M. Meenakshi

Wavelength assignment for all-to-all broadcast in WDM optical linear array with limited drops

All-to-all broadcast is to disseminate a unique message from each node to every other node. This is a fundamental problem in multiprocessor systems and telecommunication networks that need to collect information about other nodes in the network regularly in order to manage network resources efficiently. In this paper, a novel wavelength assignment method is proposed to establish all-to-all broadcast in a linear array network. The network model is an all-optical network, in which a message from source node can be dropped (or split) only at a limited number of destination nodes along a light path due to power loss of dropping optical signals. The minimum number of wavelengths required to establish all-to-all broadcast is also derived for a linear array network.

Wavelength Assignment for All-to-All Broadcast in Wavelength Division Multiplexing Optical Ring

Abstract A novel wavelength assignment method is proposed for a bidirectional WDM ring network and the minimum number of wavelengths required to support all-to-all broadcast is determined. The new method can assign each wavelength directly and simultaneously to a group of non-overlapping connections on an N-node ring without the aid of any table or matrix. The presented wavelength assignment method is much faster than other direct methods with explicit formulas previously reported for WDM ring network.

All-to-all broadcast in optical WDM networks under light-tree model

This paper addresses the problem of wavelength requirements for all-to-all broadcast communication in wavelength division multiplexed optical networks. The network model is an all-optical network, in which a message can be split and dropped to all destination nodes along a light-tree. A tight bound on the minimum number of wavelengths required to establish all-to-all broadcast communication for various topologies is presented. The optimal routing and wavelength assignment algorithms for all-to-all broadcast to achieve the minimal number of wavelengths are also described for these topologies

An Efficient Wavelength Assignment for all-to-all Broadcast in Optical WDM Hypercube Network

Wavelength-division multiplexing (WDM) optical networks provide huge bandwidth by allowing multiple data strams transmitted simultaneously along the same optical fiber, with each stream assigned a distinct wavelength. An important issue in optical WDM networks is to minimize the number of wavelengths required for communication. All-to-All broadcast is a fundamental communication application on computer/communication networks. In this paper, we provide the method of assigning wavelengths for all-to-all broadcast communication in optical WDM hypercube network without light splitters under e-cube routing algorithm. We also find the minimum number of wavelengths required to support all-to-all broadcast communication.

Dynamic Lightpath Establishment in WDM Optical Networks Under the Constraints of Transmission Impairments

This paper considers the physical layer transmission impairments while establishing a call in a wavelength-routed optical network. The impact of different routing and wavelength assignment (RWA) algorithms on the crosstalk performance of a 4x4 mesh-torus and a 15-node mesh network has been studied. This paper considers both switch-induced crosstalk and the crosstalk induced by the multiplexers and demultiplexers. A fast and accurate approach is employed to study the impact of gain saturation of Erbium-doped fibre amplifiers (EDFA’s) on the received signal quality of a 15-node network of interconnected rings. Previous works have approximated the measured EDFA gain curve by curve fitting approach. In this work, EDFA gain is numerically determined using the fast and accurate approach. The crosstalk and EDFA gain saturation can lead to poor received signal quality at the destination node. This results in increased receiver bit error rate (BER). This implied that some of the routes will deliver a signal quality which is unsatisfactory. To ensure that no resources are wasted on those connections which cannot deliver an acceptable signal quality, this paper uses an event-driven simulation which incorporates on-line BER calculations. A call is accepted only if the BER at the destination node is less than 10−12; otherwise it is rejected.

A Study of Four Wave Mixing Nonlinear Effect on Various Fiber Types in DWDM Optical Systems

Dense Wavelength Division Multiplexing (DWDM) transport systems are highly attractive in today’s telecommunication scenario since they offer large capacity with a small number of channels and also achieve high spectrum efficiency. Fiber nonlinearities can have a serious impact on the performance of these systems. The presence of nonlinearities causes the channel capacity to be a nonmonotonic function of the input signal strength. The information throughput can be increased by using dispersion shifted fiber having minimum loss and zero dispersion at 1.55 µm wavelength and Er-doped optical fiber amplifiers in the fiber links. But low dispersion and high intensity of the signal launched enhance the four wave mixing, a third order non-linear effect. Due to this low dispersion and high intensity of light pulse, frequency mixing is made in an efficient manner and new wavelength are generated. This is called four wave mixing penalty. If one of the generated new wavelength is equal to signal wavelength in the DWDM modulated carrier, the interference or cross-talk is produced and that will reduce the signal to noise ratio at the receiver side. To the best of the author’s knowledge and with reference to the literature we have presented in this paper, how the inter modulation products are generated due to four wave mixing effect and are observed experimentally using single mode fiber also simulation is made with dispersion shifted fiber for two channel and sixteen channel wavelength division multiplexed transmission system. In addition, FWM power (cross-talk) is evaluated and compared for three major types of fibers like single mode fiber, dispersion shifted fiber, non-zero dispersion shifted fiber.

Optimal Wavelength Converter Placement in Wavelength-Routed Optical Networks by Simulated Annealing

Wavelength-routed all-optical networks have emerged as a popular architectural solution for wide area networks and are being conceived for future broad-band communications. Call connection probability in such networks depend on the number of WDM wavelengths employed and on the capability for wavelength conversion at network nodes. Equipping all the network nodes with wavelength converters to reduce the blocking probability is not a cost effective solution due to the high cost of wavelength converters. Hence only some of the nodes are to be equipped with wavelength converters. The objective of this paper is to address the optimal placement of wavelength converters among the network nodes. Here “placement” refers to providing a network node with wavelength conversion capability. This paper uses simulated annealing to determine the location of the converters in order to achieve minimum blocking probability. It is observed that this method significantly reduces the number of blocking probability calculations and has been applied to a six hop path and to the ′14 nodes NSFNET. The results are verified with the published literature. This method achieves optimal and near-optimal solutions at low computational expense and minimum programming requirement.

Suppression of Four Wave Mixing Crosstalk Components — a Comparative Study Between Genetic Algorithm and Optical Orthogonal Codes

Increase in the data rate of fiber optic communication systems limited due to the nonlinear effects like Self phase modulation(SPM), Cross phase modulation(XPM) and Four wave mixing(FWM). Many investigations are carried out to mitigate these effects. In multi channel systems. Four wave mixing (FWM) in optical fibers induces channel cross talk and possibly degrade system performance. An opticalorthogonal code is the family of(01) sequence with good auto and cross correlation properties. It has been found in the literature that the FWM crosstalk components can be suppressed by the unequal spacing of the multiplexed channels. This unequal and equal spacing of the channel and frequency allocation is done using optical orthogonal spreading codes and the results are compared with the channel allocation using the Genetic algorithm (GA) approach for the first lime to the best of author’s knowledge. The optical orthogonal code frequency allocation technique scheme is advantageous than the GA approach in terms of reduced optical bandwidth requirements and more number of channels with null FWM crosstalk points. The Entire simulation work in this paper is carried out using MATLAB7 and SIMULINK tool box.

Performance Measurement of Various Modulation Formats in the Presence of Dispersion and Non Linear Effects for WDM Optical System

Increase in the data rate of fiber optic communication system is limited due to dispersive and nonlinear effects of the fiber medium. In this paper for the first time to the author’s knowledge we have estimated the optimal length of dispersive compensating fiber which is determined by varying the DCF length to obtain high Q factor for various input power levels. Also we have simulated 16 and 32 DWDM channels for the data rate of 40 Gb/s and determined the Q factor for various modulation formats for the non linear dispersive fiber.