ABSTRACT

With the advent of increasingly sophisticated sensor technologies, e g digital camera systems coupled to rampant PC processing power, it is d5cult to realise the potential advantages of these technologies, Given the constraints of present ROV electronic architecture ms paper presents some of the latest, essentially digital, developments and suggests how a useful basis for enhanced ROV sensor performance could be extracted.

INTRODUCTION

For many years now, sensor suppliers to the ROV industry have avoided moving to wholly digital transmission technologies Apart from the straightforward use of send digital control and relatively low speed signal h k s, we have been able to rely upon competent analogue signal techniques for many instruments, including video where the cleverly encoded analogue PAL I SECAM INTSC standards have prevailed. Why should this change?

First of all we have the emergence of very high measurement capacity underwater sensors e g digital cameras, high-end imaging sonars, and multibeam echo-sounders, all of which necessarily use intensive digital processing and produce high output data-rates ROVs equipped with these sensors WLU offer new levels of mission capability, particularly in more remote deep water scenarios Constraining such digital sensor outputs into existing transmission channel formats is simply throwing away expensively acquired data

Secondly, we are already using the fibre optic transmission medium which offers almost unlimited capacity for digital signals This fibre technology is being relentlessly progressed by the international telecommunications, videoconferencing and broadcast industries Advances in transmission bitrates are very rapid

Thirdly, in the video field at least, we have the spectacular example set by the broadcast community in its adoption (finally) of a Digital Video Broadcasting standard This has been a long time coming, but has been practically enabled for mass consumerism by the arrival of economic, highly integrated computer chipsets The broadcast community now has the vehicle it needs for massive universal transmission, and interchange not only of programmes, but of material with other rapidly expanding media e g Internet, Telecomms, Videoconferencing, etc

WHERE ARE WE NOW?
Fibre Optic Transmission

New ROV design is already making good use of fibre optic transmission and control signal technology The established advantages of channel capacity, noise immunity and, of course, benefit to umbilical size are reasonably well understood Like most remote systems, operating necessary in cult environments, there is great pressure on designers to increase both data acquisition and control capacities The advent of multiple, high data rate, digital ROV sensors increases this pressure Fibre optic transmission systems have been promoted for some tune now as the panacea for such scenarios, but in the ROV world certain new technologies have to be wholly embraced m order to allow the full real-time potential of fibre optic systems to be brought to bear on the problem

Some basic performance parameters for typical fibres are shown in Table 1 below

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