Ah Heng You

A five-order mode converter for multimode waveguide

A numerical model of five-order mode converter that converts the order of modes in an integrated-optic multimode waveguide is proposed. Such a structure is useful in optical guiding wave devices for mode control and mode shuffling. The dimensions and index profile of the device are well within the capabilities of the state of the art of integrated optics technology. We have successfully optimized the structural design of the device for propagation loss of less than 13.1 dB at an operating wavelength of 1.55 /spl mu/m. A cascaded form of the five-order mode converter is also proposed for selective mode conversion without the need of restructuring the connection within the device.

Optimal placement of wavelength converters in WDM networks using particle swarm optimizer

The introduction of wavelength converters in all-optical networks can reduce the blocking probabilities of calls. The main contribution of this paper is that we introduce a novel search algorithm namely particle swarm optimizer in finding the optimum solution to the converter placement problem. Experiments have been conducted to demonstrate the effectiveness and efficiency of the proposed algorithm. The computed results show that it is more cost effective to introduce additional wavelength channel in a single fiber than placing more wavelength converters.

Wavelength Converters Placement in All Optical Networks Using Particle Swarm Optimization

Placement of wavelength converters in an arbitrary mesh network is known to be a NP-complete problem. So far, this problem has been solved by heuristic strategies or by the application of optimization tools such as genetic algorithms. In this paper, we introduce a novel evolutionary algorithm: particle swarm optimization (PSO) to find the optimal solution to the converters placement problem. The major advantage of this algorithm is that does not need to build up a search tree or to create auxiliary graphs in find the optimal solutions. In addition, the computed results show that only a few particles are needed to search the optimal solutions of the placement of wavelength converters problem in an arbitrary network. Experiments have been conducted to demonstrate the effectiveness and efficiency of the proposed evolutionary algorithm. It was found that the efficiency of PSO can even exceed 90% under certain circumstances. In order to further improve the efficiency in obtaining the optimal solutions, four strategic initialization schemes are investigated and compared with the random initializations of PSO particles.

Buffering management schemes for optical variable length packets under limited packet sorting

This paper studies several buffering strategies for optical packet switching (OPS) under limited packet sorting. Three schemes, which are able to sort newly arrived packets based on packet’s length as well as capability of finding the minimum buffer occupancy, are analyzed and compared. Results show that all three proposed schemes could improve OPS performance considerably in terms of probability of packet loss (PPL) and probability of information loss (PIL). In addition, the simulation results show that not all the newly arrived packets need to be sorted in order to obtain minimum packet loss probability. Since the amount of packets and thus the packet processing time is significant in OPS, it is possible that not all the packets can be processed using one of the buffering strategies. An important finding of this paper is that if only 10% of the packets are sorted, the PPL is comparable to the minimum packet loss value obtained when 100% of the packets are sorted.

Performance evaluations of multi-layers ring network architecture

Performance evaluations of the multi-layers ring network architecture with unicast/multicast function have been done recently by using non-parametric approach. It was claimed that the proposed architecture outperforms the conventional point-to-point multi-layers architecture in terms of the link cost and interface cost. This paper further investigates the impact of the traffic to the nodes in such architecture with unicast capability through optical packet switching simulations. It is found that there are serious packet losses at layer 3 if switches capacity are same at all levels; the required number of wavelengths/optical buffers increases exponentially in order to maintain a given packet loss rate when more layers exist in the architecture. Therefore, it shows that too many layers architecture may affect the networks performances.

Cascaded five-fold mode-order switching device

A numerical cascaded five-fold mode-order switching device has been simulated for selective mode-order conversion in cases where an arbitrary type of mode-order conversion is desired without the need of reconfiguring the connections within the device.

Correction to "A Five-Order Mode Converter for Multimode Waveguide"

A numerical model of five-order mode converter that converts the order of modes in an integrated-optic multimode waveguide is proposed. Such a structure is useful in optical guiding wave devices for mode control and mode shuffling. The dimensions and index profile of the device are well within the capabilities of the state of the art of integrated optics technology. We have successfully optimized the structural design of the device for propagation loss of less than 13.1 dB at an operating wavelength of 1.55 /spl mu/m. A cascaded form of the five-order mode converter is also proposed for selective mode conversion without the need of restructuring the connection within the device.

Buffering controls for IP packets in optical packet switching

This paper investigates several buffering schemes for variable IP packets length in optical packet switching (OPS). Three new schemes with sorting abilities according to the packets length as well as the capability of finding the minimum buffer occupancy are introduced in order to compare with the common round-robin scheme. The computed results show that there is a trade off between packets drops probability and information loss probability for the investigated schemes. It can be concluded that the bigger the Hust parameter of self-similar traffic the higher probabilities for the packets to drop and information loss but vice versa when more wavelengths are used.