David Gozzard

High-precision optical-frequency dissemination on branching optical-fiber networks

We present a technique for the simultaneous dissemination of high-precision optical-frequency signals to multiple independent remote sites on a branching optical-fiber network. The technique corrects optical-fiber length fluctuations at the output of the link, rather than at the input as is conventional. As the transmitted optical signal remains unaltered until it reaches the remote site, it can be transmitted simultaneously to multiple remote sites on an arbitrarily complex branching network. This technique maintains the same servo-loop bandwidth limit as in conventional techniques and is compatible with active telecommunication links.

Square Kilometre Array: The radio telescope of the XXI century

The Square Kilometre Array (SKA) will be the world’s largest and most sensitive radio telescope. It will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of theUniverse, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. This project envisages the construction of 133 15-m antennas in South Africa and 131072 log-periodic antennas in Australia, together with the associated infrastructure in the two desert sites. In addition, the SKA is an exemplar Big Data project, with data rates of over 10 Tbps being transported from the telescope to HPC/HTC facilities.

Stabilized microwave-frequency transfer using optical phase sensing and actuation

We present a stabilized microwave-frequency transfer technique that is based on optical phase sensing and optical phase actuation. This technique shares several attributes with optical-frequency transfer and, therefore, exhibits several advantages over other microwave-frequency transfer techniques. We demonstrated the stabilized transfer of an 8000 MHz microwave-frequency signal over a 166 km metropolitan optical fiber network, achieving a fractional frequency stability of 6.8×10-14  Hz/Hz at 1 s integration and 5.0×10-16  Hz/Hz at 1.6×104  s. This technique is being considered for use on the Square Kilometre Array SKA1-mid radio telescope.