The ALMA photonic local oscillator system

Abstract

The Atacama Large Millimeter Array (ALMA) Photonic Local Oscillator (PLO) is an advanced photonics system that generates and distributes all of the Local Oscillator (LO) and timing references for the ALMA radio telescope array. These LO and timing references are used by the receivers and electronics at the antennas, and by the Correlator in the central building. Due to the unprecedented combination of high sky frequencies (up to 950 GHz) and long baseline lengths of up to 15 kilometers, the ALMA 1^st LO requirement is particularly stringent, with extremely precise timing and synchronization needed down to the ~10 femtosecond level.