Submarine cable network of use to Sydney scientist.
Scientists have called for telecommunications companies to open up their old and new submarine cables to climate change research.
According to Sydney University scientist John Yuzhu You, undersea cables could be used to monitor currents, salinity, seismology and ocean temperatures.
As water moved around a cable, it generated an electromagnetic current that could be measured by voltmeters at cable landing stations, You explained.
Voltmeters would cost up to $3,000 to set up, he said, and because fibre optic cables could remain under the sea for decades, they could be a consistent, continual source of data for researchers.
“Only a tiny fraction of the existing undersea cabling is used for scientific purposes … this is a missed opportunity,” You said.
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At first I thought this might be silly, since you can’t generate or detect voltage in a glass fiber but then I had a look at this diagram:
1 – Polyethylene
2 – Mylar tape
3 – Stranded steel wires
4 – Aluminium water barrier
5 – Polycarbonate
6 – Copper or aluminium tube
7 – Petroleum jelly
8 – Optical fibers
I assume then he’s talking about putting a voltmeter on either the copper/aluminum jackets.
Interesting idea. Full story here
“As water moved around a cable, it generated an electromagnetic current that could be measured by voltmeters at cable landing stations, You explained.”
It’s the Abbot & Costello sketch again.
gallopingcamel says:
August 15, 2010 at 12:04 am
“With regard to electric induction effects into the basic (copper) coaxial cable, can anyone tell me how this is supposed to work?”
I would assume that the intention would be to inject an AC signal and measure the transmitted and reflected waves as the frequency is ramped up from DC to maybe ~300MHz. They might be thinking of something much cruder, though; put a DC current through the cable, generating a magnetic field; motion of the electrically conductive water through that magnetic field in turn generates a voltage in the cable.
jtom says:
August 14, 2010 at 1:24 pm
“If a sea floor is soft, copper cables might sink a little, or be covered with silt. This doesn’t happen much with fiber cable because it is substantially lighter, and I think that may cause a problem with the proposed research.”
If the fibre cable is armoured as in the diagram, or even just with the copper and aluminium inner portions, then its relative density will be ~4 or 5, more than enough to sink into (some of the) silt, or be covered by it. It would only take a few centimeters of covering to affect the signal markedly, unless we are talking very low frequencies. But with low frequencies (long wavelengths) one would be unable to resolve sections in which the amount of cover varied along the cable length on metre scales. This all seems horrendously messy.
crosspatch says:
August 14, 2010 at 12:24 pm
“and an unwilligness to share IP on anything developed stopped those.”
To measure the sea speed, I think what the scientist wants to do is measure the voltage at both ends of the cable. A bit like the Hall effect: Google wikipedia.
A problem that i see is if the cable is 1000 kms long, you can only get the average current across the entire cable. Also, you have to integrate the sea velocity not just next to the cable, but also at a diminishing vertical distance from the cable.
Another problem / challenge i see is geomagnetic currents are quasi-dc currents that could distort the results.
Another problem comes about from DC transmission lines that may have DC currents leaking within the area of measurement of the copper cable. This is a problem: the earth connection to ground has to be large enough to prevent old magnetic compasses on ships giving false magnetic north south readings due to distorted magnetic fields arising from the DC transmissnio line earth connection for monopolar lines.
Another problem I see is that the earth has currents flowing through the magma, will this also distort the results?
Interesting idea still, maybe simplistic?
Looking for a contact for John You, the promoter of the idea. Sydney University does not have his current contact details. Need to understand the parameters under which his scheme will work.