The REFIMEVE network primarily distributes two signals generated in LTE :
This signal comes from a laser stabilised on an ultra-stable Fabry-Perot cavity, whose frequency is actively controlled relative to the LTE clocks. The relative uncertainty of the signal’s frequency is on the order of 10-14–10-15 under routine conditions and potentially down to a few 10-17. This uncertainty is not degraded during propagation through the network; it is maintained up to the end users.
The frequency noise of this signal is extremely low: relative frequency fluctuations are on the order of 10-15 for 1-second measurement times. However, during propagation, this excellent stability is slightly degraded, particularly for Fourier frequencies above approximately 10 to 100 Hz. As a result, the signal received by users has a linewidth ranging from less than 1 Hz to a few kHz, depending on the location within the network.
These signals are distributed using the WhiteRabbit method. The uncertainty of the synchronisation signal is at most 10 ns, and the residual fluctuations are on the order of a nanosecond. The relative uncertainty of the radio-frequency reference is 10-14 under routine conditions and is not degraded by the REFIMEVE network; the residual relative frequency fluctuations are on the order of 10-12 for 1-second measurement times and 10-15 over a day.
For more information on the current and future performance of the distributed signals and optical links, see the T-REFIMEVE page.
For more information on the signals distributed and generated at LTE, see the LTE website.
For more information on the distribution of the optical signal and the compensation of propagation noise, see the Optical Frequency Transfer page.
