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Title: Transatlantic Communications Cable Doubles As Ocean Sensor

Link: https://tech.slashdot.org/story/25/07/16/2246...

alternative_right shares a report from Phys.org: Monitoring changes in water
temperature and pressure at the seafloor can improve understanding of ocean
circulation, climate, and natural hazards such as tsunamis. In recent years,
scientists have begun gathering submarine measurements via an existing
infrastructure network that spans millions of kilometers around the planet:
the undersea fiber-optic telecommunications cables that provide us with
amenities like Internet and phone service. Without interfering with their
original purpose, the cables can be used as sensors to measure small
variations in the light signals that run through them so that scientists can
learn more about the sea. Meichen Liu and colleagues recently developed a new
instrument, consisting of a receiver and a microwave intensity modulator
placed at a shore station, that facilitates the approach. Their work is
published in Geophysical Research Letters. Transcontinental fiber-optic
cables are divided into subsections by repeaters, instruments positioned
every 50 to 100 kilometers that boost information-carrying light signals so
that they remain strong on the journey to their destination. At each
repeater, an instrument called a fiber Bragg grating reflects a small amount
of light back to the previous repeater to monitor the integrity of the cable.
By observing and timing these reflections, the new instrument measures the
changes in the time it takes for the light to travel between repeaters. These
changes convey information about how the surrounding water changes the shape
of the cable, and the researchers used that information to infer properties
such as daily and weekly water temperature and tide patterns.

Read more of this story at Slashdot.

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