SDH and SONET Analyzers 718 Network Test Instrumentation in Software

Encode Code 128 Code Set B in Software SDH and SONET Analyzers 718 Network Test Instrumentation

Choosing an Analyzer This section deals with general concerns and provides a brief guide to important features and specifications in each of the major areas of analyzer use Synchronous analyzers are used throughout the life cycle of a network element, from initial design to installation and maintenance within a network The features that are important in an analyzer vary with its area of use The following section deals with five main areas of use and the relevant feature sets Table 301 at the end summarizes the chapter

Research and development (R&D) covers a large area of testing Testing at this stage is usually manual and extremely rigorous and exhaustive, concentrating as it does on a complete understanding of the component/PCA/NE under test Broadly speaking, two types of testing occur, functional and parametric The parametric tests (pulse mask analysis, bit error rate tests, etc) usually are confined to the early development stages of a product, ie the design of specific circuits, PCBs, and basic ASICs A synchronous tester required in this area usually is a parametric tester with some (limited) ability to construct and transmit synchronous signals In addition, some simple alarm generation also might be necessary Two types of R&D functional testing can be identified, leading-edge and steadystate The leading-edge tester deals with the standards as they evolve, providing the new services as soon as they are defined For this type of investigation it is necessary that all the bytes in the frame structure can be accessed, altered, and tested The ability to perform rigorous and exhaustive tests on all parts of the structure is vital in leading-edge R&D applications, where new capabilities are constantly being addressed Figure 3011 shows a typical instrument used for leading-edge design, the HP 75000 Series 90 SDH/SONET analyzer Based on the VXI standard, the instrument is modular, flexible, and capable of accessing all the EOC bytes In addition, it has sophisticated stressing and capture capabilities that facilitate the rigorous testing required The user of steady-state R&D testing tends to be behind the evolving standards, concentrating on the well-established aspects of the standards, building second-generation equipment that often is cheaper and/or more compact than the leading-edge or firstgeneration devices Cost then starts to become a more important factor in the choice of instrument The range of bytes that might need to be accessible usually is a small, well-defined subset of the entire structure, so a less sophisticated tester probably is called for Often the steady-state user is designing gear in an area where the standards are well-defined and the behavior of the protocol is understood; the designer is looking for a good source of synchronous signals to do the basic day-to-day testing on an engineer s bench Typically the steady-state design lab will have access to a high-end or leading-edge instrument for final detailed testing

The next stage after (or towards the end) of the design cycle is QA and verification testing This involves comprehensive testing to ensure correct function of an NE to

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Figure 3011 Typical leading-edge R&D analyzer (courtesy Hewlett-Packard)

its design specifications, often coupled with rigorous climatic testing The criteria for instruments used in this application are similar to those for R&D The complexity of the tests often is lower, however, concentrating on testing the device against a set of limits rather than fully characterizing its performance In addition, since test development time for QA is often a critical part of many projects, the programmability of a instrument and the ability to operate in an automated environment also are very important