Radio Interferometer Using Fiber-Optic Links Modulated in the Radio-Frequency Range


IEICE TRANSACTIONS on Electronics   Vol.E82-C   No.1   pp.141-146
Publication Date: 1999/01/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Opto-Electronics
radio interferometer,  geodesy,  delay calibration,  optical link,  

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We investigated a radio interferometer for geodetic use that incorporates commercially available fiber-optic links modulated in the radio-frequency range, and a method for compensating for the delay occurring in the links. With this type of radio interferometer, we can perform baseline analysis without the need for estimating the clock difference between observation stations, which causes a relatively large error in the vertical component of the estimated position of the station. Another advantage of the interferometer is utilization of phase delay, which improves the accuracy of delay determination considerably. By analyzing the interferometer's signal-to-noise ratio, we estimated the practicable cable length to be 58.0 km. The results of preliminary experiments with short optical fiber links show that the differences in the cable delays of the fiber-optic links can be compensated for by calibration signals which make a round trip between the analysis station and the observation sites, and that phase delay can be measured successfully.