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Method for transparent aggregation of arbitrary client signals by a SONET/SDH multiplexer

IP.com Disclosure Number: IPCOM000010117D
Publication Date: 2002-Oct-23
Document File: 4 page(s) / 247K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for transparent aggregation of arbitrary client signals by a synchronous optical network/synchronous digital hierarchy (SONET/SDH) multiplexer. Benefits include improved performance, improved ease of manufacturing, improved design flexibility, and improved power performance.

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Method for transparent aggregation of arbitrary client signals by a SONET/SDH multiplexer

Disclosed is a method for transparent aggregation of arbitrary client signals by a synchronous optical network/synchronous digital hierarchy (SONET/SDH) multiplexer. Benefits include improved performance, improved ease of manufacturing, improved design flexibility, and improved power performance.

Background

        � � � � � High-speed digital transmission systems are often tasked to transport a number of client signals through a single high-capacity medium using time division multiplexing (TDM). A simplified block diagram illustrates the conventional approach� (see Figure 1). Two multiplexer/demultiplexer stages concentrate 64 parallel data lines of a layer-2 transport system to one line for transmission through a fiber.

        � � � � � The four client signals in this example are output by the layer-2 devices, such as a SONET framer or an optical terminal node (OTN) digital wrapper. The output is through 4 X 16 synchronous data lines. The output is then multiplexed by 16 by the four first-stage multiplexer devices. A second multiplexer stage processes the output by four to the 1-bit serial transmission format. An issue with this solution is the synchronicity of the four streams (which may run at 10 Gbit/s) that are required by the second stage multiplexer for error free take-over of the data. Unacceptable amounts of phase variations may appear at the outputs of the four first-stage multiplexers, due to different temperature, supply voltage, process, or aging variations. The result may be most critical and may even result in an impossible system design.

        � � � � � One way to make system design easier is to lower the rate at the synchronous inputs of the second stage multiplexer using a by-sixteen device instead of a by-four device (see Figure 2). This alternative has the same disadvantage as the first approach. The data input for the second stage multiplexer is the output from four different stage-one multiplexer devices.

General description

        � � � � � The disclosed method uses a modified multiplexer/demultiplexer function of a SONET/SDH layer-2 device to aggregate arbitrary, but synchronous, client signals for transparent transport through a common medium.

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved performance due to 16 x 4-to-1 multiplexer and 16 x 1-to-4 demultiplexer integrated into one package replacing up to 8 conventional physical-layer devices

•        � � � � Ease of manufacturing due to the reuse/modification of an already integrated hardware function

•        � � � � Improv...