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Proceedings Paper

Measuring sub-picosecond optical propagation delay changes on optical fibre using photonics and radio frequency components
Author(s): Roufurd P. M. Julie; Thomas Abbott
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Paper Abstract

To synchronise the elements of a radio interferometer array, a phase stable reference frequency from a central clock is disseminated to the different elements of array. The reference frequency is modulated onto an optical carrier and transported over optical fibre over a distance of up to 12 km. For radio interferometric efficiency, the propagation delay of the transferred reference frequency is required to be stable to less than 3 picoseconds (ps) over 20 minutes. To enable this, the optical fibre transmission line is thermally shielded to minimise length changes due to thermal expansion and contraction on the optical fibre. A test setup and procedure, that measures propagation delay changes to the required accuracy and precision, is required to verify the efficiency of the thermal shielding on the installed optical fibre. This paper describes a method using photonic and radio frequency (RF) components together with an RF vector network analyser (VNA) and post-processing to measure changes in propagation delay on the optical fibre link to sub-picosecond levels. The measurement system has been tested to a stability of < 200 femtoseconds (fs) and a resolution of < 10 fs.

Paper Details

Date Published: 3 February 2017
PDF: 9 pages
Proc. SPIE 10036, Fourth Conference on Sensors, MEMS, and Electro-Optic Systems, 1003614 (3 February 2017); doi: 10.1117/12.2245747
Show Author Affiliations
Roufurd P. M. Julie, SKA South Africa (South Africa)
Thomas Abbott, SKA South Africa (South Africa)

Published in SPIE Proceedings Vol. 10036:
Fourth Conference on Sensors, MEMS, and Electro-Optic Systems
Monuko du Plessis, Editor(s)

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