@fibresystemsmag |
www.fibre-systems.com
FEATURE SUBMARINE CABLES
The latest NEC earthquake/tsunami sensor units, commissioned since the 2011 earthquake and Tsunami and now being rolled out
had been installed on NEC’s submarine cables in 10 locations since 1979. ‘Since the 2011 Great East Japan Earthquake, NEC has also deployed new technology to predict the intensity of an earthquake’s secondary big wave and the height of the possible tsunami,’ added Simon Webster, head of submarine networks at NEC Europe. ‘NEC is now building submarine cable networks extending over 5,000km for improved coverage and accuracy.’ Packages of sensors to measure water
temperature, pressure, and conductivity can also be installed with the repeaters deployed every 50-70 km to amplify optical signals in submarine cables. Tat would help scientists better understand climate change, Webster explained. ‘It’s important to ensure that the proximity of the repeaters does not disrupt the data being collected,’ he added. ‘Although a repeater’s power consumption is only a few tens of watts, we’re aiming to detect sea temperature variations measured in milliKelvin, so care must be taken in designing and locating the temperature sensors. Te inclusion of sensors in the same mechanical housing as telecom repeaters may
also cause concerns for cable owners whose principal purpose is to provide reliable telecommunication services, so both physical and functional separation of sensors from critical telecom elements may be required.’ Peter Phibbs of Mallin Consultants in
Vancouver, Canada, underlined that instrument choice also influences the feasibility of dual telecom/sensing usage. ‘Tey have to handle being run across the stern of a cable ship and laid into the ocean,’ he said. ‘Once they’re laid the chances are no-one will ever go and see them again. Cameras or any instruments that have a lifespan of months; it’s doubtful whether they’re worth putting on, and they’ll pull too much power. To not impact reliability, you’re restricted to a repeater-type power supply that’s about 50W.’ By contrast, bandwidth considerations are
comparatively unimportant, explained Phibbs, who managed the deployment of NEPTUNE Canada, is on JTF committees, and has authored several reports on green cables. ‘NEPTUNE requires about 4 Gb/s from each cable, which is nothing. Submarine cables are now typically
In Japan, seismometers had been installed on NEC’s cables since 1979
carrying 100x100-Gb/s waves on each fibre pair. Te data from these instruments will probably be carried in an out-of-band channel, where the ability to transmit at 100 Gb/s drops off, but fairly high speed transmission is still possible.’ Discussions about such issues have gone a long
way to persuading suppliers to offer ‘Green Cables’, Phibbs said. ‘Cameras and active sonar are unfeasible, but you get a lot of benefit out of pressure transducers, accurate temperature, and some measurement of ground shaking. Industry has now said, “We can handle that package without significant impact to the telecom provider”.’
Issue 6 • Winter 2015 FIBRE SYSTEMS 19
NEC
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37