Wavelength Division Multiplexing Passive Optical Network Research Articles

Scheme for a WDM-PON with colorless optical network units based on a flat optical frequency comb.

A new, to the best of our knowledge, scheme for a wavelength division multiplexing passive optical network (WDM-PON) based on a flat optical frequency comb (OFC) is proposed. Using an OFC as the optical source of the system can realize the colorlessness of optical network units (ONUs), and the direct detection of the downlink data further simplifies the ONU structure. The coherent demodulation of the uplink data improves the system performance due to the coherence of the comb lines. In this research, the proposed system is studied for its performance and power budgeting. The results show the flexibility, effectiveness, and practicability of the proposed scheme, which can be applied to future high-capacity optical access networks.

تأثير ثلاث خطط مختلفة على المرحلة الثانية من الشبكات الضوئية في الجيل القادم

Abstract: In this work, a simulative analysis of 40 Gb/s downstream time and wavelength division multiplexing-passive optical network (TWDM-PON) for next-generation passive optical network second stage (NG-PON2) had been designed and demonstrated. The performance of three different wavelength plans in TWDM-PON are evaluated as the solution to NG-PON2 to support 40Gbit/s bandwidth requirement. A four 10-Gb/s TWDM-PON signals are stacked using four different wavelengths in the downstream direction and externally modulated. The system performance is observed using Bit Error Rate (BER) and Optical Signal-to-Noise Ratio (OSNR) with respect to the design parameters such as distance, number of users and received optical power. Thus, the proposed system was able to support 512 number of users and 80 km transmission distance. When the system is tested upon transmission of triple play services over 80km distance with 512 users, it is shown that BER of 8.9 × 10-10, 3.9 × 10-9 and 1.3 × 10-4 are achieved for data, voice and video, respectively.

Enhanced PON and AMCC Joint Transmission with GMM-Based Probability Shaping Techniques

In ITU-T standards, auxiliary management and control channels (AMCCs), as defined, facilitate the rapid deployment and efficient management of wavelength division multiplexing passive optical network (WDM-PON) systems. The super-imposition of an AMCC introduces additional interference to a PON signal, resulting in the degradation of the performance of the overall transmission. In prior research, we proposed employing a Gaussian mixture model (GMM) to fit a baseband-modulated AMCC signal. Following the analysis of the interference model and the distribution characteristics of received signal errors, we propose a combined optimization method for a transmitter and receiver in this paper. This method, grounded in probabilistic shaping (PS) techniques, optimizes the probability distribution of the transmitted signal based on the AMCC interference model, with the objective of reducing the error rate in PON signal transmission. We have validated this approach within a 50G-PON experimental system by utilizing PAM4 modulation. The experimental results demonstrate the effectiveness of this method for mitigating the impact of baseband-modulated AMCC, thereby reducing the error rate in PON signal transmission. The approach presented in this paper can further minimize the performance degradation introduced by baseband-modulated AMCC in WDM-PON systems, enhancing the efficiency of WDM-PON deployment.

Modelling and numerical analysis of combined dual impact of SRS and FWM on the performance of upstream and downstream channels of a novel UDWDM/DWDM-PON

Wavelength division multiplexing (WDM) is an important method in modern optical communication systems for both long-haul and access networks. Particularly, after being standardized by Telecommunication Standardization Sector of International Telecommunication Union (ITU-T), WDM passive optical network (WDM-PON) becomes a considerable choice for fronthaul implementations of 5G networks. Stimulated Raman scattering (SRS) and four-wave mixing (FWM) are crucial nonlinear impacts that significantly limit the performance of WDM-based optical fiber communication systems. In this paper, an ultra-dense/dense WDM-PON (UDWDM/DWDM-PON) architecture has been proposed and combined dual impact of SRS and FWM on performances of upstream channels (USCs) and downstream channels (DSCs) of the proposed UDWDM/DWDM-PON has been numerically analyzed. USCs have been assumed to operate in 1310 nm region while operating wavelength region of DSCs has been taken as 1550 nm. Simulations have been performed on both UDWDM-PON architectures with 3.125 GHz and 6.25 GHz channel spacings and DWDM-PON architectures with channel spacings between 12.5 GHz and 100 GHz. 2x15-channel and 2x63-channel system structures have been considered in simulations. Signal-to-crosstalk ratio (SXR) has been chosen as performance parameter and its variation with channel input powers, channel spacings and channel lengths have been simulated for both USCs and DSCs of 2x15- and 2x63-channel UDWDM/DWDM-PONs. Results show that the proposed UDWDM/DWDM-PONs using single G.652 fiber can exhibit a reliable communication with minimum 23 dB SXR performance under combined dual impact of SRS and FWM unless some highlights about input powers and channel lengths mentioned in the paper are neglected.

Evaluation of resource efficiencies for the non-symmetric dynamic wavelength allocation method applied in the P2MP WDM-PON network design

At present days, metropolitan and access communication networks are markedly developing utilizing a variety of technologies. Their bearer communication infrastructures will be mostly exploiting the optical transmission medium where wavelength division multiplexing techniques will play a key role. Wavelength-Division Multiplexed Passive Optical Networks (WDM-PON) attract considerable attention for the next generation optical metropolitan and access networked systems. Simultaneously, the utilization of common optical network resources in wavelength domains will be more important. The main purpose of this paper is presented by the evaluation of resource efficiencies for the non-symmetric dynamic wavelength allocation method applied in the WDM-PON network design with aconventional topology. This contribution introduces a novel non-symmetric Dynamic Wavelength Allocation (DWA) method for a selected network design with the utilization only passive optical splitters in remote nodes. This novel wavelength allocation method is oriented on minimizing anumber of working wavelengths that will be used for compliance of customers’ requests for data transmitting in the common point-to-multipoint WDM–PON network design. For evaluation of wavelength scheduling, a simulation model related to the conventional WDM-PON network design is realized in the MATLAB programming environment is presented with results. Finally, different traffic loading scenarios are determined and, subsequently, resource efficiencies of the presented non-symmetric DWA method are evaluated from aviewpoint of application in future WDM-PON network designs.

Fuzzy logic based dynamic wavelength and bandwidth allocation for 5G front haul networks

The Quality of Service (QoS) requirements for 5G are very strict in terms of latency of Fifth Generation (5G) traffic. 5G fronthaul networks between the baseband unit and remote radio heads are planned to use Next Generation - Passive Optical Networks 2 (NG-PON2) to carry their traffic. However, these Time Wavelength Division Multiplexing (TWDM) PON based networks also provide service to other traffic such as residential and corporate users. Therefore, it is crucial to provide QoS guarantees to 5G traffic. The main issue includes allocating transmission over multiple wavelengths while maintaining QoS. Although using all the available wavelengths all the time may seem to be the simple solution, each active wavelength increases the cost of operation. To solve these issues, this paper proposes a technique using fuzzy logic to dynamically allocate wavelength and bandwidth for 5G fronthaul networks. Two types of traffic, i.e., 5G traffic and normal traffic are considered while the problem of Dynamic Wavelength and Bandwidth Allocation (DWBA) is formulated as a queueing theory problem using penalties and a cost function. Penalties are assigned for waiting packets as well as each active wavelength. Then, modeling the number of active wavelengths, the number of packets in the system, the total cost, and the traffic intensity as input fuzzy variables while modeling the change in the number of active wavelengths as the fuzzy output variable. The Mamdani implication is used for the fuzzy inference engine and the height method is used for defuzzification of the output variable. Simulations in MATLAB show that the proposed technique can maintain the latency of 5G traffic lower than the defined threshold while also significantly reducing the number of active wavelengths. A comparison with the existing state-of-the-art techniques shows that the proposed technique results in an improvement of at least 46% and 29% in terms of the average number of active wavelengths and the average latency for 5G traffic, respectively.

Fronthaul latency and capacity constrained cost-effective and energy-efficient 5G C-RAN deployment

The third-generation partnership project (3GPP) has identified different new functional split points, defined as options 1–7, between the baseband unit (BBU) and the remote unit (RU) for the 5G centralized radio access networks (C-RANs). The functional splits facilitate lower fronthaul line rate and latency requirements while imposing technical complexity and cost-efficiency trade-offs. Among all the functional split options, the standardization groups such as 3GPP, Open RAN (O-RAN), and small cell forum have selected option-7 as the most suitable choice for the 5G C-RAN deployment that can meet the operator’s requirements. One of the biggest challenges for designing option-7 functional split-based C-RAN is the capacity and latency requirement fulfillment as specified by 3GPP, while minimizing the deployment cost. In this regard, we propose an optimization model for cost-effective and energy-efficient option-7 functional split-based C-RAN architecture using wavelength division multiplexed passive optical network (WDM-PON) in the fronthaul. For the given locations of the next-generation core (NGC) and the set of RUs, the proposed optimization model explores the most suitable locations for the placement of BBU pools and arrayed waveguide gratings (AWGs). It provides complete interconnection details among NGC, BBU pools, AWGs, and RUs. It also provides the optimal number of digital units in each selected BBU pool, the splitting ratio of each AWG, and maximum fronthaul reach, satisfying the fronthaul latency, capacity, and power budget constraints. To the best of our knowledge, for the first time, we estimate the worst-case queuing delay for the upstream traffic flow using the G/G/1 queuing model and investigate its impact on fronthaul latency and deployment cost for different RU configurations. We compare the performance of the proposed option-7 functional split-based C-RAN with the traditionally used option-8 functional split-based C-RAN in terms of the deployment cost and fronthaul latency improvement.

FPGA-Based Demonstration of WDM-PAM4-PON System With Low-Complexity CMA

We propose and experimentally demonstrate a low-complexity constant modulus algorithm (CMA) based on FPGA for 4-channel wavelength-division-multiplexing passive optical network (WDM-PON) employing 4-level pulse amplitude modulation (PAM4). The FPGA processes the 4 wavelength channels sequentially. In order to reduce the logic resources required by parallel equalization algorithm, an optimization based on parallel structure of constant mode algorithm (PCMA) was proposed in this paper. Different from the classic all-parallel structure CMA, our proposed PCMA adopts a new tap update structure, which only needs to update few sets of taps. With the help of the proposed structure, the resource of DSP is reduced to 21% on average. The PAM4 signal with a net rate of 110.24Gb/s transmission over 25-km SSMF can be achieved with the bit error rate (BER) less than 3.8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> .

A Dynamic Restructuring Algorithm Based on Flexible PON Slices

In recent years, with the introduction of the concept of the Internet of Things, a large number of terminals connected to the network, the pressure of network bandwidth is increasing. The bandwidth resources wasted by the traditional fixed access network architecture have attracted more and more attention of researchers. In order to meet the different needs of different users for service quality and improve the flexibility of network, network slicing technology arises at the right moment. Based on the slicing idea of the flexible time- and wavelength-division multiplexing passive optical network (TWDM-PON), a dynamic PON slice restructuring algorithm (DRA) is proposed in this paper. The proposed algorithm avoids the influence of previous slicing on subsequent slicing in the step-by-step slicing process, slices at the global level, and is less affected by the randomness of initialization. The simulation results show that the performance of DRA is about 10~30% higher than that of the dynamic optical network units (ONUs) grouping algorithm (DGA) and the dynamic ONU slicing algorithm (DONUSA) when there are 8 OLTs, and is about 30% higher than that of DGA and 10% higher than that of DONUSA when there are 16 OLTs. Therefore, the proposed DRA has more positive significance to relieve the traffic pressure in the increasingly tight bandwidth resources.

Enhancing performance and optimization of multichannel bidirectional WDM-PON with hybrid optical amplifiers employing diverse post dispersion compensation schemes

Abstract This paper is successfully demonstrated simulative comparison and investigation of 32 channels with 0.8 nm frequency spacing bidirectional wavelength division multiplexing passive optical network (WDM-PON) having 640 and 320 GB/s data rate in downstream and upstream transmission by using CRZ-DPSK/NRZ modulation formats respectively. The maximum reach of the system has been configured to 100 km by employing different post-dispersion compensation techniques such as EDC, DCF, OPC, and FBG in uplink and downlink transmission for compensate the effect of chromatic dispersion in propagating channel. An EDFA optical amplifier is placed after DCF for boosting the amplitude of weak signals downstream. Apart from this, the RSOA amplifier is installed at the ONT end for reflecting and re-modulates the same wavelengths to the CO terminal without using any external optical light source. The performance comparison of distinct compensation schemes are evaluated in terms of BER, Q factor, and Eye diagrams. It has been observed that the FBG and DCF are more robust compensation techniques as compared to EDC and OPC in the bidirectional WDM-PON. The maximum satisfying value of BER has been observed in downlink and uplink transmissions are 10−26 and 10−13 for FBG and DCF respectively.

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.

Next-generation WDM-PON optimized architecture for FTTH network with maximal resources for high throughput

Abstract To achieve high data rate, futuristic wavelength division multiplexing passive optical network (WDM-PON) has pursued due to capability of multiplexing individual wavelength. This paper illustrates the possibility of different data rates along with distance to solve the challenges for next-generation WDM-PON systems. It is superior to present PON design due to rapid progress in different passive components for access network. In this paper, recent progress such as 20 Gb/s (gigabits per second) to 80 Gbps. WDM-PON technology has been carried out. Due to recent development in PON systems, demonstration of 80 Gbps (10 Gbps per wavelength * 8) based WDM-PON system with simplified and optimized design for last mile is presented. The simulation results have been compared to demonstrate the effect of the results achieved. At last, better quality (Q)-factor of 3.46, low value of BER (bit error rate) i.e., 2.48 × 10−11 with reach of 80 km whereas high value of Q-factor of 22.16, eye height of 4.75 and BER of 3.61 × 10−10 has achieved successfully using WDM-PON system.

Hybrid Self-Protected Fiber-FSO WDM-PON System with Fiber Breakage Prevention

In this research, we present and design a blended wavelength-division-multiplexing passive optical network (WDM-PON) architecture to deliver both baseband and free-space optical (FSO) signals by using two wavelength bands over an available bandwidth to avoid the signal interference. Only using few additional components in the optical line termination (OLT) and optical network unit (ONU)/optical wireless unit (OWU) can achieve self-protected operation in the presented hybrid fiber-FSO access network against fiber breakage. In the measurement, eight WDM wavelengths with 24.3 Gbit/s on-off keying (OOK) modulation format are applied to verify and discuss the bit error rate (BER) performances of baseband and FSO signals, respectively, through 25 km fiber and 2 m wireless FSO connections. Therefore, the presented PON not only can deliver both baseband and FSO traffics, but can also provide a self-restored mechanism against fiber fault.

AMCC nonlinear baseband superimposition and extraction aided by proposed interference cancellation for WDM-PON used in 5G mobile fronthaul.

As the demand for mobile Internet capacity explodes, the research on fifth-generation (5G) mobile communication systems has gradually deepened, which has stringent requirements for latency and transmission capacity, especially in the section called mobile fronthaul (MFH). Wavelength division multiplexing passive optical network (WDM-PON) is an attractive technology for 5G MFH which requires an auxiliary management and control channel (AMCC) to achieve efficient network deployment. In previous studies, more research has been done on AMCC superimposition methods and transmission performance on 10 Gbps WDN-PON systems, and the role of AMCC in wavelength management has been studied at the system level. In this paper, we realize non-linear baseband modulation of AMCC signals up to 20 Mbps in a single wavelength 25-Gbps PON system through the distributed feed-back laser and Mach-Zehnder modulator. At the receiving end, we propose a low-complexity interference cancellation method to suppress the interference caused by WDM-PON signals and significantly reduce the bit error rate of AMCC signals. The method realizes a simplified scheme to reconstruct the PON signals by analyzing the characteristics of nonlinear modulation and the reconstructed signals can be applied to the original AMCC signals through filtering and subtraction to eliminate interference. These operations have low complexity and can be easily implemented by analog circuits, thus making it an effective way to improve the quality of AMCC signals. With the help of the proposed method, AMCC transmission at 20 Mbps can be achieved with different modulation depths, which is very promising for 5G MFH.

Single-step etched two-dimensional polarization splitting dual-band grating coupler for wavelength (de)multiplexing.

Diffractive periodic-structure-based grating couplers (GCs) are the most widely used devices for light coupling between optical fibers and integrated photonic devices. However, conventional GCs have limited wavelength operation and are polarization specific, which is due to the intrinsic radiation angle dependency on both wavelength and polarization. Here we propose and experimentally demonstrate a polarization-splitting dual-band grating coupler (PS-DBGC) for polarization diversity and wavelength division (de)multiplexing (WDM) operation. The four-port two-dimensional PS-DBGC is based on a periodically arranged structure with square holes, and requires only a single etch step in a 340-nm silicon-on-insulator platform. The simulation predicts that the maximum coupling efficiency (CE) of the proposed PS-DBGC is -2.8 dB and -4.6 dB for the O- and C-band, respectively. The measured peak CEs of the fabricated device are -4.7 dB at 1280 nm and -8.4 dB at 1522 nm. We anticipate that this PS-DBGC could potentially improve the performance of any future integrated WDM passive optical network.

Research of fiber nonlinear effects in WDM-PON based 5G fronthaul networks

In fifth-generation (5G) fronthaul networks, the wavelength division multiplexing passive optical network (WDM-PON) is considered as an important tool to address the advanced transmission requirements. The nonlinear effects occur when multiple wavelengths are transmitted simultaneously in the same optical fiber. In this paper, we investigate the four-wave mixing (FWM) and the cross-phase modulation (XPM) effects by using non-return-to-zero (NRZ), 4-level pulse amplitude modulation (PAM4), and optical duobinary (ODB) modulation formats in WDM-PON-based 5G fronthaul networks. The results show that ODB performs better when it comes to limiting the FWM and XPM effects because of its precoded attribute. Compared to the unpredictable sensitivity penalty based on NRZ and PAM4, the FWM-induced sensitivity penalty using ODB is reduced to 2[Formula: see text]dB. Moreover, the XPM-induced sensitivity penalty is measured as 1[Formula: see text]dB by adopting ODB, which is almost 5[Formula: see text]dB better than NRZ and PAM4 modulation formats.

Integrated Fiber-FSO WDM Access System with Fiber Fault Protection

In this study, we propose a new wavelength-division-multiplexing passive optical network (WDM-PON) system to support the blended fiber-free space optics (FSO) signal access. To provide the fiber and FSO traffics simultaneously, the C- and L-band channels are applied in the presented PON, respectively. Moreover, to avoid the fiber breakpoint in the fiber access traffic, the proposed WDM access architecture also can provide the self-restored mechanism by applying simple fiber routing path. In addition, the corresponding signal performances of fiber and FSO channels are also executed experimentally for demonstration.

SOA Assisted Wavelength Reusing for 25G Colorless PON With Low-Cost 10G EAM

This paper demonstrates a C-band 25G colorless passive optical network (PON) based on semiconductor optical amplifier (SOA) and 10G electro-absorption modulator (EAM). The experimental results show that the SOA in the optical network unit (ONU) can erase the downlink signal by taking advantage of the gain saturation feature, realizing the reuse of downstream wavelength. Meanwhile, the SOA gain can compensate for the EAM loss by optimizing the current and injection power. Apart from this, equalization algorithms at the optical line terminal are investigated for linear and nonlinear impairments compensation. Besides, the system robustness to the ASE and the maximum transmission speed are also evaluated. Finally, the system capacity can reach up to 25 Gbps with NRZ format at a bit-error ratio threshold of 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> , proving that this system is a promising technology for future high-speed colorless 2 × 25G or 4 × 25G Wavelength division Multiplexing (WDM) PON system.

Channel Characteristics Based Adjustable Fingerprint for Identity Authentication in WDM-PON With Deep Neural Networks

Wavelength-division-multiplexed passive optical network (WDM-PON) has been widely deployed for the high-speed, reliable transmission and low-cost properties. The physical layer identity authentication in WDM-PON becomes increasingly prominent. Recently, many device fingerprint based identity authentication schemes are proposed. However, these schemes only realize constant fingerprint, which will be acquired by illegal ONU after optical spectrum analysis. Therefore, the higher-level security requirement cannot be satisfied. To solve the problem, we propose a physical layer identity authentication method in WDM-PON by exploiting the channel characteristics based adjustable fingerprint with deep neural networks (DNNs). By secretly negotiating with legal optical network units (ONUs) on the lengths of the local fibers applied by them, the optical line terminal (OLT) can acquire the unique channel characteristics fingerprint obtained by each legal ONU. It should be noted that the fingerprint can be adjusted by modifying the length of the local fiber. Moreover, the same number of DNNs as legal ONUs are trained for fingerprint identification. Simulation results show 100% identification accuracy for illegal ONU when the length deviation between two fibers applied by legal ONU and illegal ONU is greater than 1.5 km. Meanwhile, the identity of each legal ONU can be recognized with 100% accuracy.

WDM-PON for 5G Wireless Fronthaul

While the idea of wavelength-division multiplex passive optical network (WDM-PON) has been around for many years, it has never been taken up in a significant way, mostly due to a lack of demand for its level of bandwidth. Fifth generation (5G) wireless has brought with it new centralized architectures that seem to require very-high-performance fixed networks. This article considers the use of WDM-PON for 5G wireless, the key finding is that its suitability depends on the deployment scenario for the service area in question. There are places that could benefit from such a system. The results of an initial trial of this technology are provided, proving system feasibility. A new type of hybrid PON system architecture combining WDM-PON and 50 Gb/s time-division multiplex PON (TDM-PON) networking is discussed.