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A Simplified All-Optical Switch Architecture

IP.com Disclosure Number: IPCOM000124526D
Original Publication Date: 2005-May-20
Included in the Prior Art Database: 2005-May-20
Document File: 2 page(s) / 99K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The switching speed of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. It is a present task to speed up the optical switches: In a Virtual Wavelength Path (VWP) all-optical cross-connects consist of a (M*W)*(M*W) strictly non-blocking switch architecture, followed by an array of fixed wavelength converters whose role is to avoid collisions which would otherwise occur whenever two input ports with the same wavelength are routed to the same output fiber. AII-optical switch architectures for VWP-OXC (VWP-Optical Cross Connect) become very large and impractical even for moderate numbers of fibers, M, and wavelengths, W. The switch size can be reduced by designing it to support only a suitably chosen subset of the permutations supported by a conventional VWP-OXC switch. This concept is totally distinct to that of a multistage rearrangement of a non-blocking switch. A conventional VWP-OXC utilizes a strictly non-blocking (M*W)*(M*W) switch which supports all possible (M*W)! (Factorial) permutations between the input ports and the corresponding output ports. Thus, this switch supports routing any input port both to a given output fiber and to a given wavelength converter (as long as the number of input ports routed to the same output fiber does not exceed the number of wavelengths available on the fiber). In others words, it is possible to route any input port towards any output fiber, and choose the output wavelength at the same time.

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A Simplified All-Optical Switch Architecture

Idea: Jorge Castro, PT-Amadora; João Pedro, PT-Amadora

The switching speed of electronics cannot keep up with the transmission capacity offered by optics. All-optical switch fabrics play a central role in the effort to migrate the switching functions to the optical layer. It is a present task to speed up the optical switches:

In a Virtual Wavelength Path (VWP) all-optical cross-connects consist of a (M*W)*(M*W) strictly non- blocking switch architecture, followed by an array of fixed wavelength converters whose role is to avoid collisions which would otherwise occur whenever two input ports with the same wavelength are routed to the same output fiber. AII-optical switch architectures for VWP-OXC (VWP-Optical Cross Connect) become very large and impractical even for moderate numbers of fibers, M, and wavelengths, W.

The switch size can be reduced by designing it to support only a suitably chosen subset of the permutations supported by a conventional VWP-OXC switch. This concept is totally distinct to that of a multistage rearrangement of a non-blocking switch.

A conventional VWP-OXC utilizes a strictly non-blocking (M*W)*(M*W) switch which supports all possible (M*W)! (Factorial) permutations between the input ports and the corresponding output ports. Thus, this switch supports routing any input port both to a given output fiber and to a given wavelength converter (as long as the number of input ports routed to the same output fiber does not exceed the number of wavelengths available on the fiber). In others words, it is possible to route any input port towards any output fiber, and choose the output wavelength at the same time.

A simpler switch is proposed that can route all possible sets of W input ports to any given output fiber, without supporting all (M*W)! permutations as the conventional VWP switch. The simplified switch is smaller because each input port may only be routed onto a restricted subset of the wavelength converters (ports) available on the output fiber. Therefore, the switch supports only a subset of the permutations supported by the conventional VWP architecture.

This simplified switch design can be implemented with less (or simpler) switching elements, compared to the conventional VWP switch architecture. However, the price paid for this simplification is that it may be necessary to rearrange previously routed connections in order to route a new one to the desired output fiber. Otherwise, the performance of the simplified VWP switch is similar to that of the conventional VWP switch: in dynamic traffic conditions, the simplified switch supports the same traffic load as the conventional VWP switch, if rearranging same earlier connections is permitted. If the traffic is static, i.e. given a priori, the performance of both the switch architectures is absolutely identical.

The benefit of the simplified VWP switch is that it can be considerably smaller than its tradition...