Julie, Roufurd. Gain Stability, Phase Stability And Dynamic Range Measurements Of Analogue Optical Links Used For Radio Astronomy. MSc Dissertation. Department of Electrical Engineering, University of Cape Town, 2010.
This dissertation investigates the gain and phase stability and dynamic range of an RFover-fibre optical link as used in a radio telescope. It attempts, via practical experiments, to quantify the gain and phase stability with temperature of the optical fibre and the optical transmitter and receiver. A thermalmodel based on the KAT-7 environment is then defined and together with the stability coefficients determined, the model is used to qualify the link against the KAT-7 requirements. Measurements of gain and phase stability with temperature (at sunset) and movement of the dish are also performed on the XDM dish (a precursor to the KAT-7) to give an indication of the magnitude of gain and phase change in a real optical fibre link installation. Finally an optical transmitter and receiver set is demonstrated to meet the KAT-7 requirement of dynamic range.
To this end: the KAT-7 requirements for gain and phase stability and dynamic range are motivated and discussed, part of which is apportioned to the optical fibre link; software is developed to to control the VNA (the primary measuring device) and log data and controlled experiments using a thermal chamber and a iButton temperature logger are utilised in the data gathering process.
The results are positive in that an analogue optical fibre link will meet the KAT-7 requirements for gain and phase stability and dynamic range.