DSTO and TMS Collaborate on New Towed Array System
The Australian Defence Science and Technology Organisation (DSTO) and Thomson Marconi Sonar (TMS) are to develop an advanced fibre optic towed array system demonstrator using embedded fibre optic hydrophones, developed by DSTO, in towed array structures developed by TMS. The end project is expected to have defence and civil applications, the latter in the expanding geophysical survey market.
The hydrophones use a technology in which light is split into two optical paths and recombined to form an interferometer. Sound pressure strains the fibre and this is converted into an electrical signal by demodulation electronics. The technology is similar to fibre optic gyroscopes used in aircraft.
TMS will contribute a high level of experience in linear array design and integration to the project. There have been several attempts to integrate fibre optic transducers within towed arrays in the past but no one has overcome the reliability problems. Conventional towed array acoustic systems use ceramic transducers coupled with preamplifiers, analogue to digital converters, multiplexers and, in some cases, electro-optical converters. These are all embedded in the towed array.
The new fibre optic towed array is expected to be the forerunner of long seismic linear arrays that will require very few internal electronic components. The hydrophones will be linked to a vessel and on-board data processing equipment by optical fibre. This should bring major benefits in terms of increased sensitivity, dynamic range, reliability, maintenance and weight reduction, all resulting in reduced operating times of survey vessels. The demonstrator will include fibre optic transducers as well as conventional ceramic transducers in order to compare the results of both technologies. The validation of the demonstrator is to be performed during several days in an open water tow testing facility.
There is expected to be strong commercial prospects for the final product with analysis of the geophysical survey market suggesting increasing interest in this area, which is currently dominated by a few players world wide. As the fixed and running costs of geophysical survey vessels are very high, companies are increasingly interested in innovations that will maximise operating times of vessels.
With its fibre optic streamer, TMS plans to attract new customers by providing technology which is easier to maintain and more reliable. The ability of the fibre optic to carry a number of multiplexed signals in the same fibre and the small size and weight of the fibre optic will mean that smaller buoyant arrays can be used leading to space and weight reduction when stored onboard a vessel.
Direct benefits are also expected to accrue to Australian industry, in terms of export sales and the development of engineering skills. Once proven in the seismic domain, it is expected that the technology will be translated into new generation military arrays.
-ends-
DSTO and TMS Collaborate on New Towed Array System
