Lasers keep submarines in touch through the big blue

 作者:折孬     |      日期:2019-03-14 06:19:03
THE water that hides enemy submarines also makes it hard to contact the friendly ones from the air – unless they surface. Reaching submerged subs has required giant transmitters sending very low-frequency radio waves, which limits data transmission speeds. Now the US Defense Advanced Research Projects Agency is turning to new blue lasers to get the message through. It has long been known that blue light penetrates water well. DARPA tried to develop blue laser links to subs around 1980, but failed as the lasers available were inefficient. DARPA’s fresh shot utilises new compact lasers that emit blue light,