Wavelength Division Multiplexing Optical Networks Research Articles

Cost minimization of multi-class demands groomed over multi-rate OTN interfaces considering WDM-layer constraints

This paper introduces a practical comprehensive approach to optimize the cost of installed Optical Transport Network (OTN) interfaces, as well as the required number of wavelengths in the substrate Wavelength Division Multiplexing (WDM) optical network. The approach assumes grooming variable-bit-rate traffic demands on multi-rate OTN interfaces. We propose an Integer Linear Programming (ILP) formulation to address the combined problem of OTN interface deployment, virtual-network formation, traffic grooming on the established distinct-capacity virtual paths, and virtual network embedding on the WDM physical substrate. The presented model focuses on mitigating the capital expenditure required to deploy OTN interfaces, usually the most costly element in the network, as well as minimizing the required number of wavelengths in the Routing and Wavelength Assignment (RWA) problem, contributing to the overall reduction in network costs and ensuring open capacity for future expansions. As the RWA problem is NP-hard and involves significant computational costs, we also propose a multi-step heuristic approach to tackle larger network instances more efficiently. In this approach, the optimization steps for the OTN design and the RWA solutions are conducted independently. For the OTN-layer planning, the optimum ILP formulation (OTN-ILP) is maintained, so that the optimum solution for the cost of installed interfaces on the OTN layer is guaranteed. The RWA problem is proposed through either an ILP formulation (RWA-ILP) or a heuristic approach. The RWA-ILP model can find the same or slightly superior number of wavelengths compared to the optimum solution of the Integrated ILP formulation, but it can provide results in reasonable times only for small networks. On the other hand, the heuristic RWA is able to run any network size, but it requires more wavelengths compared to the RWA-ILP model.

Architecture for low-cost and highly flexible metro-access networks using SOA-based OADM nodes and digital subcarrier multiplexing with power loading.

Metro-access networks exploiting wavelength division multiplexing (WDM) to cope with the ever-growing bandwidth demands are sensitive to cost and need to be fast-configurable to meet the requirements of many new network services. Optical add-drop multiplexers (OADMs) are a key component in enabling fast dynamic wavelength allocation and optimization. In this Letter, we propose and demonstrate, to our knowledge, a novel architecture for high-performance metro-access networks that utilizes semiconductor optical amplifier (SOA)-based OADM nodes, digital subcarrier multiplexing (DSCM), low-cost direct detection receivers, and power loading techniques, which makes the designed metro-access network cost-effective, fast reconfigurable, and flexible for bandwidth allocation on demand. Through a proof-of-concept experiment, we have successfully demonstrated a prototype horseshoe optical network consisting of up to four SOA-based OADM nodes at 40 Gb/s per wavelength channel by leveraging the proposed scheme. The flexible bandwidth allocation and dynamic add and drop operations have also been achieved in an emulated WDM optical network. All results indicate the great scalability and flexibility of the proposed architecture.

Performance analysis of hybrid optical amplifiers for multichannel wavelength division multiplexed (WDM) optical networks

Abstract Hybrid Optical Amplifier (HOA) has made a significant change in Wavelength Division Multiplexed (WDM) optical networks. We have proposed diverse hybrid optical amplifier configurations for the better performance of WDM optical networks. These configurations are SOA-EDFA, EDFA-EDFA and EDFA-Raman amplifier for 24 channels WDM optical networks at 10 Gbps with channel spacing of 0.8 nm. The performance of the systems is evaluated on the behalf of different parameters such as, quality factor, eye diagram, bit error rate and output power. The efforts are made to optimize these parameters. From the results, it is assessed that EDFA-Raman configuration gives superior results as compared to EDFA-EDFA configuration and SOA-EDFA hybrid optical amplifier configuration for long distance. Further it is also observed that EDFA-Raman hybrid optical amplifier configuration is suitable for high data rates up to 20 Gbps.

QoT-aware tree selection, routing, modulation, and spectrum assignment for filterless EONs over the C + L-band

Filterless optical networks (FONs) as an economical solution use passive couplers/splitters rather than expensive active filter devices. In this way, after intermediate and destination nodes, lightpaths are dropped and continued, which generates leakage signals in other links and wastes spectrum. Thus, designing efficient resource allocation in FONs by considering the leakage signals and their interfering effects is of utmost importance. On the other hand, a gradual transition from wavelength division multiplexing optical networks to elastic optical networks (EONs) is occurring due to their efficient utilization of spectrum. Furthermore, utilizing the L-band beside the conventional C-band for spectrum assignment offers a wide range of frequency resources. Therefore, in this paper, we propose an integer linear program (ILP) to solve quality of transmission (QoT)-aware tree selection, routing, modulation, and spectrum assignment problems in filterless EONs over the C+L-band. Furthermore, we provide heuristic algorithms to deal with complex large-scale networks. The performance gap of the proposed ILP and heuristic algorithms is evaluated over a small-scale (5-node) network. The results show that the ILP and heuristic algorithms have almost the same performance in terms of spectrum usage and assigned modulation format, and ILP has a slightly higher generalized signal-to-noise-ratio (GSNR) (0.23 dB or 0.8% at optimum launch power). Furthermore, the heuristic algorithms are also examined over a large-scale network (TID region A topology). The results reveal that the GSNR estimation method severely affects the performance in terms of spectrum usage, blocking, and outage. Furthermore, by using the proposed MX5 method, as long as there is a fill margin of approximately 2 dB, there is no outage or blocking over the C+L-band, up to a network throughput of 110 Tbps and conventional C-band transmission with lower throughput (i.e., 40 Tbps). Finally, our extensive numerical results provide a rule of thumb for balancing blocking, outage, spectrum usage, and the number of expensive L-band transponders by selecting the appropriate modulation assignment method.

Earthquake-Tolerant Energy-Aware Algorithm for WDM Backbone Network

Traffic on backbone communication networks is growing significantly every year. This results in an increase in both energy consumption and the carbon footprint they leave on the environment. As a response, research efforts are focused on reducing energy consumption in telecom networks. Wavelength division multiplexing (WDM) optical networks are key for addressing rising bandwidth demands in backbone networks, but this leads to a concurrent surge in energy usage. Additionally, regions with high seismic activity risk damage to backbone networks from earthquakes, causing significant bandwidth loss and service disruptions. This paper aims to reduce the energy consumption in a backbone network by implementing an algorithm that optimizes energy efficiency while preserving network connectivity and resistance to earthquake phenomena. The proposed algorithm redesigns and modifies a backbone network by deactivating the unnecessary links without affecting the network performance. The scheme is extensively evaluated through simulations using real seismic data from the Geodynamic Institute of the National Observatory of Athens, confirming earthquake resilience and energy efficiency goals, with an energy saving of up to 9% compared to existing solutions.

EDFA with power pump laser in WDM Network design of 10GBPS transmission

Wavelength Division Multiplexing (WDM) that enabled optical networks are currently widely used in current telecommunications infrastructures and are anticipated to play a significant role in next-generation networks and the future Internet, supporting a wide range of services with a wide range of bandwidth, latency, reliability, and other feature requirements. In WDM networks, the input power of an optical transmitter is crucial; as a result, this results in a good output signal at the receiver side. The purpose of this paper is to design a WDM Optical Network in terms of length and pump power. The system is simulated using Opti-System software to achieve bit error rate (BER), quality factor, and output power of EDFA through optimized fiber length and pump power. In this analysis, the BER value, Q-factor and output of the system have been evaluated between 1550 and 1552nm with 0 dBm input signal power. EDFA length of 5km, power pump value of 500mv and 980nm frequency was set as reference in this study. This system was analysed using Opti-System simulation software at 10 Gigabits per second (10GBPS) transmission system. Result have shown that, min BER value shows a very significant increase at a 9-meter length and the Q-factor was rapidly decrease. The min BER value was in range 10-11 and 10-19 and Q-factor range 6.5 to 9.1 for 200mW to 8000mW power pump.

Mitigating network adaptation and QoT prediction challenges in WDM networks

Abstract The capacity and efficiency of optical communication networks have been completely transformed by wavelength division multiplexing (WDM) technology, which allows many wavelengths to be transmitted simultaneously over a single optical fibre. Conventional QoT prediction is based on analytical models that consider physical layer characteristics including dispersion, optical power and signal-to-noise ratio. But these models frequently oversimplify complex real-world situations, which reduces their accuracy for modern high-speed WDM networks. A data-driven solution is provided by machine learning(ML), which may boost the accuracy of QoT predictions by utilising real-time measurements, historical data and a variety of network situations. The creation of a ML-based framework for QoT prediction is investigated in the current research. This research proposes an effective ML-based routing computation model that uses a non-linear autoregressive recurrent neural network (ML-RCNA-RNN) to ensure QoT for every wavelength channel in high-capacity and high-speed WDM networks. Through simulations, more accurate QoT metrics, such as bit error rate (BER) 68.42 %, QoT prediction accuracy (Q-Factor) 5.9 %, network adaption time (ms) 48.3 %, latency (ms) 0.28 % and throughput (Gbps) 14.29 %, have been obtained compared to conventional QoT predictions. These results were obtained using Gaussian noise Python simulation (GNPy). As a result, the proposed framework that makes use of GNPy demonstrates that it substantially enhances optical communication networks’ performance and dependability. This facilitates the development of high-capacity, low-latency and reliable communication infrastructure, and makes it more adaptable and able to manage the complexity of high-speed WDM optical networks while preserving signal quality in the modern digital era.

Dual-neighborhood iterated local search for routing and wavelength assignment

The minimum routing and wavelength assignment (min-RWA) problem is a classic and challenging NP-hard combinatorial optimization problem which aims to reduce the required wavelengths in wavelength-division multiplexing optical networks. In order to tackle this problem, we present a dual-neighborhood iterated local search (DN-ILS) by alternately evaluating a shift-shaking and a swap-shaking neighborhood to improve the current solution. Both neighborhoods are based on an ejection chain-based shaking (ECS) procedure, while the high-level procedures are shift moves and swap moves, respectively. These two move operators change the wavelengths of certain lightpaths, while the ECS refines routing for the related lightpaths. Experimental results on commonly used benchmark instances demonstrate that our proposed DN-ILS algorithm outperforms the best methods in the literature by improving the best known results for 35 out of 113 instances while matching the best known results for the remaining ones. The success of the shift-shaking and swap-shaking neighborhoods inspires us to apply them to other challenging optimization problems with multi-level decisions and strong constraints.

Effect of Gain Saturation on Wideband WDM Signal in PPLN-Based Optical Parametric Amplifier

The periodically poled LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> (PPLN) based optical parametric amplifier (OPA) is a technology that contributes to the construction of multi-band wavelength-division multiplexing (WDM) optical networks thanks to its wide amplification bandwidth and wavelength conversion function. In addition, the fast response of the OPA means it is unaffected by sudden changes of wavelength channels due to dynamic channel add-drop. However, such fast response leads to nonlinear signal distortion when operating in the gain saturation region. This paper experimentally investigates the conversion of gain saturation into the nonlinear amplitude distortion in a 64-Gbaud 64QAM WDM signal. We characterized the input power tolerance of a PPLN-based OPA in wideband WDM applications and found that the nonlinear amplitude distortion can be suppressed by increasing the number of WDM channels. For a 75-GHz-spacing 64-channel WDM configuration, the total input power tolerance was improved by ∼10 dB compared to a single-channel case. We also confirmed that there is almost no wavelength dependence of the effect of gain saturation on the signal distortion. These results show that PPLN-based OPAs have a wide total input power range for amplifying wideband WDM signals in terms of the nonlinear distortion.

Machine learning‐based regression models for predicting signal quality of dense wavelength division multiplexing (DWDM) optical communication network

SummaryOver the years, optical communication systems have been a significant source of fast and secure communication. However, factors like noise and mitigation error can degrade the bit error rate (BER) and quality factor (Q factor) of optical communication systems. Predicting the optimal threshold, Q factor, and BER is usually a difficult task. Therefore, in this paper, machine learning‐based linear regression, least absolute shrinkage and selection operator (LASSO) regression, and Ridge regression have been used for a dense wavelength division multiplexing (DWDM)‐based optical communication network to predict the signal quality. These techniques have been used to predict the desired BER, Q factor, threshold, and eye height of the system. To demonstrate this research concept, a DWDM‐based optical communication network of 50 km length is designed and simulated using Optisystem‐14.0. After data preparation, regression models have been developed and validated through diagnostic plots. Results show that mean square error (MSE) has a significant decline with an increase in the number of epochs for all four models. LASSO and Ridge regression have effectively resolved the issue of overfitting, which occurred in the linear regression case. Furthermore, the mean MSE plot proved the significant reduction of mean MSE in the case of LASSO regression. Results show that min BER for LASSO regression came out to be −173,627.14, providing a robust and cost‐efficient process.

Cost-Aware Optimization of Optical Add-Drop Multiplexers Placement in Packet-Optical xHaul Access Networks

This work concentrates on the problem of optimizing the cost of a passive wavelength division multiplexing (WDM) optical network used as a transport network for carrying the xHaul packet traffic between a set of remote radio sites and a central hub in a 5G radio access network (RAN). In this scope, we investigate the flexible use of optical add-drop multiplexers (OADMs) for the aggregation of traffic from a number of remote sites, where the type/capacity of optical devices—OADMs and optical multiplexers (MUXs)—is selected in accordance with the traffic demand. The approach is referred to as Flex-O. To this end, we formulate the xHaul network planning problem consisting in the joint provisioning of transmission paths (TPs) between the remote sites and the hub with optimized selection and placement of OADMs on the paths and proper selection of MUXs at the ends of the TPs. The problem formulation takes into accounts the optical power budget that limits the maximum transmission distance in a function of the amount and type of optical devices installed on the TPs. The network planning problem is modeled and solved as a mixed-integer linear programming (MILP) optimization problem. Several network scenarios are analyzed to evaluate the cost savings from the flexible (optimized) use of OADMs. The scenarios differ in terms of the availability of OADMs and the capacity of the WDM devices applied on the TPs. The numerical experiments performed in three mesh networks of different size show that the cost savings of up to between 35 and 45% can be achieved if the selection of OADMs is optimized comparing to the networks in which either single-type OADMs are used or the OADMs are not applied.

Design and development of coherent-OOFDM techniques in wavelength division multiplexing optical network for long-haul communication

Abstract Today, communication is a crucial factor and requires a high data rate for transmission with in an error-free environment, so optical communication has emerged as a best solution to high-speed transmission systems due to its higher bandwidth and higher data rates. Fiber optic transmission integrating with some modern processing and modulator techniques are applied in various areas that need transfer of data from one point to another through reducing an optical affect. Coherent optical orthogonal frequency division multiplexing is a popular technique in optical communication today because of the excessive spectral efficiency, immune to interference, tolerance of the fiber dispersion and it is long-haul application. It employs the OFDM modulation method, which is a type of multicarrier modulation in which data statistics are distributed over a large number of low-cost subcarriers and is a solution to inter-symbol interference. Inter-symbol interference is generated by chromatic dispersion in high-speed optical transmission systems, and it is a severe issue in long-haul systems in the case of higher data rates transmission. The use of standard dispersion compensating devices, such as dispersion compensating fiber, does not completely compensate for high order dispersion, which includes third-order and high dispersion effects and also increase the loses of the system because it is a fiber in itself. This study proposes introducing the concept of coherent optical orthogonal frequency division multiplexing techniques in to the wave division optical network in the case of multiple users, high data rate transmission and long-haul and ultra-long-haul optical link to reduce the optical transmission on related issues and to improve the performance of optical network. The performance of the proposed network can be evaluated by using different parameters such as signal to noise ratio, bit error rate, optical signal to noise ratio, Quality factor and eye-diagram at different distance transmission up to 8000 km by using Optisystem software.

SDN-based band-adaptive quality assurance scheme in support of heterogenous B5G services over sliceable multi-band optical networks

The rise of traffic intensive services and applications is pushing the limits of conventional single band Wavelength Division Multiplexing (WDM) optical networks. As an answer to this challenge, new data plane technologies are being investigated. Multi-band optical networks have raised as a very interesting candidate due to the potential increased capacity they offer thanks to the exploitation of multiple bands of the optical spectrum. Considering the whole telecom ecosystem, multi-band optical networks will coexist with other technological segments (e.g., Radio Access Network (RAN)) with the aim of provisioning services across the end-to-end infrastructure. With the advent of 5G and beyond 5G (B5G) architectures, novel provisioning paradigms are taking preponderance, such as the case of network slicing, which represents a radical paradigm change with respect to legacy business and provisioning models. As such, proper solutions for supporting network slice provisioning and runtime maintenance at the data plane are required. With this in mind, in this paper we present a control and orchestration architecture for the configuration and maintenance of network slices in multi-band optical networks, in support of B5G end-to-end services. Indeed, quality assurance and maintenance at all levels is seen as a cornerstone in B5G architectures. Thus, proper mechanisms adapted to the nature of the underlying sliceable multi-band data plane are required to ensure the quality of deployed slices. In this regard, we also present a novel band-adaptive protection scheme which takes advantage of the properties of the multi-band data plane so as to enhance the robustness of slices against quality degradations. We showcase the provisioning and maintenance of multi-band optical network slices by means of an experimental demonstration in a real testbed deployed at our premises. In addition, we evaluate the performance of the proposed band-adaptive protection scheme for slice quality assurance in front of other strategies by means of extensive simulation analysis in larger network scenarios.

Wide-Sense Nonblocking Multicast in WDM Optical Linear Array and Ring Networks with 3-Length Extension Under Longest Link First Routing

The modern scientific growths in optical networks based on wavelength division multiplexing (WDM) are more attractive to satisfy the high bandwidth requirements of the modern internet infrastructure. Moreover, they potential to satisfy the future bandwidth requirements.WDM optical networks act as the backbone for telecommunication and high-performance communication networks. Multicast communication is the simultaneous transmission of data from one source node to many destination nodes available in the network over wavelength division multiplexing. It is extensively deployed in high performance computing and communication networks. In this article, a linear array and ring networks are extended by directly linking all nodes which are separated by two intermediate nodes with additional fibers which is referred as linear array and ring network with 3-length extension. The wavelength allotment methods are proposed to realize one-to-many communication over wavelength division multiplexing optical linear array and ring with 2-length extension under longest link first routing and the minimum wavelength number needed is determined. The minimum wavelength number needed to support for the extended linear array is reduced approximately by 20% when compared with that of a linear array network and for the extended unidirectional ring is reduced approximately by 25% when compared with that of a unidirectional ring network. And also, for the extended bidirectional ring the minimum wavelength number is reduced approximately by 33% when compared with that of bidirectional ring network.

Spectrum-Entropy-Minimized Routing and Spectrum Allocation in IP over Mixed-Fixed/Flex-Grid Optical Networks

Mixed-Fixed/Flex-Grid Optical Networks (MFGONs) are a new paradigm that emerged during the brown-field migration from fixed-grid Wavelength Division Multiplexing (WDM) optical networks to flex-grid Elastic Optical Networks (EONs). Based on the flex-grid, we can accommodate IP traffic directly to the optical layer by configuration. Considering the different granularities of spectrum resources and complex constraints in MFGONs, it is difficult to apply Routing and Wavelength/Spectrum Allocation (RWA/RSA) algorithms proposed in either fixed-grid or flex-grid optical networks. This paper first proposes two concepts, i.e., Link Spectrum Compactness (LSC) and Radiancy of Nodes (RoNs), to evaluate different scenarios of candidate paths for the end-to-end requests in MFGONs. Then, based on these two concepts, a Spectrum Entropy (SE) model is proposed in MFGONs. Here, the SE is the metric that combines LSC and RoNs to judge the fragmentation of network resources, and the value of SE is treated as the cost of candidate paths during the RSA operation. Finally, an SE-minimized RSA algorithm in MFGONs is designed. Simulation results prove that the proposed algorithm can effectively reduce the Bandwidth Blocking Ratio (BBR) and increase the revenues for upgrading the nodes compared to the state-of-the-art RSA algorithm. Particularly, the performance improvement is more obvious for highly connected networks.

Challenges and Enabling Technologies for Multi-Band WDM Optical Networks

The ever increasing capacity demand on optical networks and the slowdown of improving spectral efficiency lead to the solution of utilizing more wavelength band in existing optical fibers. More and more operators will extend from C band to C&#x002B;L bands, or plan to deploy C&#x002B;L systems, and in future they may utilize more of other bands. This paper firstly discusses different optical layer architectures for multi-band system. Using optical components that can natively support multi-band is attractive to us, because in this way the multi-band system can be planned and operated similarly with the single-band system, which is customer friendly and potentially more economical. We address mainly three technical challenges in this paper. The first one is the wide-band fiber optical amplifier (OA). After a short review of recent research progress, we propose a hybrid erbium-doped fiber (EDF) and bismuth-doped fiber (BDF) based OA approach, and demonstrated single-stage amplification over 100 nm in extended C&#x002B;L bands. The second challenge is the optical cross connect based on wavelength selective switch (WSS). It is not trivial to realize a C&#x002B;L-band WSS while preventing the key optical parameters (filtering bandwidth, loss, channel isolation, etc.) to be degraded. We analyze different technical schemes, and propose an optical design based on an LCoS with a large panel size and a high-dispersion diffraction grating. The optical design and simulation on a 2&#x00D7;35 WSS reveals this approach can support 100-nm extended C&#x002B;L spectrum and is promising for commercialization. The third challenge is the SRS induced WDM channel power inequality, which is more severe for multi-band system. We propose a solution by using OAs with a novel optical spectrum processor (OSP). Simulation and experiment showed that the power of the WDM channels can be equalized on a per span basis, which can prevent accumulation of stimulated Raman scattering (SRS) induced wavelength division multiplexing (WDM) channel power transfer and can meanwhile keep the optical signal to noise ratio (OSNR) of WDM channels well equalized.

Characteristic's analysis of associative switching system

This paper introduced new method and model of telecommunication switching system design which can be applied to wavelength-division multiplexing (WDM) optical networks, circuit-switching networks or virtual channel/path connections in an asynchronous transfer mode (ATM) networks. Modern data switching systems such as electronic private branch exchange (PBX), routers and switches include switching matrix which are constructed in the form of bipartite graphs. In such systems, the issues of requests’ processing are considered from the queuing theory point of view. Associative switching systems are fundamentally new structures, therefore it is necessary to develop adequate methods for their throughput determination. Article covered matters of throughput determination basics of an associative switching system and the obtained formulas used for state probability calculation of switching modules and system throughput.

Network-state-dependent routing and route-dependent spectrum assignment for PRMLSA problem in all-optical elastic networks

The advent of Elastic Optical Networks (EON) has led to significant improvements in optical network spectrum utilization when compared to Wavelength Division Multiplexing Optical Networks. However, the EON brought challenges to be explored, notably the Power, Routing, Modulation Level and Spectrum Assignment (PRMLSA) problem. This article aims to explore techniques for the PRMLSA problem, being developed two strategies named Shortest and Least Allocated (SLA) Path and Route-Based Spectrum Assignment (RBSA), which, respectively, include the link power spectral density inspection dynamic for routing and a physical layer factor (distance traveled) for Spectrum Assignment. Furthermore, a simplified version of the Adaptive Power Assignment (APA) [1] algorithm is presented, in which a power value between the minimum necessary and the maximum allowed is assigned to the signal. The simultaneous use of the SLA and RBSA algorithms resulted in locks of up to 0.00132%, being more than 10 times lower than the 0.0164% of the Shortest-Path and First-Fit algorithms. While the simplification of the APA resulted in 18.38% of the execution time of its respective original version, but with an increase in the blocking probability, which went from 0.016% to 0.031%, despite still being below conventional techniques, as the Constant Power Assignment strategy.

A high-reliability optical network architecture based on wavelength division multiplexing passive optical network

A high-reliability optical network architecture based on wavelength division multiplexing passive optical network

Auxiliary-Graph-Based Energy-Efficient Traffic Grooming in IP-Over-Fixed/Flex-Grid Optical Networks

Due to the development of broadband access technologies including FTTx and 5G, the traffic in metro and core networks is forecasted to be more dynamic. To support this dynamicity, flex-grid elastic optical networks (EONs) have started to become prolific over the past few years. During the migration from the legacy fixed-grid wavelength division multiplexing optical networks to flex-grid EONs, a transition technology called the fixed/flex-grid optical network has become popular. In such fixed/flex-grid networks, the energy consumption caused by serious capacity mismatch between variable IP traffic and the different optical channel capacities is significantly high to be ignored. In fact, energy-efficient traffic grooming (i.e., to aggregate multiple fine-grained IP flows and map them onto a lightpath) is a challenge in IP-over-fixed/flex-grid optical networks because co-existing fixed-grid and flex-grid nodes have different traffic grooming ability and energy consumption models. To overcome the challenge, we propose an auxiliary-graph-based energy-efficient traffic-grooming (EETG) algorithm in IP-over-fixed/flex-grid optical networks for the first time. The construction of an auxiliary graph (AG) model for each connection request is one of the core steps. The well-designed weight-assignment scheme of the AG establishes the relationships between traffic grooming operations and specific energy consumption models. The final traffic grooming operations are undertaken based on the calculated weight-minimized path. The simulation results show that the EETG algorithm achieves 1) the least energy consumption compared with the state-of-the-art traffic grooming algorithms under the non-blocking scenario; and 2) achieves the tradeoff between energy consumption and blocking probability under the blocking scenario.