R.I. Balayev, A.V. Naumov, A.N. Malimon
FSUE “VNIIFTRI”, Mendeleevo, Moscow region, Russia;
balaev@vniiftri.ru
Al’manac of Modern Metrology № 4 (40) 2024, pages 32–42
Abstract. The use of the modems with dual pseudo-random noise (DPN) signals in the high-precision comparison system of time scales via 300 km fiber-optical communication line with one intermediate optical amplifier is considered.
To assess the measurement error when comparing time scales, a two-way counter transmission of time and frequency signals encoded by DPN modems from one highly stable source — the hydrogen maser of GET 1-2022 — was carried out on an optical carrier. The use of one source excluded the presence of mutual frequency drift of the compared sources in the measurement results. The measurements were carried out both when transmitting counter-coded signals over same 300 km fiber line and when transmitting counter-coded signals over two different 300 km fiber lines. When transmitting coded signals along a single line, optical circulators were included at its ends to separate counter-propagating signals. The experimental results of the measurements performed are presented. Estimates of the type A uncertainty are given when performing comparisons on 300 km lines with one intermediate optical amplifier.
For the first time, it has been experimentally shown that a system with DPN modems implementing TWOTFT method can provide, with a 300 km fiber line and one intermediate optical amplifier, the performance of time scale comparisons with an uncertainty of type A not exceeding 6 ps over a daily averaging interval. Obtained results compared with previous TWOTFT experiments based on using of SATRE modems.
Keywords: comparison of time scales of remote time and frequency standards, fiber-optic lines, TWOTFT, additional tone modulation.
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