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Newsletter: GL Announces T1 E1 Jitter and
Pulse Mask Measurement Solutions

Welcome to another February 2009 issue of GL's Newsletter providing information and insight into our Jitter Measurement and Pulse Mask Testing solutions.

Jitter Measurement

Jitter along with wander and frequency drift are major impairments of clocks in synchronous systems. Jitter is the time discrepancy between the time of arrival of a clock pulse and its theoretical arrival time. Jitter arises from a number of sources, including aging of clock circuits, thermal and loading effects, Doppler shifts, and de-multiplexing from higher bit rate data streams.

GL's Jitter Measurement module allows evaluation of jitter on either a tick-by-tick or a cumulative basis. Technically, cumulative jitter is of primary importance as network equipment must cope with the cumulative jitter. However, tick-by-tick measurements are also presented in this module.

Since clocks under test can have arbitrary clock rates, it is customary to talk about jitter in terms of the time duration of a single clock pulse. This time interval is referred to as a "Unit Interval" or UI. For T1 systems operating at 1.544 Mbps, 1 UI equals 647 nanoseconds. For E1 systems operating at 2.048 Mbps, 1 UI equals 488 nanoseconds. UI durations for higher rate bit streams are proportionately smaller.

Important Jitter Measurement Features

  • Easy, accurate, jitter measurements for T1 E1 signals (Universal T1 E1 cards only)
  • Option to select T1 or E1 port for monitoring and jitter frequency range
  • Supports One-Shot capture, Repeated Capture, and Save options
  • Results of measurements in *.CSV file
  • Supported on Windows 2000/XP/Vista
  • Jitter generation (coming soon)

For further information, please refer to Jitter Measurement web page.

Pulse Mask Compliance Testing

It is quite common for T1 E1 signals, within a central office environment or an enterprise telecom room, to NOT meet pulse mask requirements due to interference, too long or short cable lengths, improper impedances, or simply poor transmitter design. In such cases, pulse mask compliance is very useful in diagnosing problems.

GL's Universal T1 E1 Cards have pulse shape measurement capability. Software has been developed to determine if the pulse shape fits within a "pulse mask" as specified by standards ITU G.703 and ANSI T1.102-1993. The software is available in both visual and tabular formats. Tabular formats are convenient for automation and scripted test environments.

GL's solution provides pulse mask compliance testing using Pulse Mask Display for both T1 and E1 applications.

Important Pulse Mask Compliance Features

  • Plots the pulse measured within a predefined template
  • Compares the incoming T1 E1 pulses against the pulse mask display
  • For T1 pulses, the X-axis measures time in unit intervals (UI); for E1 pulses, the X-axis measures time in nanoseconds (ns)
  • Y-axis measures the normalized amplitude in volts
  • Standards compliant with ITU G.703 and ANSI T1.102-1993
  • Software is available in visual and tabular formats

For further information, please refer to Pulse Mask Testing web page.

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