Title :
Precision timing control for radioastronomy: maintaining femtosecond synchronization in the Atacama Large Millimeter Array
Author :
Cliche, Jean-Francois ; Shillue, B.
Author_Institution :
Teraxion Inc., Sainte-Foy, Que., Canada
Abstract :
This article discusses three important subsystems of the photonic LO reference distribution system for the ALMA radiotelescope. Each subsystem relies on specific control systems that allow ordinary components to be assembled to form a global system that is more accurate and stable than its individual components. By using appropriately designed loops, lasers with phase noise of many thousands of rad2 were phase-locked to generate high-purity microwave signals with phase noise below 3.3 × 10-5 rad2 at 27 GHz, fibers with lengths fluctuating by more than a few millimeters were compensated within a fraction of a micrometer, and optical frequencies of lasers normally fluctuating by tens of megahertz were stabilized to within a few kilohertz. These examples demonstrate how control systems can be used with photonic and electronic systems to achieve remarkable results.
Keywords :
astronomical telescopes; millimetre wave antenna arrays; millimetre wave detectors; optical fibre communication; synchronisation; 27 GHz; Atacama Large Millimeter Array; electronic systems; femtosecond synchronization; high-purity microwave signals; lasers optical frequencies; local oscillator reference distribution system; phase noise; photonic systems; precision timing control; radioastronomy; Control systems; Fiber lasers; Laser noise; Laser stability; Masers; Phase noise; Radio control; Timing; Ultrafast electronics; Ultrafast optics;
Journal_Title :
Control Systems, IEEE
DOI :
10.1109/MCS.2006.1580149