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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) / 99K

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...