Chapter 3
High Accuracy Timing
Common test applications
T-BERD/MTS/SC Timing Expansion Module User Manual
Page 26
22112315, Rev. 004
July 2017
When you configure the TEM Module, you can indicate the maximum acceptable drift
while operating the module in holdover mode; the module will then estimate the time
remaining before the oscillator drifts to an unacceptable level, and provide the time
remaining in the Oscillator results category. For details, see
“Oscillator Results” on page 58
.
Common test applications
The following sections describe common test applications that require a high accuracy
timing reference such as the TEM Module.
Precision time protocol (PTP) measurements
Precision time protocol (PTP) is an industry-standard protocol (based on IEEE 1588v2)
that enables the precise transfer of frequency and time to synchronize clocks over
packet-based Ethernet networks. The PTP protocol synchronizes the PTP local slave
clock on each PTP network device with a PTP system Grandmaster clock. Therefore,
it is important to be able to accurately characterize the one way delay of the
Sync,
Follow_Up, Delay_Req
, and
Delay_Resp
messages between a grandmaster and
slave clocks.
PTP Delay
To accurately measure PTP delay, you must either use two precisely synchronized
Viavi Ethernet test instruments that are optioned and configured for PTP testing, or one
test instrument synchronized to a PTP Master (for example, a Grandmaster or
Boundary Clock).
TEM Modules can be used to synchronize 5800v2s to a high accuracy timing reference.
The synchronized instruments will tag outgoing PTP packets with timestamps. Both
instruments will recognize received PTP packets, and use the timestamps carried
within the packets to measure delay.
NOTE:
Operating the module with an
active reference signal
(or in the case of
GNSS, a connected GNSS antenna and accurate bias setting) is always
preferable to operating the module in holdover mode, even if the module’s
rubidium oscillator is finely tuned.
NOTE: 1 PPS Reference Signal Input
If you are not using a TEM, and you are using
a different source of high accu-
racy timing
(for example, a GPS receiver), the cable used on the Multi Access
SMA Timing Cable Adapter to input the signal varies depending on the 5800v2
instrument’s software version. Signal input connections for these applications
are provided in the
Ethernet, IP, TCP/UDP, Fibre Channel, and IP Video Testing
Manual
or the
PDH, SONET, SDH, NextGen, and OTN Testing Manual
.
