The Centre for metrology and accreditation in Finland (MIKES,
http://www.mikes.fi ) is evaluating White Rabbit for time & frequency
GM hardware is SPEC + DIO.
Input 10 MHz and 1 PPS signals to grand master.
Note that the 1 PPS signal serves only to mark which rising-edge of the
10 MHz waveform is considered the inter-second boundary.
After a "mode gm" command to lock the PLL to the external 10 MHz signal
the PTP time is reset starting at 1970.
To set the correct integer number of seconds we use a python script
An experiment to measure the stability of time-transfer over short (<10
GrandMaster locked to UTC-MIKE
500m fiber to WR-switch, 500m fiber back to WR-Slave
Slave 1PPS output measured compared to GrandMaster input timebase
Measurement with Agilent 53230A (20ps)
Data was collected over ca 30 days. The result is similar to that of
Lipinski2012, showing no drift and a 1/tau dependence.
Long distance time transfer
MIKES has set up a White Rabbit link between two PCs that are connected
with a 1000 (one thousand!) kilometer link.
This work is a collaboration between MIKES and CSC (http://www.csc.fi) -
IT Center for Science Ltd that operates Funet (the Finnish National
Research and Education Network).
The White Rabbit console reports a mean round-trip-time (RTT) delay of
10.4 ms with a daily variations of ca +/- 40 ns. 10.4 ms corresponds to
a ca 2000 km round trip, assuming a refractive index of 1.5. The WR
protocol is compensating for the daily variations, but this could not
yet be verified as both points are physically spaced at a 567 km driving
This experiment shows that the White Rabbit hardware and protocols are
much more flexible than the original design goal for use at maximum
distance of ten kilometer. Also the fact that the designs are "Open",
made that MIKES could easily replace the original SFP lasers by longer
GrandMaster (Espoo): SPEC + DIO
SFP 1000BASE-BX TX1490nm/RX1310nm (came with starter-kit)
By reading the WR time from shared memory (see specmem.c in spec-sw) and
writing the time to a specific place&format in shared memory (where NTP
looks) it is possible to use WR as a refclock for NTP.
This allows placing NTP servers anywhere in your WR network that
distribute WR time.