probist reliability analysis method uses analytical methods, which are commonly used to deal with end-to-end reliability analysis problems and has certain limitations. Profust reliability analysis treats the system as a whole, which is more suitable for the reliability of complex end-to-multi-end systems.

PWC-PON: An Energy-Efficient Low-Latency DBA Scheme for Time Division Multiplexed Passive Optical Networks

Reducing network energy consumption and offering low-latency service quality have been the pursued goals in broadband passive optical networks (PONs). To realize these goals, energy-efficient dynamic bandwidth allocation (DBA) has been extensively studied. Nevertheless, few of these DBA schemes can effectively support low-latency and low-energy requirements, simultaneously. For these existing DBA schemes, the adopted energy-saving methods by sleeping some network elements would not handle the mismatch between the upstream and downstream bandwidth required by an optical network unit (ONU), which brings in a longer active window for each ONU and thus larger packet latencies. In this paper, an energy-efficient low-latency DBA scheme is proposed based on a novel pairwise combination (PWC) method. The essence of the PWC method is to compact the polling cycle length as much as possible by dynamically paring any two ONUs in complementary ways, which in turn also improves latency performance of data packets (i.e., quality of service (QoS)). Moreover, we introduce a multiple-state energy-saving mode into the proposed DBA scheme to reduce the PON energy consumption, with the consideration of both the upstream (US) and downstream (DS) transmissions. We establish an energy saving model for the proposed PWC-PON compared with the PONs with the existing DBA schemes, and also present a comprehensive M/G/1 queuing analysis with modification for the data latency performance. Extensive theoretical analysis and simulation results show that the proposed PWC-PON can reduce US and DS latency by 50% compared with the existing Gate Service (GS)-based DBA scheme. The energy saving efficiency is up to 3.5% higher than the benchmark when the US traffic load is light. It suggests that our PWC-based DBA scheme cannot only reduce the energy consumption, but also reduce the packet latency for PON system.

Zero Guard Band Multi-Twin-SSB System in Single Fiber Bidirectional PON Transmission

We propose a novel zero guard band (ZGB) multi-twin-SSB bidirectional passive optical network system which combines the multiband carrier-less amplitude phase and twin single sideband (SSB) modulation techniques. The multi-twin-SSB signal is generated at the downlink transmitter side with zero guard band between the left-sideband and right-sideband. A weak local oscillator which is extracted from the uplink optical source aids the downstream signal detection. Kramers-Kronig algorithm is used at both downlink and uplink receiver sides to reconstruct the SSB signal and eliminate the signal-signal beat interference. The downstream and upstream signals are transmitted in a single fiber without any spectral overlap between them and the Rayleigh backscattering noise is removed by the optical band-pass filter. The proposed scheme is extensively investigated and analyzed with four sub-bands using 50 Gbps 16-QAM modulation for each sub-band over a bidirectional 50 km transmission. The results show that, compared with the conventional multi-twin-SSB scheme, the proposed ZGB multi-twin-SSB scheme can improve the spectral efficiency by about 11%. The required optical signal to noise ratio (OSNR) and the required received optical power (ROP) can be reduced by more than 15 dB and 7 dB respectively at the 7% hard decision forward error correction (HD-FEC) threshold (bit error rate of $3.8\times 10^{-3}$ ), respectively. For the uplink transmission, the required ROPs for the inner and outer sub-bands at 7% HD-FEC are about −10 dBm and −11 dBm, respectively. And the signal to noise ratio to the corresponding ROPs for the inner and outer sub-bands are 15.4 dB and 15.3 dB, respectively.

Comparative investigation on 10G-class and 25G-class receivers for O-band DML-based 25/50 Gbps TDM-PON

Abstract Reliable and cost-efficient transceivers are desired for next generation high-speed passive optical network (PON). In this paper, we experimentally demonstrate 25/50 Gbps transmissions based on an O-band directly modulated laser (DML), and the receiver-side solutions are investigated in detail to realize a low-cost high-speed PON system. Specifically, a comprehensive comparison of two commercially available receiver candidates is presented, which are the 10G-class receiver and the 25G-class receiver. Three typical transmission cases for next generation PON systems based on these two receivers are demonstrated, and the system bandwidth limitation induced signal distortions in corresponding cases are compensated by equalization-based digital signal processing (DSP). System performances and the DSP-induced implementation complexity of the two receivers are comprehensively analyzed and compared. Results indicate that, for the 25 Gb/s transmission, the 25G-class receiver without any DSP is more favorable than the 10G-class one with post-equalization, and a power budget of 25.4 dB is achieved without amplification for non-return-to-zero on-off keying (NRZ-OOK) signal. While for the 50 Gb/s case, the two receivers manifest similar performances and DSP-induced hardware complexities, making both feasible solutions for real deployments, and after 20 km fiber transmission, an optimum power budget of 20.3 dB is achieved for the 4-level pulse amplitude modulation (PAM4) system.

Experiment Study of Downstream Traffic Balancing Strategy on 40G Long Reach Coherent PON

Abstract Distributed high-bandwidth consumption services such as cloud computing require large-capacity, long-distance, and wide-coverage development requirements for Next-Generation Passive Optical Networks (NG-PON2). With the development of NG-PON2 technology, the optical line terminal (OLT) device structure of passive optical network (PON) system is also increasingly complex and heterogeneous. This leads to the problem of network congestion and low bandwidth utilization caused by the unbalanced use of link and port resources in the traditional core network in the PON network. Based on the 40G coherent PON experimental system, this paper studies the traffic balancing problem of OLT equipment, and proposes a dynamic traffic balancing strategy based on real-time monitoring of load sharing and reporting of police and periodic adjustment. The experimental results show that the designed dynamic traffic balancing strategy can effectively reduce the PON network blocking rate and improve bandwidth utilization.

An efficient adaptive equalization architecture for high-speed coherent PON systems

Algorithmic and architectural options and tradeoffs between performance and complexity/power dissipation are imperative to be considered in the transfer of coherent technology from long-haul transmission to passive optical network (PON) application. In this work, a novel low-complexity equalization architecture cascaded two frequency domain equalizers (FDEQs) and one 1-tap 2 × 2 butterfly equalizer is proposed targeting PON applications. FDEQ is designed to handle link chromatic dispersion (CD) and the imperfection of transceiver frequency response. The 1-tap 2 × 2 butterfly equalizer is introduced to realize polarization demultiplexing. A simplified FDEQ tap coefficient calculation method is designed. The performance of the proposed equalization architecture is experimentally verified by a 32-GBaud dual-polarization (DP) Nyquist-QPSK system over 20-km standard single-mode fiber (SSMF) transmission. With the proposed method, the number of hardened multipliers for field-programmable gate array (FPGA) realization is reduced by ∼90% compared with conventional 2 × 2 butterfly equalizer, at the expense of 0.5 dB receiver sensitivity.

DSP-free single-wavelength 100 Gbps SDM-PON with increased splitting ratio using 10G-class DML.

We present beyond 100 Gbps space-division multiplexing passive optical network (SDM-PON) systems using commercial 10G-class directly modulated laser (DML) modulated with 25/28 Gbps data signals, with polarization-diversity micro-ring resonator (PD-MRR) to improve the extinction ratio (ER). A high-count multi-core fiber (HC-MCF) with low-crosstalk (XT) is used in the system, simultaneously increasing the transmission capacity and splitting ratio. Different cores of the HC-MCF are used for upstream (US) and downstream (DS) transmission, avoiding the Rayleigh backscattering noise. Thanks to compatibility with time-division multiplexing (TDM), the splitting ratio could be further increased. In addition, both symmetric and asymmetric SDM-PON architectures are proposed to meet different requirements of users. In the SDM-PON systems, a simple intensity modulation/ directly detection (IM/DD) is applied without digital signal processing (DSP), which may be a promising candidate for future large-capacity and high splitting ratio access networks.

The Outlook for PON Standardization: A Tutorial

In light of the 5G deployments, edge computing, and future high bandwidth services, the industry is rethinking the optical access network architecture design. Passive optical network (PON) with its efficient fiber infrastructure plays an essential role in this design transformation. This article reviews the driving forces shaping the new generations of PON systems in the coming years; and discusses the course of action in the FSAN Group, ITU-T, and IEEE standards bodies to address the impending requirements.

(Max-min model)-based mode-matched algorithm among subsystems in multisystem-based virtual passive optical network

With the development of passive optical network (PON), multiple PON systems using various multiplexing technologies can coexist. Virtualization technology is a preferable solution for multi-standard coexistence. In this paper, (max-min model)-based mode-matched algorithm is proposed in multisystem-based virtual passive optical network (VPON). By constructing a bipartite graph of the subsystems, a mode-matched graph is built. By introducing the concept of flow in mode-matched graph, max-min model is created. By the model, mode-matched algorithm is proposed. The maximum matching bandwidth and the minimum number of matching can be obtained by mode-matched algorithm. The utilization of network resources can be increased. Finally, the performance analyses and the simulations verify the effectiveness of the proposed algorithm.

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.

200 Gbit/s/λ PDM-PAM-4 PON system based on intensity modulation and coherent detection

A low-complexity and cost-efficient coherent detection-based 100 Gb/s or beyond passive optical network (PON) has attracted a lot of attention in recent years, as this technology offers high receiver sensitivity, colorless frequency selectivity, and linear detection enabling channel impairment compensation in the digital domain. We experimentally demonstrate the first single-wavelength 200 Gb/s coherent PON over 20 km downstream transmission with polarization division multiplexed four-level pulsed amplitude modulation (PDM-PAM-4) signals in the C-band. The intensity modulator replaces the costly in-phase/quadrature modulator, and hardware-efficient carrier recovery technologies are used for recovery of PAM-4 symbols. By using optimized Nyquist pulse shaping, the transceiver bandwidth can be reduced to within 50 GHz. A maximum power budget of 32.5 dB can be achieved for 200 Gb/s/λ PDM-PAM-4 at a bit error rate of 1 × 10 − 2 over 20 km fiber transmission. The possibility of a 200 Gb/s/λ PON is investigated using intensity modulation and coherent detection for the first time to our knowledge.

Optimization of QC-LDPC Codes by Edge Exchange Method Based on ACE

Long quasi-cyclic low-density parity check (QC-LDPC) codes have been chosen as one of the forward error correction (FEC) schemes in passive optical network (PON) systems benefiting from the excellent performance. About how to get the appropriate LDPC codes, some traditional methods which focus on obtaining large girth or flat approximated cycle extrinsic message degree (ACE) spectrums are proposed for the design of LDPC codes. These methods which may still make the existence of small stopping sets containing short cycles probably are not so useful for long QC-LDPC codes. Recently, the parallel vector message passing (PMP) algorithm oriented-to decreasing the number of short cycles is proved to be an effective method to optimize LDPC codes. Since ignoring short cycles with poor connectivity which can induce error floor, this method cannot guarantee its effectiveness for long QC-LDPC codes. In this letter, an edge exchange optimization method based on the global properties of ACE and girth called EEA method is proposed, which tries to reduce cycles with low ACE in the order of cycle length. The numerical results prove that our EEA method can bring the improvements of error floor up to two orders of magnitude to long QC-LDPC codes and obviously outperforms PMP algorithm.

Comparative Analysis of High Speed 20/20 Gbps OTDM-PON, WDM-PON and TWDM-PON for Long-Reach NG-PON2

Abstract Nowadays, bandwidth demand is enormously increasing, that causes the existing passive optical network (PON) to become the future optical access network. In this paper, next generation passive optical network 2 (NG-PON2) based, optical time division multiplexing passive optical network (OTDM-PON), wavelength division multiplexing passive optical network (WDM-PON) and time & wavelength division multiplexing passive optical network (TWDM-PON) systems with 20 Gbps (8 × 2.5 Gbps) downstream and 20 Gbps (8 × 2.5 Gbps) upstream capacity for eight optical network units has been proposed. The performance has been compared by varying the input power (−6 to 27 dBm) and transmission distance (10–130 km) in terms of Q-factor and optical received power in the presence of fiber noise and non-linearities. It has been observed that TWDM-PON outperforms OTDM-PON and WDM-PON for high input power and data rate (20/20 Gbps). Also, TWDM-PON shows its superiority for long-reach transmission up to 130 km, which is a cost-effective solution for future NG-PON2 applications.

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.