Conduction current signalling in the vicinity of a sub-sea offshore structure

This paper reports the results of a series of measurements designed to determine the viability of using conduction current techniques for data transmission in the offshore platform environment. The results show that ranges predicted some authors for conduction current systems in the open were not observed in practice. In particular, measurements conducted in the vicinity of a large metallic underwater structure show an increase in signal strength accompanied by a reduction in bandwidth compared with open sea case. The signalling rates which could be accommodated in the vicinity of an under water structure approximately 75% of the corresponding rates in the open sea. The noise amplitude at each test site was considerable, being composed predominantly of harmonics of land based power frequency. Such noise can be reduced acceptable levels using filtering techniques. For high signal-to-noise ratios a typical signalling rate at a range of 100m in the open sea was found to be 200 baud.