A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th Decimal Place

Abstract

Optical clocks show unprecedented accuracy, surpassing that of previously available clock systems by more than one order of magnitude. Precise intercomparisons will enable a variety of experiments, including tests of fundamental quantum physics and cosmology and applications in geodesy and navigation. Well-established, satellite-based techniques for microwave dissemination are not adequate to compare optical clocks. Here, we present phase-stabilized distribution of an optical frequency over 920 kilometers of telecommunication fiber. We used two antiparallel fiber links to determine their fractional frequency instability (modified Allan deviation) to 5 × 10(-15) in a 1-second integration time, reaching 10(-18) in less than 1000 seconds. For long integration times τ, the deviation from the expected frequency value has been constrained to within 4 × 10(-19). The link may serve as part of a Europe-wide optical frequency dissemination network.

Experimental realization of an optical second with strontium lattice clocks

“…20). The parallel development of optical fiber links [26][27][28] allows the dissemination of an optical frequency over long distances with a negligible added noise. With such a link, the possibility of comparing two remote OLCs has been demonstrated 29 recently.…”

Transfert de fréquence par fibre optique en métrologie

“…Nous avons ensuite démontré une liaison optique de 540 km utilisant le réseau Internet [22]. En Allemagne, le Physikalisch-Technische Bundesanstalt (laboratoire national de métrologie, à Braunschweig) et le Max-Planck-Institut für Quantenoptik (à Garching, près de Munich) viennent de réaliser une liaison optique d'une longueur record de 920 km en utilisant une liaison fibrée dédiée [23]. Ces avancées technologiques récentes ont ainsi démontré la faisabilité d'un réseau sur longue distance pour des applications métrologiques.…”

Frequency and time transfer for metrology and beyond using telecommunication network fibres

“…2) and demonstrated a 172-km link using recirculation in the same fibres [23]. Following these pioneering results, several groups worldwide have initiated experiments on optical links [24,27,28,[30][31][32][46][47][48].…”

“…In the last decade, several experiments in Europe, USA and Japan have explored the limits of this method, paving the way for a new generation of ultra-stable optical networks [18,[21][22][23][24][25][26][27][28][29][30][31]. A groundbreaking frequency transfer has been demonstrated on a record distance of 920 km and even 1840 km on a dedicated fibre network [27,32]. The outcome of such a technique leads to high resolution comparisons between remote clocks in conjunction with the use of femtosecond frequency combs [26,[33][34][35][36][37].…”

“…The high sensitivity detection of the optical phase using heterodyne methods in conjunction with spectrally very pure lasers, are the basic tools to achieve low-noise optical frequency transfer. In the last decade, several experiments in Europe, USA and Japan have explored the limits of this method, paving the way for a new generation of ultra-stable optical networks [18,[21][22][23][24][25][26][27][28][29][30][31]. A groundbreaking frequency transfer has been demonstrated on a record distance of 920 km and even 1840 km on a dedicated fibre network [27,32].…”