Wavelength Division Multiplexing Networks Research Articles

A Multi-core Shared Tree Algorithm Based on Network Coding for Multi-point Optical Multicast

AbstractWith the growth of multi-point to multi-point multicast applications, the optical network bandwidth resource consumption is increasing rapidly. It attracted more and more researchers to improve the limited wavelength bandwidth utilization for multicast applications in wavelength division multiplexing (WDM) networks. In the paper, a multi-core shared multicast tree algorithm based on network coding is proposed to minimize the fiber link stress. The proposed algorithm includes three processes: searching the core node candidate set excluding core node loop path, selecting the core nodes from the convergence matrix based on heuristic algorithm, and constructing the multi-core nodes shared trees. The convergence matrix based on the heuristic method is constructed for selecting the core nodes from candidate core node set. To improve the limited wavelength utilization, we introduce network coding into the shared tree to compress the transmitting information. The simulation results show that the proposed algorithm’s performance is better than the existing algorithms’ performance in terms of link stress and balance degree.

Performance analysis of optimized non-zero dispersion shifted fiber without amplification and without dispersion compensation for wavelength division multiplexing optical networks

Performance analysis of optimized non-zero dispersion shifted fiber without amplification and without dispersion compensation for wavelength division multiplexing optical networks

Fifty-five km reach, bidirectional, 400 Gb/s (40 \times 10 Gb/s), channel-reuse DWDM–PON employing a self-wavelength managed tunable laser

We experimentally demonstrate a channel-reuse bidirectional 10 Gb/s/λ long-reach dense wavelength-division multiplexing passive optical network (DWDM-PON) and an optical beat-noise-based automatic wavelength control method for a tunable laser used in a colorless optical network unit (where λ=wavelength). A 55 km, bidirectional, 400 Gb/s (40×10 Gb/s) capacity channel-reuse transmission with 100 GHz channel spacing is achieved. The transmission performance is also measured with different optical signal to Rayleigh backscattering noise ratios and different central wavelength shifts between upstream and downstream in the channel-reuse system.

Converged ultra-wideband and multi-level wired signal downstream transport over single wavelength in wavelength-division multiplexing passive optical network

Converged ultra-wideband and multi-level wired signal downstream transport over single wavelength in wavelength-division multiplexing passive optical network

Analysis on the Effect of Adopting Green SLA on Optical WDM Networks

This paper analyzes the effect of Green Service Level Agreement (GSLA) on resource efficiency and emission reduction of wavelength-division multiplex (WDM) optical networks governed by Generalized Multi-Protocol Label Switching (GMPLS). Green routing mechanisms may use more resources in serving equal number of connection requests in optical networks, which makes them less favorable for Internet and infrastructure providers. This work shows that the usage of green and hybrid routing mechanism is in fact more resource efficient than using traditional non-green routing methods by simply choosing the greenest route. The amount of greenness of routes in optical networks is requested through GSLA mandating service providers to provide routes for connection requests that are being powered ON by at least certain amount of green energy such as solar energy.

Long-reach bidirectional 320 Gb / s ( 32 × 10 Gb / s ) channel-reuse dense wavelength division multiplexing passive optical network employing self-wavelength managed tunable laser

We demonstrate a channel-reuse bidirectional 10-Gb/s/λ long-reach DWDM-PON and an optical beat noise-based automatic wavelength control method for a tunable laser used in a colorless optical network unit. 100-GHz channel spacing 55- and 100-km full-duplex bidirectional 320 Gb/s ( 32 × 10 Gb/s ) capacity transmissions are achieved without and with optical amplification. Transmission performance is also measured with different optical signal to Rayleigh backscattering noise ratios and different central wavelength shifts between upstream and downstream in the channel-reuse system.

125-km Long Cavity Based on Self-Seeded RSOAs Colorless Sources for 2.5-Gb/s DWDM Networks

The laser behavior of reflective semiconductor optical amplifier self-seeded sources is investigated. 2.5-Gb/s transmission is realized with optical cavities of 10, 26, 100, and 125 km for access and metropolitan networks, realizing the longest amplified self-seeded external cavity laser. Moreover, Gigabit Ethernet, common public radio interface, and 2.5-Gb/s transmissions are experimented using amplified self-seeded reflective semiconductor optical amplifier wavelength division multiplexing passive optical networks systems. A field trial setup is exploited to test the system performance in terms of reach and optical budget.

Minimizing Blocking Probability for the Multicast Routing and Wavelength Assignment Problem in WDM Networks: Exact Solutions and Heuristic Algorithms

Given a sparse splitting wavelength division multiplexing (WDM) network and a set of available wavelengths, we investigate the problem of provisioning a set of multicast requests simultaneously with the objective of minimizing the blocking probability. Two blocking models are taken into account: full blocking probability and partial blocking probability. As the problem is NP-hard, we propose an integer linear programming (ILP) formulation with two variants (each for a blocking model) to search for the optimal solution and several efficient adaptive heuristic algorithms to compute approximated solutions. In particular, instead of using light-trees, both ILP and heuristics use light-hierarchy, a recently proposed optimal route under sparse splitting configurations. Extensive simulations reveal that our adaptive algorithms are able to compute near-optimal solutions, and they outperform static approaches under both blocking probability models. The results also show that it is more advantageous to provision multiple multicast communications with light-hierarchies, since they are able to accommodate more requests and destinations compared to the light-tree solutions.

High Output Power and Burst Extinction Ratio λ-Tunable ONU Transmitter Using Burst-Mode Booster SOA for WDM/TDM-PON

This paper proposes a high output power and high burst extinction ratio wavelength (λ)-tunable optical network unit (ONU) transmitter for long-reach and high-splitting ratio wavelength-division multiplexing and time-division multiplexing passive optical network (WDM/TDM-PON) systems. Our λ-tunable ONU burst-mode transmitter (B-Tx) utilizes a simply configured burst-mode controlled booster semiconductor optical amplifier (SOA) that employs the pattern effect mitigation technique of gain peak detuning. A high output power and burst extinction ratio are successfully achieved at all upstream wavelength channels, over +10.0 dBm and 66.0 dB, respectively. This burst extinction ratio performance satisfies the ONU requirement for a 64-split WDM/TDM-PON with crosstalk penalty of better than under 0.1 dB. Moreover, the pattern effect is greatly mitigated and 40 km transmission penalty of under 0.8 dB is achieved. We successfully demonstrate over a 41 dB loss budget and 40 km reach λ-tunable WDM/TDM-PON without an optical-amplifier-based PON repeater.

Design analysis of flattop all-fiber asymmetric interleaver

A novel all-fiber interleaver consisting of a three-stage cascaded Mach–Zehnder interferometer (MZI) is presented. Based on a comprehensive analysis, a mathematical description is provided. To achieve a flattop wavelength response, a design process is adopted to determine the optimum coupling-coefficient-angle values according to finite impulse response (FIR) digital filter theory. A set of coupling-coefficient-angles of fiber couplers were obtained. Furthermore, these optimum coupling-coefficient-angle values were exploited to fabricate an interleaver with flattop response within the passband in the experimental, so these optimum values are validated. The theoretic analysis and the experimental results indicate that the flattop passband in odd channels and even channels could be obtained. 3dB passband in odd channels and in even channels are asymmetric, and the 3dB passband is more than the 60GHz passband and 30GHz passband, for transmission speed of 40Gb/s and 10Gb/s, respectively. The channel isolation of the interleaver is more than 35dB. The tolerance characteristics of the splitting ratios are favorable. Our design and analysis should be useful in the realization of flattop all-fiber asymmetric interleaver for deployment in dense wavelength division multiplexing (DWDM) networks of high spectral efficiency.

Throughput Comparison Between 50-GHz and 375-GHz Grid Transparent Networks [Invited

With the introduction of Nyquist pulse shaping, it is possible to transmit a channel in a spectral window close to its baud rate. To increase the overall network spectral efficiency, the most promising solution seems to be the reduction of the channel spacing. Standardization bodies have proposed a flexible grid with 12.5 GHz of granularity. Hence, 100-Gb/s signals can be transported in a 37.5-GHz grid network. While a 37.5-GHz channel spacing brings an ideal extra-throughput of 33% compared to a 50-GHz spacing, this value ignores filtering-induced impairments occurring when a narrower channel spacing is adopted. In this paper, we numerically investigate the filtering penalty stemming from optical filters and its implications on the extra-throughput provided by 37.5- versus 50-GHz grid wavelength division multiplexing (WDM) networks for two different networks with two different traffic distributions. We show fully transparent network scenarios where the ideal 33% extra-throughput of 37.5-GHz channel spacing is drastically reduced or even vanishes because of filtering penalties.

Electroabsorption-modulated widely tunable DBR laser transmitter for WDM-PONs.

We present an InP based distributed Bragg reflector (DBR) laser transmitter which has a wide wavelength tuning range and a high chip output power for wavelength division multiplexing passive optical network (WDM-PON) applications. By butt-jointing InGaAsP with 1.45 µm emission wavelength as the material of the grating section, the laser wavelength can be tuned for over 13 nm by the DBR current. Accompanied by varying the chip temperature, the tuning range can be further enlarged to 16 nm. With the help of the integrated semiconductor optical amplifier (SOA), the largest chip output power is over 30 mW. The electroabsorption modulator (EAM) is integrated into the device by the selective-area growth (SAG) technique. The 3 dB small signal modulation bandwidth of the EAM is over 13 GHz. The device has both a simple tuning scheme and a simple fabrication procedure, making it suitable for low cost massive production which is desirable for WDM-PON uses.

Long-reach OFDM WDM-PON delivering 100 Gb/s of data downstream and 2 Gb/s of data upstream using a continuous-wave laser and a reflective semiconductor optical amplifier.

This paper presents a long-reach orthogonal frequency division multiplexing wavelength division multiplexing passive optical network (OFDM WDM-PON), a system capable of delivering 100 Gb/s of data downstream and 2 Gb/s of data upstream on a single wavelength. The optical sources for downstream data and upstream data are a continuous-wave laser at a central office and a reflective semiconductor optical amplifier (RSOA) at each optical network unit.

Line Shape Effects in the Operation of Thulium and Erbium Doped Fiber Amplifiers

This work describes the effect of Gaussian line shape on the comparison of the amplification characteristics (gain) and the Noise figure (NF) of the Thulium and Erbium in the host materials which the Yttria Alumina-Silica glass. The gain using this host material covers the range 1.45-1.65 μm. Thulium-doped fiber amplifiers operated in the region of wavelength (14801510 nm) which is called S-band. The main pump source is 1.04 and 1.55 pm which creates population inversion between 3F4 (upper laser level) and 3H4 (lower laser level), and Erbium- doped fiber amplifiers operated in the region (1510-1650 nm) which is called L -band with the pump wavelength 980 nm. It is found that the erbium doped yttria-alumina silicate fiber amplifier exhibits a maximum gain of 40.3 dB at the central wavelength 1540 nm and minimum noise figure 14 dB, but the broadening in the gain curve is 20 nm. Also it is found that the thulium doped yttria-alumina silicate fiber amplifier exhibits a maximum gain of 27.5 dB at the central wavelength 1467 nm and minimum noise figure 2.5 dB, with the broadening in the gain curve is 41 nm. Gain flatness was investigated and the results strongly confirm the feasibility of using this hosts' glass doped with Thulium in practical ultra large capacity wavelength division multiplexing networks.

A Cross-Layer Optimization and Design approach under QoS constraints for green IP over WDM networks

Energy consumption of communication networks is growing very fast due to the rapidly increasing traffic demands. It is important and valuable to find a way to save power for such networking systems. In this paper, we propose a Cross-Layer Optimization and Design (CLOD) approach to improve the energy efficiency of Internet Protocol (IP) over Wavelength Division Multiplexing (WDM) backbone networks under QoS constraints. CLOD makes use of the skew spatial distribution (i.e. 80–20 law) of traffic demands to construct the virtual topology of IP layer with a consideration of the cross-layer resource constraints. Also, CLOD takes advantage of the constraint-based routing to satisfy the QoS constraints in terms of allowed maximum hop count and allowed maximum link utilization. Taking into account the connection between base network design and network operation, CLOD dimensions the base network by using pattern of network operation and optimizes network power consumption by reconfiguring network to adapt traffic variation and the available resources. Simulation results indicate that CLOD can save power significantly and achieve near energy-proportional networks. In addition, an analysis on trade-off performance between the hop count and power consumption is given.

A Novel Access and Control System in a WDM Passive Star-Coupled Network for Optical Backhaul

A passive star-coupled (PSC) optical wavelength division multiplexing (WDM) network is considered a promising candidate for optical backhaul particularly in densely populated urban areas. In this paper, we present the access and control system design for wireless backhaul transmission over a PSC wavelength division multiple access (WDMA) network. We employ an in-band control-signal technique, providing dedicated control slot access, and the length of the control slot is minimized and unconstrained by the length of a data slot, aiming at offering thorough control information and maximizing the system performance. A packet-by-packet, reservation-based, and frame-basis medium access control (MAC) scheme is presented. The MAC scheme ensures round-robin scheduling to flexibly transmit data packets within a data frame by simply adopting two initial variables. The simulation results show that the network achieves exceptionally high system performance when each node is equipped with only one tunable transmitter and one fixed-tuned receiver for uniform destination traffic scenarios. In a client/server traffic scenario, only the server node (which receives an additional proportion of the entire network traffic) is upgraded by replacing the fixed-tuned receiver with a fast tunable receiver; thus, exceptionally high delay-throughput performance is maintained, and the most cost-effective solutions are proposed.

Electrical filter-based and low-complexity DPSK coherent optical receiver.

Direct-detection of differential phase shifted keying (DPSK) optical signals is implemented either by ad hoc optical filtering or one-bit delayed optical interferometers. We show a coherent receiver where the filtering is performed in the electrical domain after down-converting the incoming signal to the baseband or to an intermediate frequency. This can be particularly advantageous whenever optical filters cannot be used or when extremely narrow filtering (sub-GHz) would be required [for example ultra-dense wavelength division multiplexing (WDM) passive optical networks]. Electrical filters can be realized more accurately than their optical counterpart. In addition, in a coherent receiver, this operation is colorless and avoids digital signal processing. We show experimentally this reduced complexity receiver and compare it with the classical one based on the delay and multiply block.

On methodologies to estimate optical-layer power consumption and cost for long-haul WDM networks with optical reach constraint

This paper deals with the methodologies to obtain the estimates of optical-layer power consumption and cost for long-haul optical networks using wavelength-division multiplexing (WDM) with IP-over-WDM and IP-over-MPLS-over-WDM network settings. Such optical networks generally employ wavelength routing at intermediate nodes and are known as wavelength-routed optical networks (WRONs). In WRON-based long-haul networks, optical reach (OR) of a transponder represents the maximum distance over which its optical signal can travel without any optical/electrical/optical regeneration and plays a significant role in deciding the power consumption and cost of the optical layer. In IP-over-WDM network setting, IP routers are directly interfaced with WRON and bandwidth requests are equal to the lightpath capacity. In IP-over-MPLS-over-WDM network setting, IP routers are interfaced with WRON via MPLS routers and bandwidth requests arrive as label-switched paths, which are generally lower than the lightpath capacity. We examine the above networks with mixed-OR nodes (transponders in each WRON node having different OR values but all transmitting at 10 Gbps) and fixed-OR nodes (transponders in each WRON node having same OR value and 10 Gbps transmission rate). In this investigation, two types of control planes are considered, namely unified control plane and isolated control plane. The network with unified control plane supports automated and dynamic resource provisioning for both short-term and long-term bandwidth requests. The study on nonautomated network using isolated control plane considers resource provisioning only for long-term bandwidth requests. Simulation-based network provisioning is carried out using C++, considering appropriate traffic models, OR constraints, node configurations and network architectures. The results of our simulations indicate in general how OR of the transponders can influence the total network cost and power consumption in optical layer. Overall, the nonautomated networks with mixed-OR configuration are found to save power and offer lower cost with respect to fixed-OR configuration, while the automated networks with mixed-OR configuration can save power while the cost increases with respect to fixed-OR option.

Multi-objective design of an FBG sensor network using an improved Strength Pareto Evolutionary Algorithm

To improve the multiplexing capability is a key issue in designing a wavelength division multiplexing (WDM) fiber Bragg grating (FBG) sensor network. In this paper, we present a novel FBG sensor network design based on Pareto-based multi-objective optimization technology. In contrast to conventional WDM network, the proposed network model permits the spectral response to overlap each other. The multi-objective function is established by taking two objectives into account. One objective is to minimize the total source bandwidth occupation of the sensor system to improve the multiplexing capability, and the other is to minimize the overlap degree of spectra to reduce the wavelength measurement error. The improved Strength Pareto Evolutionary Algorithm (SPEA2) is applied to search for the so-called Pareto front. One appropriate solution is selected from the non-dominated solutions to determine the Bragg wavelength assignment. Numerical results show that the proposed approach is effective in saving the bandwidth occupation and maintaining the measurement accuracy simultaneously.

Wavelength division multiplexing quantum key distribution network using a modified plug-and-play system

This paper proposes and analyzes a multi-user wavelength division multiplexing- quantum key distribution (WDM-QKD) network that employs a modified plug-and-play system; this system employs a multi-wavelength laser diode to generate wavelength pulses for Bobs and utilizes a single phase modulator to modulate the returned pulses for all users. BenefittingfromthetimedelayanddelaylineinBobs,thereturnedpulsesremainindependent of Rayleigh backward scattering caused by strong pulse signals. Numerical simulations and results show that the key rate per user maintains a high level compared with a point-to- point link, because the communications between Alice and four Bobs can be carried out simultaneously.