Question

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One of the major advantages that SDH networks have over traditional PDH networks is the standardization of its technology. Before the advent of SDH, ITU-T O.171 existed for test equipment used in testing PDH systems. In the early days of SDH, ITU-T O.171 was also used as the basis for designing SDH test equipment. However, it wasn't until ITU-T O.172 was introduced that the ITU addressed test equipment specifications for testing SDH optical signals from 52 Mb/s to 2.5 Gb/s and for electrical signal rates of 52 Mb/s and 155 Mb/s. The objective of ITU-T O.172 is to
clearly define test equipment requirements for verifying,to
ITU-TG-series recommendations, that SDH network equipment: functions properly in the presence of defined (allowable) levels of jitter and/or wander does not generate excessive levels of jitter and/or wander The following key elements of ITU-T O.172 are used to establish test equipment standards: an input phase tolerance test for test equipment more precise definition of jitter measurement filters than in ITU-TO.171 the use of concatenated payloads filled with PRBS to emulate the worst case test scenario reduced intrinsic jitter levels for test equipment pointer sequence generation as per ITU-T G.783 jitter generation levels to exceed ITU-T G.825 (jitter tolerance for network equipment) It is worth noting that SDH tributary interfaces include those operating at PDH rates.

Answer 1

其中一项主要优势， SDH网络已超过传统的PDH网络的标准化技术。前来临的SDH ， ITU - T的o.171存在测试设备中使用的测试的PDH系统。在成立之初的SDH ， ITU - T的o.171还采用了并以此为基础设计的SDH测试设备。然而，直到ITU - T的o.172介绍说，国际电联处理测试设备的规格，测试SDH光信号从52 MB /秒至2.5 Gb / s的和为电信号率52 MB /秒和155 MB的/秒。客观的ITU - T o.172是
明确界定测试设备的要求，核实，
国际电联的TG -一系列的建议， SDH网络设备：在职能，妥善在场的定义（允许）各级抖动和/或漫步，不产生过多的各级抖动和/或漫步下列要素的ITU - T澳一七二顷用于建立测试设备标准：一期投入为耐受性试验测试设备更精确的定义，抖动测量的过滤器比在ITU - to.171使用级联的有效载荷充满prbs学习最坏的情况下测试的情况减少的固有抖动各级为测试设备指针序列一代％的ITU - T g.783抖动生成的水平超过了ITU - T g.825 （抖动容差为网络设备） ，这是值得注意的是， SDH的支流接口包括那些经营的PDH利率。