External Atomic Clock (Gm); External Gnss Receiver (Gm) - Safran WR-ZEN Series User Manual

5.2 General Timing Management
ciplined by a single reference and forwards its timing to the down layers through
all the other ports.
5.2.1.2

External Atomic Clock (GM)

Web GUI selection: GM: ext AC
It is recommended to use this preset when the device is configured to be the
Grand-Master in the timing network and is disciplined using an Atomic Clock as
external reference.
Here, Atomic Clocks means that a very stable oscillator based on hyperfine trans-
ition (e.g, Caesium) that provides very low daily uncertainties (e.g., 1 ns/day) is
combined with a GNSS receiver to remove its slow drift using averaging meth-
ods. For telecom, this combination is also known as ePRTC and typically provides
a UTC representation accurate within 10 ns or less. Moreover, in order to guar-
antee the best timing performance (phase noise & determinism) the automatic
alignment of the PPS output onto the PPS input has been disabled.
5.2.1.3

External GNSS Receiver (GM)

Web GUI selection: GM: ext GNSS
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The primary timing source is provided using an external atomic clock ref-
erence through the front-panel 10 MHz and 1PPS inputs (Grand-Master).
All timing ports (i.e., wr0-wr1) are configured as WR masters.
Clock accuracy is announced below or equal to 25 nanoseconds.
Alignment of PPS_in VS PPS_out must be done manually (within pico-
seconds)
PPS only needed at startup
Caution: 10 MHz + PPS signal calibration: When using this preset, the
PPS must always keep the same delay in respect to the 10 MHz sig-
nal. The user can use the GM Offset field to compensate this fixed
delay.
The primary timing source is provided using an external GNSS receiver ref-
erence through the front-panel 10 MHz and 1PPS inputs (Grand-Master).
All SFP ports (i.e., wr0-wr1) are configured as WR masters.
Clock accuracy is announced below or equal to 100 nanoseconds.
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5 WR-ZEN Series User Manual Rev. v5.1