Generation Optical Networks Research Articles

What is beyond 50G: future standards of optical access networks [Invited

In the past two decades, optical access networks have been widely deployed by operators around the world. The global optical access network market reaches about 1 billion users with a revenue of over 10 billion US dollars. As strategic tools to facilitate mass production, the optical access network standards play a crucial role in driving the product deployment and market growth. This paper overviews the latest effort in international standards bodies on the next generation optical access networks. It discusses projects in this area within the International Telecommunication Union’s Telecommunication Standardization Section (ITU-T), the IEEE, and the European Telecommunications Standards Institute (ETSI). Promising technologies are investigated with the goal of providing rates beyond 50 Gbps. Challenges are highlighted to satisfy the requirements on balancing access rates, loss budgets, and cost. Candidate systems are analyzed in three categories: point-to-multipoint (PtMP), point-to-point (PtP), and new applications. These standardization endeavors will jointly guarantee optical access networks as the premiere solution of wireline broadband access.

Energy efficient optimization using RTSO machine learning approach towards next generation optical network circuit for smart cities

Energy efficient optimization using RTSO machine learning approach towards next generation optical network circuit for smart cities

Pumping scheme for Holmium‐doped fiber amplifiers using traditional 1480 nm pumps exploiting cascaded lasers implemented using fiber Bragg gratings

AbstractDiversity in design is an important factor that enables developers to explore techniques aiming to reduce cost, complexity, and manufacturability. The optical window around 2000 nm is attracting rapid research considerations for the next generation optical networks as a continuation of C‐, L‐, and U‐bands. Optical amplifier is considered to be one of the major research directions in this optical window. Holmium‐doped fiber amplifier is an appropriate component to amplify signals in this optical window. But, the major issue is the pump laser for pumping the Holmium‐doped fiber (HDF) is that it is costly and not readily procurable. In a pioneering design, the authors introduced a method to pump the HDF using traditional 1480 nm pump diode by taking the advantage of cascaded lasers which were made of Erbium‐doped fiber (EDF) and Thulium‐doped fiber (TDF). In this paper, we propose an alternate method for pumping the HDF using commercially available 1480 nm pump diode by exploiting cascaded lasers implemented using two pairs of reflective fiber Bragg gratings (FBGs) and pieces of EDF and TDF. The EDF in the first laser is excited with a standard 1480 nm pump diode to create 1610 nm continuous wave (CW) laser which is used to excite the TDF in the second laser to generate 1950 nm CW laser that is used to pump the HDF. Peak gain of 40.5, 36, and 23 dB can be attained corresponding to –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Output powers of 10.5, 21, and 23 dBm are obtained for –30, –15, and 0 dBm signal powers, respectively at 2055.6 nm signal wavelength. Noise figures (NFs) of 5, 4.2, and 4 dB are observed at signal wavelength of 2066.7 nm for signal powers of −30, −15, and 0 dBm, respectively. Penalty of 4.5 dB has been observed both in peak gain and power at 2055.6 nm signal wavelength for signal power of −15 dBm considering the pair induced quenching. Finally, the proposed alternate pumping scheme is compared with the previous pumping scheme in terms of 3 dB gain bandwidth and NF. It has been observed that 88% increase in 3 dB gain bandwidth and 19% decrease in NF at a signal wavelength of 2044.4 nm for signal power of –30 dBm is noticed in the proposed pumping scheme.

Performance enhancement of passive optical network with improved bandwidth utilisation and allocation

Abstract In the past decade optical network is growing very rapidly due to the low noise, less bit error rate as well as bandwidth utilization of the network. In this paper explored the bandwidth utilization with the improved gain with less noise and low bit error rate. Previously worked had been done on this area up to the 2nd stage of the optical networks. Previous worked explain the utilization of the bandwidth also explore the allocation of bandwidth in between the two different networks. They also find out the different optimized parameters like bit error rate, delay, gain, and low noise using different methods. But this paper explored up to the fifth stage of the optical network with the optimum parameters has been found out after the simulation. It also explains the bandwidth reuse to the next level of the optical network without any delay provided in between the two consecutive stages. In this explored the future prospective of the next generation optical network and also explain the different module of the stages.

Bistable All‐Optical Devices Based on Nonlinear Epsilon‐Near‐Zero (ENZ) Materials

AbstractNonlinear and bistable optical systems are a key enabling technology for the next generation optical networks and photonic neural systems with many potential applications in optical logic and information processing. Here, a novel bistable resonator‐free all‐optical waveguide device based on indium tin oxide as nonlinear epsilon‐near‐zero material providing a cost‐efficient and high‐performance binarity photonic platform is proposed. The salient features of the proposed device are compatibility with silicon photonics, enabling sub‐picosecond operation speeds with moderate switching power. The device can act as an optical analogue of memristor or thyristor and can become an enabling element of photonic neural networks not requiring OEO conversions.

Flexible and adaptive coherent PON for next-generation optical access network [Invited

With the official adoption of the single-wavelength 50G PON standard at the International Telecommunication Union Study Group 15 (ITU-T SG15) meeting, both industry and academia have started extensive research on the next-generation optical access network beyond 50G. It is envisioned that 100G and 200G per wavelength and even beyond will be required in the next-generation optical access network to support the continuously growing bandwidth demands. Coherent passive optical network (C-PON), which is based on multi-access coherent optics and digital signal processing (DSP), appears to be a promising candidate for future 100/200G and even beyond single-wavelength PON, thanks to its superior sensitivity compared with current direct-detection based PONs. Actually, multi-access coherent optics brings many benefits to the optical access network beyond the improvement of sensitivity. In this invited paper, we review recent studies and progress on the flexible C-PON for optical access network in terms of access speed, multiple-access architecture, and deployment scenarios. Rate-adaptive coherent access is first introduced in this paper as a promising solution to achieve flexible C-PON. Adaptive modulation formats based on constellation shaping is highlighted to realize fine granularity of information rate and wide flexibility. We have also discussed the flexible multiplexing schemes beyond TDM, to take the full advantages of coherent access. Finally, we analyze the flexible deployment scenarios under the large power budgets thanks to coherent detection. All these flexibilities provided by coherent access would be interesting and beneficial in the next generation optical access network.

A DYNAMIC BANDWIDTH ALLOCATION SYSTEM IN XG-PONS BASED ON STATISTICAL ESTIMATION OF BUFFER INPUTS AND OUTPUTS

The exchanges in the New Generation Optical Access Network (NG-PON), are mainly based on the bandwidth request by the Optical Network Units (ONU) and its granting by the Optical Line Termination (OLT). This process (request-grant) not being synchronized, will create in the ONU buffer a long delay and the loss of sensitive packets. Many authors, from signaling to prediction, have proposed models to control these parameters, however only those based on prediction reduce the delay in the queues but also waste bandwidth by over- or under-allocating. Our goal is to propose a model that accurately allocates bandwidth to ONU while minimizing their queue delay. As such, we propose a Statistical Queue Estimation model based on ONU Buffer Inputs and Outputs (ESTEST). In its execution ESTEST memorizes the ONU bandwidth requirements and the bandwidth used to transmit their data in the ith upstream frames. With these two parameters (requirements and bandwidth used), our algorithm computes the traffic intensity (𝜌) and predicts the queue size of the ONU. On 100 observations we compute the mean and standard deviation of the 𝜌th values and with the reduced centered normal distribution, find the confidence interval of size estimation.

Suppression of Four Wave Mixing Effects Under Different Spectrally Efficient Modulation Techniques in Hybrid DWDM-OTDM Systems

Next generation optical networks require high spectral efficiency to meet the demand of high bandwidth for ultra-long haul communication. Spectrally efficient modulations using hybrid DWDM-OTDM systems can be used to achieve this. However, fiber nonlinearities such as four-wave mixing (FWM) will increase simultaneously and this will degrade the performance of WDM optical system. This paper explores the FWM reduction in 32 channels, 40 Gb/s hybrid DWDM-OTDM network using RZ-OOK, 16-QAM and PDM-QPSK modulation format at 200 GHz and 100 GHz channel spacing. Optical received power, BER, Q- factor, eye diagram and FWM side band power are analyzed at -15dBm to +15dBm channel power. All these modulations have shown a significant reduction in FWM. In addition, the 16-QAM gives highest reduction in FWM along with least BER of 7.9×10−158 and maximum Q-value of 27.74.

A Machine Learning-Based Framework for Predictive Maintenance of Semiconductor Laser for Optical Communication

Semiconductor lasers, one of the key components for optical communication systems, have been rapidly evolving to meet the requirements of next generation optical networks with respect to high speed, low power consumption, small form factor etc. However, these demands have brought severe challenges to the semiconductor laser reliability. Therefore, a great deal of attention has been devoted to improving it and thereby ensuring reliable transmission. In this paper, a predictive maintenance framework using machine learning techniques is proposed for real-time heath monitoring and prognosis of semiconductor laser and thus enhancing its reliability. The proposed approach is composed of three stages: i) real-time performance degradation prediction, ii) degradation detection, and iii) remaining useful life (RUL) prediction. First of all, an attention based gated recurrent unit (GRU) model is adopted for real-time prediction of performance degradation. Then, a convolutional autoencoder is used to detect the degradation or abnormal behavior of a laser, given the predicted degradation performance values. Once an abnormal state is detected, a RUL prediction model based on attention-based deep learning is utilized. Afterwards, the estimated RUL is input for decision making and maintenance planning. The proposed framework is validated using experimental data derived from accelerated aging tests conducted for semiconductor tunable lasers. The proposed approach achieves a very good degradation performance prediction capability with a small root mean square error (RMSE) of 0.01, a good anomaly detection accuracy of 94.24% and a better RUL estimation capability compared to the existing ML-based laser RUL prediction models.

Investigation of WDM-MDM PON employing different modulation formats

Advancement in the technology and optical communication sector has led to an increase in the demands of high bit rate and bandwidth, required for reliable data transmission. To meet such demands, future generation optical networks came into existence. In this paper, we propose a 100 Gbps, 4-channel WDM-MDM PON with two input wavelengths of 1550 nm and 1555 nm and using LP 01 and LP 11 modes. The system performance has been analyzed for different internal parameters considering return-to-zero (RZ), non-return-to-zero (NRZ), alternate mark inversion (AMI) and duobinary return-to-zero (DRZ) modulation schemes. DRZ modulation outperforms the other encoding schemes resulting in achievement of an acceptable bit error rate (BER) of ≤ 10−14 over 10 km of fiber length at a 25 Gbps data rate.

A novel expandable intersection‐ring architecture supporting optical network units' discretionary peer‐to‐peer communication in metro‐access network

SummaryDirect communication between optical network units (ONUs) provides the opportunity to reduce substantial latency among two communicating ONUs, which is very significant for next generation optical networks. In this paper, an expandable intersection‐ring architecture to support direct communication among ONUs is proposed. By adopting two tunable fiber Bragg gratings (FBGs), direct peer‐to‐peer communication of ONUs can be achieved. By utilizing the cyclic routing property of arrayed waveguide grating (AWG), upstream/downstream communication together with direct communication among ONUs can be carried out simultaneously. By adopting intersection‐ring topology, any two adjacent flexible expansion nodes (FENs) on the main ring can be used as intersections to extend a new subring, the scale of the network can be enhanced greatly. Meanwhile, not only the protection of multiple fiber faults can be realized, but also the fault protection of key nodes can be performed. By using a strategy of transmitting signals separately from the top and the bottom branches of the ring, communication efficiency can be improved, transmission latency can be reduced, and fault isolation can be achieved effectively. By the simulation experiment, the effectiveness of the proposed network is demonstrated.

A deep neural network with a fuzzy multi-objective optimization model for fault analysis in an elastic optical network

The elastic optical network (EON) is the most attractive architecture for the next generation of optical networks. Dealing with high bit-rate traffic, EON faces the challenge of ensuring survivability to operate with stringent Service Level Agreements. This article proposes a Deep Neural Network model with a multi-objective Fuzzy Inference System (FIS) to solve the Routing and Spectrum Assignment problem with Shared Backup Path Protection. The algorithm aims to optimize the trade-off between blocking probability (BP) and fault restoration ratio (FRR). It uses a new spectrum-fragmentation metric to improve the FRR of affected connections. The FIS adds features of load balancing and alignment of allocation path solutions. We use figures of merit as BP of connection requests, FRR, spectrum utilization ratio, and connection downtime to evaluate the algorithm performance. The proposed algorithm organizes traffic in a less fragmented way, efficiently uses routing and protection resources, and performs well compared to similar algorithms related in the literature.

Performance Analysis of DPSK Technique for Optical Transmission Systems

The long-distance high data rate transmission is accompanied by many transmission defects, which reduce the performance of optical communication systems. Therefore, due to the need to increase data capacity for the end user, signal regeneration techniques were used to mitigate these non-linear defects in the electric or optical field. Several techniques used to modify the optical signal, which is the possible solution to reduce the limit of non-linear transmission defects, especially before converting the signal from the optical field to the electric field. Since most of the techniques used to reduce the attenuation in the optical signal do not have the ability to reduce the error rate to reach a bit error rate (BER) less than 10-10 with a transmission capacity less than -10dBm. In this paper, the performance evaluation of DPSK has been validated for its adequate use in transmission systems. Nevertheless, the performance of the DPSK optical system was assessed to rely on a different coding format such as: Return to Zero (RZ) & Non-Return to Zero (NRZ-DPSK). The system is designed to withstand high data rate on long-distance optical transmission systems. The system investigated was simulated with OptiSystemTM 13.0 commercial software. The investigated system demonstrated the ability to mitigate nonlinear impairments from the noisy optical DPSK system with high bit-error rate (BER) improvement at low power transmission. Optical DPSK demonstrates the ability to send high-rate data transmission systems for use in the next generation of optical networks.

High-Speed Plasmonic Electro-Optic Beam Deflectors.

Highly integrated active nanophotonics addressing both device footprint and operation speed demands is a key enabling technology for the next generation optical networks. Plasmonic systems have proven to be a serious contender to alleviate current performance limitations in electro-optic devices. Here, we demonstrate a plasmonic optical phased array (OPA) consisting of two 10 μm long plasmonic phase shifters, utilized to control the far-field radiation pattern of two subwavelength-separated emitters for aliasing-free beam steering with an angular range of ±5° and flat frequency response up to 18 GHz (with the potential bandwidth of 1.2 THz). Extreme optical and electrostatic field confinement with great spatial overlap results in high phase modulation efficiency (VπL = 0.24 Vcm). The demonstrated approach of using plasmonic lithium niobate technology for optical beam manipulation offers inertia-free, robust, ultracompact, and high-speed beam steering.

Highly Reliable Metro-Access Network Based on a Dual-Fiber Ring Architecture and Optimized Protection Mechanisms

Network reliability is very important for the next generation of optical networks. In this paper, a highly reliable protection mechanism, which integrates the approaches of optical protection and microwave protection, is proposed for metro-access optical networks based on the wavelength division multiplexing (WDM) technique. By designing a scheme for the convergence of optical and wireless access and cooperating with designed remote nodes (RNs), not only can access for both wired and wireless service be provided simultaneously in each optical network unit (ONU) but also microwave protection can be realized when a failure occurs in a distribution segment. By developing a novel optical switch module (OSM) to cooperate with the dual-fiber ring structure, flexible switching can be achieved to protect against multiple types of failures in the feeder segment, including single-fiber faults, dual-fiber faults and multifiber faults. Based on the above structure, the influence of Rayleigh backscattering (RB) noise can be mitigated when the network is operating under all operating scenarios except for an inner-fiber fault. To further mitigate the influence of noise, optimization for upstream transmission performance is implemented by configuring a reflective semiconductor optical amplifier (RSOA). Furthermore, the feasibility of the overall scheme is verified through experiments and simulations under different operating conditions. The results show that the proposed mechanisms can achieve acceptable bit error rate performance and quality of service (QoS) metrics while also offering various advantages, including high reliability, large scale, and a relatively low cost.

Adaptive Transceiver Architecture With QoS Provision for OCDMA Network Based on Logic Gates

Utilization of an adaptable transceiver with quality of service (QoS) features is a promising notion to build next generation optical network. This paper proposes an adaptive transceiver design by adopting logic gates in the optical domain. The proposed design offers multiple scenarios to support QoS diversity with a slight modification of conventional optical code division multiple access (OCDMA) transceiver architecture through Sigma Shift Matrix (SSM) signature code. In particular, the proposed transceiver design categorizes the users into two classes of service, one having a higher quality level and the other having a lower quality level. Users of high class transmit at low interference versus high interference power for low classes’ users. To switch between the multiple scenarios, an optical Mux performs digital operation is developed and integrated to the transceiver design. This type of MUX is built by using a semiconductor optical amplifier (SOA). In addition, a comprehensive algorithm is developed to control the function of the adaptable transceiver. Five scenarios were formed and investigated to offer a platform for a different type of applications. A proof concept using Optisystem software demonstrates ability of the proposed architecture to efficiently switch between different levels of QoS as per user requirement and provide desired transmission capacity

Optical service unit (OSU)-based next generation optical transport network (NG OTN) technology and verification

With the development of transmission technologies, optical transport network (OTN) has evolved from a digital encapsulation technology to a network technology that supports multi-service transport. As the OTN gradually expands to the edge of the metropolitan area network (MAN) and enterprise users have higher quality requirements on bandwidth and service security, more and more private line services are provided via OTN network. Therefore, the OTN container is transformed from an optical data unit (ODU) to an optical service unit (OSU). The OTN industry has studied several OSU technologies to fit the development trends of NG OTN, aiming at transporting 2 Mbit/s to 100 Gbit/s constant bit rate (CBR) services and Ethernet services with high efficiency and more flexibilities, as well as reducing OTN network deployment and operation and maintenance (O&M) costs. In this work, several key technologies in NG OTN are introduced including NG OTN technical architecture, OSU frame format, client mapping and OSU multiplexing. Based on these technologies, we (China Mobile) took the lead in conducting the industry's first NG OTN test in Qingdao, which verified the service transport capability and lower latency performance of OSUs and promoted the maturity of the NG OTN industry chain.

Joint Minimization of Spectrum and Power in Impairment-Aware Elastic Optical Networks

Flexible-grid elastic optical networks (EONs) are widely considered as the future of next generation optical transport networks. Depleting spectral resources and increasing power consumption are two critical bottlenecks of EONs. In this paper, we propose a novel impairment-aware resource allocation scheme that jointly minimizes bandwidth waste and power consumption of EONs. The proposed scheme is presented in the form of an analytical optimization for small-sized networks. A low-complexity heuristic is then proposed for large networks. Numerical results show that by appropriately assigning the route, modulation format, and carrier frequency to each connection request, the proposed scheme significantly increases spectral efficiency and reduces power consumption in networks that handle varying traffic volumes.

A Comparative Evaluation of Nature Inspired Algorithms for Telecommunication Network Design

The subject of the study was an application of nature-inspired metaheuristic algorithms to node configuration optimization in optical networks. The main objective of the optimization was to minimize capital expenditure, which includes the costs of optical node resources, such as transponders and amplifiers used in a new generation of optical networks. For this purpose a model that takes into account the physical phenomena in the optical network is proposed. Selected nature-inspired metaheuristic algorithms were implemented and compared with a reference, deterministic algorithm, based on linear integer programming. For the cases studied the obtained results show that there is a large advantage in using metaheuristic algorithms. In particular, the evolutionary algorithm, the bees algorithm and the harmony search algorithm showed superior performance for the considered data-sets corresponding to large optical networks; the integer programming-based algorithm failed to find an acceptable sub-optimal solution within the assumed maximum computational time. All optimization methods were compared for selected instances of realistic teletransmission networks of different dimensions subject to traffic demand sets extracted from real traffic data.

An overview of ML-based applications for next generation optical networks

Over the past few decades, the demand for the capacity and reliability of optical networks has continued to grow. In the meantime, optical networks with larger knowledge scales have become sources of numerous heterogeneous data. In order to handle these new challenges, many issues need to be resolved, among which the low-margin optical networks design, power optimization, routing and wavelength assignment (RWA), failure management are quite important. However, the use of traditional algorithms in the above four applications shows some shortcomings. Fortunately, artificial intelligence (AI), especially machine learning (ML), is regarded as one of the most promising methods to overcome these shortcomings. In this study, we review the applications of ML methods in solving these four issues. Although many ML-based researches have emerged, the applications of ML techniques in optical networks still face challenges. Therefore, we also discuss some possible future directions of investigating ML-based approaches in optical networks.