Abstract

 
 
 The MeerKAT telescope is a precursor to the Square Kilometre Array, which will rely on optical fibres to link the telescope receivers to a central processor point. The main aspects to consider for the fibre transport are astronomical data transmission as well as timing, monitoring and control. The astronomical data streams from individual dishes to a central building, while the clock signal is distributed from a central point to remote dishes in the telescope array. The MeerKAT telescope, for instance, demands highly accurate and stable clock distribution over up to 12 km of optical fibre to remote dishes. The clock distribution is required for digitisation of astronomical signals. Phase stability is thus critical both for short-term and long-term requirements. In this work, we focused on the short-term stability. Phase noise measurements were performed on optical transmitters used to distribute the clock signals so as to ascertain their contribution to the overall clock jitter of the system. A maximum jitter requirement of 130 fs for a 1.712-GHz clock signal for MeerKAT time and reference is achieved using a distributed feedback laser. We found that with optimised modulation depth, additional passive optical components in the link do not significantly degrade the phase noise response. A distributed feedback laser was proven to be a suitable optical source that will meet the performance and link budget requirements for the MeerKAT telescope.
 
 
 
 
 Significance: 
 
 
 
 A distributed feedback laser is recommended for the design of the MeerKAT time and reference system as it is a suitable optical source that will meet the performance and link budget requirements.
 
 
 
Highlights
In the quest to explore our universe, human curiosity has led to the conception of the Square Kilometre Array (SKA)
The SKA is derived from the total receiver collecting surface area of all receiver components which will amount to one square kilometre
This study focused on optical transmitters as one of the components contributing to the overall degradation of the phase noise performance in an optical fibre link
Summary
In the quest to explore our universe, human curiosity has led to the conception of the Square Kilometre Array (SKA). A clock signal will be required for generation of a stable reference tone for phase coherence of the dishes; absolute time code for antennae controllers and beam formers; accurate timing ticks and counters for data stamping; operational monitoring and control; stable periodic synchronisation; and running the digitisers.[2] The use of optical fibres in clock distribution has been previously reported.[3,4] Existing telescopes have used optical fibre links for timing and frequency reference distribution. A 25.3-km ITU-T G.655 fibre and 1x4 splitter were in cluded in the link and the jitter value was obtained
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