Remigiusz Rajewski

The Architecture and Strict-Sense Nonblocking Conditions of a New Baseline-Based Optical Switching Network Composed of Symmetrical and Asymmetrical Switching Elements

In this paper, we introduce a new multiplane optical switching fabric structure based on a baseline type switching network. The new structure is built from symmetrical and asymmetrical optical switching elements. This new architecture can be extended to structures of greater size (it means capacity as a number of inputs and outputs). To compare different types of switching architectures, we define the cost of an appropriate structure as the number of its passive and active optical elements. Generally, structure with smallest number of these elements constitutes a cheaper solution. We also introduce a strict-sense nonblocking conditions for the proposed multiplane structure and compare them with an optical baseline multiplane switching networks of the same capacity. We show that for most capacities of the switching network, the new multiplane architecture is a cheaper solution than the multiplane baseline network even when the number of planes in the new architecture is greater than the number of one planes in the baseline structure — cost of the whole new structure expressed as the number of passive and active optical elements is fewer than baseline network of the same capacity.

Strict-Sense Nonblocking W-S-W Node Architectures for Elastic Optical Networks

The paper considers optical node architectures for elastic optical networks. They use switching fabric topologies which are similar to the three-stage Clos switching networks. These architectures employ wavelength switching in the first and the third stages, and space switching in the second stage, and are also called W-S-W switching fabrics. In elastic optical networks, the optical spectrum is divided into frequency slot units. One frequency slot unit uses 12.5 GHz of bandwidth and an optical path may use m adjacent frequency slot units. Such connection is called an m-slot connection. For each architecture, strict-sense nonblocking conditions are derived and proved for such m-slot connections. The number of center stage switches and the number of frequency slot units in interstage links are calculated and evaluated. The considered architectures are compared to each other. When the maximum number of frequency slot units that may be used by one connection, is not too high, these architectures can be implemented in practice.

The log_2{N-1} Optical Switching Fabrics

In this article, we introduce a new space-division optical switching fabric architecture based on baseline switching networks. The new structure is built from optical switching elements (OSE) 2 × 2, 3 × 3, 2 × 3, and 3 × 2. The new structure is called the log2 N-1 switching network and consists of fewer numbers of active and passive optical elements than traditional baseline switching networks composed of symmetrical OSEs. In the paper, we investigate space-division multiplane strict-sense and rearrangeable log2 N-1 nonblocking switching networks and compare these with space-division multiplane baseline switching networks. The new structure has lower cost than other architectures for strict-sense nonblocking (SSNB) conditions and for rearrangeable (RNB) networks with odd number of stages. For RNB networks, when the number of stages is even, the cost of the multiplane log2 N-1 optical switching network is equal to or higher than traditional networks.

Strict-sense nonblocking space- wavelength-space switching fabrics for elastic optical network nodes

In elastic optical networks, a connection may occupy a frequency slot that spreads over m adjacent frequency slot units (FSUs). Such connection (called m-slot connection) also must be realized in optical nodes used in these networks. The paper considers two architectures of the three-stage switching fabric that can be used in such network nodes. The switching fabric applies space switching in the first and the third stages and wavelength switching in the second stage [the space-wavelength-space (S-W-S) switching fabric]. For both architectures, denoted by SWS1 and SWS2, we derived and proved the strict-sense nonblocking conditions when m-slot connections are set up. The number of center stage wavelength switches is calculated and evaluated. The switching fabrics are compared with the strict-sense nonblocking wavelength-space-wavelength (W-S-W) switching fabric. It is shown that the number of center stage switches does not depend on the number of FSUs available in input and output fibers but only on the maximum number of FSUs, which can be used by one connection and the number of input/output fibers in one input/ output space switch. When the number of FSUs in one connection is, for instance, limited to 5, only 11 center stage switches are needed for nonblocking operation in one of the architectures. Moreover, for switching fabrics with a greater number of maximum FSUs in one connection and a greater number of FSUs in one input or output fiber, the S-W-S switching fabrics can be practically realized, unlike the W-S-W switching fabric.

The rearrangeable nonblocking conditions in the multi-MBA(N, e, 2) switching network

In this paper the rearrangeable nonblocking conditions for the MBA(N, e, 2) switching fabric were described. The cost of the new switching network, calculated as the number of active and passive optical elements, was presented as well. This cost was compared also with the cost of the typical baseline switching fabric of the same capacity. When the size of optical switching elements grows, the new switching network is a cheaper solution. When size of such elements is lower, the new structure is more expensive solution.

The New Banyan-Based Switching Fabric Architecture Composed of Asymmetrical Optical Switching Elements

In this paper, we propose the new architecture of the optical switching fabric which is based on the baseline switching network. Traditional baseline switching networks are composed of 2 × 2 (or d × d) switches. The new architecture considered in this paper is constructed from 2 × 2, 3 × 3, 2 × 3 and 3 × 2 switching elements. We show, that the proposed architecture requires less crosspoints than the traditional baseline architecture. We assumed an optical application, where semiconductor optical amplifiers are used as the optical switching elements. The proposed structure requires less number of active elements as well as passive optical splitters and combiners than the traditional baseline switching fabric. It also contains one stage fewer than the banyan network (therefore we called it the log2 N -1 switching fabric), which results in lower signal losses, distortions, and crosstalk.

Optical datacenter networks with elastic optical switches

Four variants of the optical data center network architecture (DCN1 — DCN4) based on optical circuit switching and elastic optical switching elements are proposed. For each variant theoretical limits for non-blocking operation have been derived and proved. The proposed networks are also compared in terms of the required number of switching elements. Our results show that variant DCN1 is more appropriate for very small data centers with tens of racks with servers, while variant DCN4 requires much fewer switching elements in data centers with hundreds or thousands of such racks.

The Strict-Sense Nonblocking Multirate Switching Network

This paper considers the nonblocking conditions for a multirate switching network at the connection level. The necessary and sufficient conditions for the discrete bandwidth model, as well as sufficient and, in particular cases, also necessary conditions for the continuous bandwidth model, were given. The results given for in the discrete bandwidth model are the same as those proposed by Hwang et al. (2005); however, in this paper, these results were extended to other values of , , and . In the continuous bandwidth model for , the results given in this paper are also the same as those by Hwang et al. (2005); however, for , it was proved that a smaller number of vertically stacked switching networks are needed.