Page 59: of Offshore Engineer Magazine (Apr/May 2014)

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Standards Differentiating subsea

Subsea

Subsea wireless video wireless technologies

SWIG is developing a set of standards to transmission.

There are currently three types of subsea support interoperability between acous-

Image from WFS wireless communication technologies: tic, radio and optical systems subsea.

Technologies acoustic, radio, and free-space optics (FSO). Work began on this body of standards lower bandwidths than in 2012, focusing initially on radio. The Each can be used on their own, and optical systems.” draft subsea radio standard was peer together, for subsea wireless communi-

Acoustic signals, or reviewed last year, then presented to cation. Performance factors to be taken sound waves, travel the American Petroleum Institute (API) into consideration for deployment are: more slowly through Subcommittee on Subsea Production bandwidth, range, ef? ciency, cost, and water than electro- Equipment (SC17) in January. No deci- reliability. magnetic (RF and sion has been taken yet as to which sub- Each have their own bene? ts. Acoustic optic) waves (although committee it will come under. This will through-water communication, for exam- sounds travels faster be discussed at an API meeting in June. ple, offers a long-range solution, but is through water than air), “Radio was chosen ? rst because it was limited in the data it can transmit, while but, because the wave the easiest standard to develop given the optical communications can transmit HD lengths are longer, and number of radio standards available for video over a 1-500m range, but its signal frequency shorter, they industrial applications,” Crowther says. is susceptible to turbidity, bio-fouling travel further and are “The idea is it would also create a tem- and light interference.

more robust, but have plate for the others, with future standards Here we give and introduction to each, a lower bandwidth, so referencing the ? rst. Work has begun on with help from SWIG and its members.

carry less data. acoustics and free-space optics standards.

Acoustics

Wireless signaling Work will begin on subsea inductive works by encoding, or power transfer in mid-2014. Acoustic subsea communication is the 21st century subsea comms modulating, a sound These standards will be brought most established through-water wire- or EM wave by altering its shape in a together to form a single hybrid technol- less communication technology in the operators want answered; “how fast and way related to the data required to be ogy standard, to provide a platform on offshore oil and gas sector. how far can it communicate,” says Ian communicated. which all the technologies can work It has been used in the industry for

Crowther, a director at Edinburgh-based Over time, methods have been devel- together on certain levels.” more than 40 years, but it has only

WFS Technologies. “It is dependent on oped to create more complex signals, or The initial work on the acoustics stan- recently been honed to a level at which many things, not least if a particular wave-shapes, by modulating the ampli- dard has focused on investigating how to operators are con? dent to use it for system can work in a particular operating tude, frequency or phase of the signal de? ne an open standard in a relatively primary control on critical applications, environment. either in analogue or digital data format. mature market with several de facto stan- such as primary control of subsea well “Optical systems can carry very high But, the transmission methods for acous- dards developed by competitors, most of isolation devices. bandwidth and, provided the water tic and EM signals differ. whom are members of SWIG. Acoustic signaling uses pressure is clear, transmit over relatively long (sound) waves in water. Their lower fre- distances,” Crowther says. “Radio is less quency means less data can be transmit-

Subsea wireless technologies quick reference sensitive to the environment, communi- ted than a radio or optical signal; but it

MeterAcoustic RF Optical cating through high levels of turbidity, can be transmitted signi? cantly further

BandwidthText messageStreaming videoHD video inside complex structure and through because water attenuates pressure waves

Maximum range100-10,000m1-100m 1-500m solid barriers including the seabed, far less than optical or radio wave forms.

concrete and even metal. But it supports One of the best known uses for under-

Environmental Turbidity Motor interference Light interference limitations Gas bubbles Steel structures Bio fouling water acoustic signaling is position-

Bio fouling Turbidity ing, for vessels or subsea assets, such

E