GPS-over-fiber architecture with relative cable delay monitoring for high precision GPS applications

We propose a novel multi-antenna to one receiver GPSover-fiber architecture with real-time relative hardware delay monitoring. The purpose of this architecture is to perform receiver single difference observation processing without having to deal with a relative receiver clock error parameter and thus to achieve millimetric vertical precision for short baselines. Indeed, past simulations have already shown that a 2 to 3 factor improvement in vertical precision is expected if relative receiver clock error is eliminated in single difference processing and if the relative receiver hardware delay is monitored at millimeter-level precision. 622 22nd International Meeting of the Satellite Division of The Institute of Navigation, Savannah, GA, September 22-25, 2009 In this paper, the proposed GPS-over-fiber setup is first presented and explained. Then, the results of the experiments to test the GPS-over-fiber performance and the relative delay monitoring system are presented. Finally, the calibration procedure and GPS observation processing methodology are described. Results show that with proper oscillators’ synchronization in the RF front-end, signal-to-noise degradation by the opto-electrical circuit can be kept below 2 dB with no significant effect on positioning accuracy. At the same time, the proposed relative delay monitoring system can track the relative delay variations at millimeter-level. The complete system is still under development.