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Method to Improve the Protection Switching for Optical Transport Networks

IP.com Disclosure Number: IPCOM000018929D
Original Publication Date: 2003-Sep-25
Included in the Prior Art Database: 2003-Sep-25
Document File: 9 page(s) / 140K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

The purpose of this invention is to improve the business opportunity for protection switching in the optical layer and the applicability of integrated OXC (Optical cross Connect) -applications. The field of this invention is the technical realization of shared protection switching in optical networks at competitive cost, using leveraging existing signaling methods. The current solution to protect network connections for the OTN (Optical Transport Network) according to the recommendation of the International Telecommunications Union ITU Rec. G.709 is quite cost-intensive. For analysis and application scenarios in the network, a reference network architecture is used (Figure 1). Optical channels, fiber or lambda of a Wavelength Division Multiplexing (WDM) system, interconnect the n sites of the reference model. The optical channels do not share the same risk of failure, i.e. they are physically located in disjoint ducts and are not elements of the same Shared Risk Link Group (SRLG). For example if we assume n = 3, there would be six OTN-multiplexer (MUX) involved in the network scenario. The OTN-multiplexer is the equipment terminating the optical channel. The basic functionality of the MUX is to aggregate m low data rate client signals to one high data rate line signal transported on the optical channel, when m > 1. In general, the new method is applicable to networks where several sites build a mesh or ring.

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© SIEMENS AG 2003 file: 2003J07016.doc page: 1

Method to Improve the Protection Switching for Optical Transport Networks

Idea: Arnold Monitzer, US-Boca Raton, FL

The purpose of this invention is to improve the business opportunity for protection switching in the optical layer and the applicability of integrated OXC (Optical cross Connect) -applications. The field of this invention is the technical realization of shared protection switching in optical networks at competitive cost, using leveraging existing signaling methods. The current solution to protect network connections for the OTN (Optical Transport Network) according to the recommendation of the International Telecommunications Union ITU Rec. G.709 is quite cost-intensive.

For analysis and application scenarios in the network, a reference network architecture is used (Figure 1). Optical channels, fiber or lambda of a Wavelength Division Multiplexing (WDM) system, interconnect the n sites of the reference model. The optical channels do not share the same risk of failure, i.e. they are physically located in disjoint ducts and are not elements of the same Shared Risk Link Group (SRLG). For example if we assume n = 3, there would be six OTN-multiplexer (MUX) involved in the network scenario. The OTN-multiplexer is the equipment terminating the optical channel. The basic functionality of the MUX is to aggregate m low data rate client signals to one high data rate line signal transported on the optical channel, when m > 1. In general, the new method is applicable to networks where several sites build a mesh or ring.

Today the availability of the connections in the network is improved by protecting the optical channels. The standard of availability is usually defined in the Service Level Agreement (SLA) between the carriers and their clients. If the carrier does not meet the required availability for a certain connection the revenue from this connection will be reduced dramatically. However, achieving higher availability always comes along with higher capital expenditures.

At present the protection is conducted by the client using the Optical Channel Protection (OCP) card. The concept of the OCP is summarized in Figure 2:

- The optical splitter distributes the received optical signal of the client port (c) to the working (w) and the backup channel (p).

- The received optical power is measured at the working channel (w) and if it becomes too low, the optical selector switches to the optical signal of the backup channel (p).

The symbol representing the OCP is shown in Figure 2c (selector switched to w) and Figure 2d (selector switched to p). The application of the OCP card in the reference network (Figure 1) is shown in Figure 3. For the protection of a single optical channel, two additional multiplexer (MUX2n+1, MUX2n+2), 2m additional OCP cards (OCP1, ..., OCP2m) and an additional backup path have to be installed (grey in Figure 3). Figure 3 shows the principle for a single chan...