Broadband serrodyne phase modulation for optical frequency standards and spectral purity transfer.

We perform low phase noise, efficient serrodyne modulation for optical frequency control and spectral purity transfer between two ultrastable lasers. After characterizing serrodyne modulation efficiency and its bandwidth, we estimate the phase noise induced by the modulation setup by developing a novel, to the best of our knowledge, composite self-heterodyne interferometer. Exploiting serrodyne modulation, we phase locked a 698 nm ultrastable laser to a superior ultrastable laser source at 1156 nm by means of a frequency comb as a transfer oscillator.

Optical interferometry-based array of seafloor environmental sensors using a transoceanic submarine cable.

Optical fiber-based sensing technology can drastically improve Earth observations by enabling the use of existing submarine communication cables as seafloor sensors. Previous interferometric and polarization-based techniques demonstrated environmental sensing over cable lengths up to 10,500 kilometers. However, measurements were limited to the integrated changes over the entire length of the cable.

Coherent phase transfer for real-world twin-field quantum key distribution.

Quantum mechanics allows distribution of intrinsically secure encryption keys by optical means. Twin-field quantum key distribution is one of the most promising techniques for its implementation on long-distance fiber networks, but requires stabilizing the optical length of the communication channels between parties. In proof-of-principle experiments based on spooled fibers, this was achieved by interleaving the quantum communication with periodical stabilization frames.

SI-traceable frequency dissemination at 1572.06 nm in a stabilized fiber network with ring topology.

Frequency dissemination in phase-stabilized optical fiber networks for metrological frequency comparisons and precision measurements are promising candidates to overcome the limitations imposed by satellite techniques. However, in an architecture shared with telecommunication data traffic, network constraints restrict the availability of dedicated channels in the commonly-used C-band. Here, we demonstrate the dissemination of an SI-traceable ultrastable optical frequency in the L-band over a 456 km fiber network with ring topology, in which data traffic occupies the full C-band.