Preparing To Test; Understanding Synchronization Requirements; Atp-Gps Test Packets - Viavi T-BERD MTS 5800 Getting Started Manual

Chapter 4 Basic Testing

Preparing to test

Preparing to test

Before testing, Viavi recommends:
• Verifying that you have the correct cables, connectors, transceivers, or adapters
required to connect to the circuit.
• Determining whether you need to synchronize near and far end instruments to a
high accuracy timing reference before beginning the test.
• Determining whether a high accuracy timing reference is required for precise
measurements and analysis.

Understanding synchronization requirements

Some test applications will provide more accurate measurements and test results if
near and far end instruments are precisely synchronized using external high accuracy
timing references.
• The MSAM, CSAM, and 5800 can use optional, external CDMA receivers or the
optional TM4-4 GPS receiver to ensure that both instruments are synchronized,
providing measurements that are accurate within +/- 10 us. Instructions for
synchronizing test instruments using optional CDMA or GPS receivers are
provided in this manual.
• The 5800v2/100G, and 5882 can use an optional Timing Expansion Module
(TEM), to ensure that both instruments are synchronized per the same timing
reference and provide measurements that are accurate within +/- 10 ns. Instruc-
tions for synchronizing 5800v2/100G and 5882 test instruments using the optional
TEM Modules are provided in the Timing Expansion Module User Manual that
shipped with your TEM.
GPS is increasingly being used as a timing reference because it available almost every-
where and provides a common reference between various field locations. CDMA and
GPS receivers provide an accurate Time of Day (ToD) signal and 1 Pulse per Second
(PPS) signal, which, when averaged over a long time period, provide very precise
signals that can be used to create common timestamps and provide a reference clock
for instruments performing precise measurements.
When using GPS to synchronize timing on your test instruments, each instrument must
be equipped with the same type of receiver (CDMA or GPS).

ATP-GPS test packets

When your test instrument is synchronized to GPS time via the optional CDMA or
TM4-M GPS receiver (or via the optional TEM module), it tags outgoing Acterna Test
Packets (ATP) with GPS timestamps. The timestamps are required for accurate one
way delay, wander, and 1588v2 PTP, PDV, and Master-Slave delay measurements.
The receiving, synchronized instrument recognizes these packets and uses them when
performing the measurements.
Page 90
T-BERD/MTS/SC Getting Started Guide
22046537, Rev. 016 March 2018