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Communications The Military Technology

Navy Scientists Develop Laser For Underwater Communication 83

Researchers at the Naval Research Laboratory claim to have come up with a better tool for underwater acoustics. The new system uses laser light to create sound underwater from a distance. This technology could allow planes a much easier method of communicating with submarines without the need for a floating buoy. "Efficient conversion of light into sound can be achieved by concentrating the light sufficiently to ionize a small amount of water, which then absorbs laser energy and superheats. The result is a small explosion of steam, which can generate a 220 decibel pulse of sound. Optical properties of water can be manipulated with very intense laser light to act like a focusing lens, allowing nonlinear self-focusing (NSF) to take place. In addition, the slightly different colors of the laser, which travel at different speeds in water due to group velocity dispersion (GVD), can be arranged so that the pulse also compresses in time as it travels through water, further concentrating the light. By using a combination of GVD and NSF, controlled underwater compression of optical pulses can be attained."
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Navy Scientists Develop Laser for Underwater Communication

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  • by myVarNamesAreTooLon ( 1474005 ) on Monday September 07, 2009 @01:40PM (#29342153)
    ...but do they have plans to attach them to sharks?
  • by Anonymous Coward

    I knew it! Sharks With Frickin' Lasers!

    • Yeah, but these sharks with freaking lasers are just tomorrow's generation of kids with their freaking mobiles. In my days, if you wanted to talk, you had to get out of the water. Now get off my lawn.
  • So what's to prevent someone's hydrophones from picking this up and realizing that there's a submarine within audible range of the communication?

    • Re: (Score:3, Interesting)

      by Kamokazi ( 1080091 )
      They would probably have regulations on when this method of communication can be used once (if) it is put into use.
    • Re: (Score:3, Interesting)

      by Vahokif ( 1292866 )
      • by cwebster ( 100824 ) on Monday September 07, 2009 @02:08PM (#29342441)

        The issue isnt eavesdropping, its that the mere act of communicating gives your position away to everyone when wants to know.

        • Giving your position away to everyone when wants to know sometimes feels like it's been a mainstay of the US submarine service since the 60s, If they really give a damn that their subs will be even noisier when everyone else is working on making them as stealthy as possible, they'd probably build a few non-nukes.
        • by selven ( 1556643 )
          Steganography? As for how you would implement it, manufacture thousands of cheap dummy floating communicators and put them in the sea?
        • by worip ( 1463581 )
          220 decibels of sound can travel very far (especially underwater), I bet the submarine can be quite far away and will still be able to pick up the sound signal. IF (and this 'if' is a very handwavey kind of if) the range of this is say more than a few tens of kilometers, it would be hard to find the submarine anyway in a volume that large.
    • Based on the article, being able to generated phased sound at multiple points would be an improvement over the current method of dunking a speaker in the water. This would have the ability to transmit from mulitple points and create a directional sound, in theory pointed away from the enemy and towards the friendly.

    • what is to prevent someone from searching for an exposed buoy like it is now?

    • Re: (Score:3, Insightful)


      Obviously you don't communicate directly with subs during hostilities using methods that can be easily overheard.

      Why do so many slashdotters think that experts have not thought of their brilliant insight many years ago?

      • by mysidia ( 191772 )

        Yep... and there's a great method that cannot be "overheard" in an area, because the transmission can be heard all over the planet. ELF transmissions from the ground.

      • Part of the general Internet phenom, "I just read the headline of an article, and my first thought will be a brilliant insight that people who devote their lives to this subject won't have thought of." Elivated to an art form in left-wing critiques of millitary affairs, and right-wing attacks on evolution and climate science.
    • by mysidia ( 191772 )

      They could randomly generate "dummy" communications in places where there are no submarines much more often and in many more places than there are actually submarines.

      • That's sort of like hiding the rubber ball under an infinite number of cups. The problem is the enemy can track every single cup. Humans are terrible about coming up with truly random patterns so eventually some sort of pattern would show up in the tracking and predictive analysis would start to give the enemy an idea of where to look.

        It would also be expensive in fuel, wear and tear, and the occasional loss of crew and aircraft to keep a pseudo random lasercomms program running. We don't even patrol fo

        • by mysidia ( 191772 )

          How is it that the enemy can track every cup?

          You think they can build a global sensor net and detect every time the laser is used?

          I think it would be enough for computers onboard a plane that has a message to send to periodically activate the laser to send the (timestamped, encrypted) message at random intervals during the flight.

          Enemies in the water that receive the signal will have no idea as to the ultimate destination of the aircraft, only presumably that the sub may have been expected to be (at

    • So what's to prevent someone's hydrophones from picking this up and realizing that there's a submarine within audible range of the communication?

      maybe the fact that it will not be used from the submarine platform. The navy has been investigating the use of blue-green lasers [] for one way comms to submarines for ages, both to improve bandwidth and to reduce the footprint of the signal. I do not see this as a communication tool, in my view it's an high tech Sonar Ping generator. []
      with enough computing power and using part of the bandwidth to signal the precise location of the laser hits, it might turn into a bistatic active sonar, in which the a

    • Re: (Score:3, Informative)

      by ceoyoyo ( 59147 )

      Dropping a sonobuoy and transmitting a message tends to have the same effect.

      There are apparently circumstances when you need to have a chat with a submarine and it's worth giving away that there's a sub somewhere within X km, in some direction. On the other hand, since you don't have to drop a buoy every time, with the laser system you could potentially go around broadcasting some dummy messages too.

      • Also, letting people know that there's a sub somewhere within X km (where x is a fairly large number, the sub could hear a 200+ dB signal for a long way) is less useful than you might think. A circle several kilometers in radius is still a pretty big place to look for a sub, if you even happen to have a platform within range that could do the searching.
    • So it seems this would be a great excuse to put a reasonably high powered laser in space.

      It could communicate with submarines over a vast area (I don't mean by illuminating the entire area at once, instead it would target many different pinpoint locations only one of which has the submarine it wants to communicate with).

      The enemy wouldn't even be able to follow the track of aircraft that would otherwise be communicating with the submarines.

      Instant, high bandwidth communications down to submarines worldwide

    • by b4upoo ( 166390 )

      I'm shocked that the military would talk about this new technology.

    • Given how well water conducts sound (and pressure waves in general), "within audible range" is still pretty fuzzy.

      No, my concern goes more towards the natives. There's already been studies pointing towards our nice underwater technology confusing the hell out of any marine lifeform that uses sonar, so now we're gonna add 220dB blasts to it ?
  • To Swimmers and wildlife, when a plane is shooting this giant high-powered laser into the water, to communicate with the submarine?

    achieved by concentrating the light sufficiently to ionize a small amount of water, which then absorbs laser energy and superheats. The result is a small explosion of steam, which can generate a 220 decibel pulse of sound.

    • by beefnog ( 718146 )
      It would pose a danger if you were in the area. However, submarines aren't usually found in surfer territory and anybody swimming in the North Atlantic is probably glad to see the plane. As for marine life, you can make the sound of a high enough frequency that marine life will be unaware and unaffected. It's not like we'll be using this as a bitchin' megaphone for unencrypted voice.
      • by mysidia ( 191772 )

        I'm thinking more along the lines of swimmers in the North atlantic who are tethered to a boat and on a dive expedition...

        • Re: (Score:3, Informative)

          by John Hasler ( 414242 )

          Swimmers would be in about the same danger of being zapped by this thing as they would of being hit on the head by one of the air-dropped buoys that it would replace.

    • How does this NOT pose a danger To Swimmers and wildlife

      Because the Navy's Selachimorpha [] already ate them all then moved away to a safe distance, that's how.

    • Re: (Score:2, Informative)

      by Mozk ( 844858 )

      Interesting note: it also occurs the other way around with sonoluminescence []. Intense sound through a liquid can create light.

  • It's like an acid trip man. I can like hear the pretty colors. Oh look, I see noise. Dude, this is soooo cool. Want some?

  • by BigSlowTarget ( 325940 ) on Monday September 07, 2009 @01:50PM (#29342265) Journal

    I don't know how the audio volume of this system compares with sonar systems (though the article's 220db and 160db from kind of gives clues and weakly suggest might be as much as 64x), but I suspect the people who oppose the use of sonar by the navy on the theory that it hurts whales are going to go nuts over this one.

    There is no where near enough info to actually assess any kind of threat, but I'm sure the panic button will be hit anyway.

    • Re: (Score:1, Insightful)

      by ibsteve2u ( 1184603 )
      Need a moderation tag for "Informative, yet sadly obvious.".
    • by fluffy99 ( 870997 ) on Monday September 07, 2009 @02:04PM (#29342397)

      Active Sonar output is limited by cavitation. That is the boiling of the water on the surface of the transducer, which acts like a blanket attenuating and distorting the output. In general that means under 200 dB. Still plenty to cause problems with local wildlife. Active sonar is not used very often at its also like turning on a spotlight in a dark room.

    • Re: (Score:3, Interesting)

      by John Hasler ( 414242 )

      The 220 db figure is probably the sound pressure right at the surface of the bubble. That tells you nothing useful as to the hazard to wildlife: depending on the pulse energy and repetition rate the bubbles could be as small as a few microns in diameter and the sound level nearby quite modest. The ability to create large "virtual" phased arrays should also reduce the need for the very high energy pulses used in some current systems.

    • Re: (Score:3, Insightful)

      I hope it does push the panic button. It is one thing for us to defend ourselves. It is quite another for us to make another species miserable or extinct while attempting to optimize a way to defend ourselves from our own fears. Public outcry and discussion can give us pause so that we can investigate whether the effectiveness outweighs the possible ethical costs, and hopefully come up with a thoughtful solution.
      • Re: (Score:3, Interesting)

        by maeka ( 518272 )


        Let's play devil's advocate and assume the Navy is needed and capable of "defending ourselves."
        How many whales are worth one human life? How much whale misery is equal to human misery? What are the ethics of letting humans (of any nation) die in order to save a whale or give said whale a better life?

        I ask this simply because you put it in the context of defense, not (financial) cost.

        This is the one environmental question I don't see asked enough. Choosing the less effective method for environmenta

        • by drerwk ( 695572 ) on Monday September 07, 2009 @07:22PM (#29344957) Homepage
          Get back to me when there are 6 billion whales with and expected increase of 3 billion over the next decade or so. I would be willing to give up a nation of people if I could put the ocean back the way it was a hundred years ago.
          • Re: (Score:2, Insightful)

            by woolpert ( 1442969 )

            Who, exactly, are you willing to kill / let die to achieve your goals.

            • Re: (Score:3, Interesting)

              by drerwk ( 695572 )
              Intro to moral philosophy was not my best class. But a lottery would certainly be fair. Instead I would suggest we outlaw those activities that cause harm, let's not argue about the method of measurement, to the ocean, or specifically whales. And if in fact as some ancestor post suggested this will result in human death, then so be it. You know, it is demonstrable that lowering the speed limit on highways reduces death by collision, but we re perfectly happy to leave the limit high for our convenience. Seem
  • by Anonymous Coward on Monday September 07, 2009 @01:55PM (#29342317)

    I wonder how many marine animals we'll cause to go deaf from this, which would probably end any chance of survival for those affected. 220 decibels is incredibly loud in the air, I can only guess the extended intensity it travel with underwater...

    • Re: (Score:1, Informative)

      by Anonymous Coward
      You are mixing up apples and oranges. The dB level in the water is not directly related to the dB level in the air. As Discovery of Sound in the Sea [] says:

      Confusion arises because relative sound intensities given in dB in water are not directly comparable to relative sound intensities given in dB in air.

      ... The result is that sound waves with the same intensities in water and air when measured in watts per square meter have relative intensities that differ by 61.5 dB. This amount must be subtracted from relative intensities in water referenced to 1 microPascal (ÂPa) to obtain the relative intensities of sound waves in air referenced to 20 microPascals (ÂPa) that have the same absolute intensity in watts per square meter.

    • by moon3 ( 1530265 )
      Dolphins and Orcas already casted their veto, but we will probably see more of their beaching suicide attempts to flash their opinion on the matter in the near future. Maybe those stupid humans would finally get any clue.
  • will this kill flipper?

    • Flipper died years ago, caught a nasty virus.

    • Well, let's just say you might want to consider changing Flipper's name to "Flopper".

    • It's hard to say.

      A laser in water travels at approx 140000 miles per sec. (I'm excluding salt content and impurities).

      Flipper is faster then lightning
      which is upper end 87000 miles per sec.

      Discounting any major currents giving flipper an advantage

      140000 - 87000 = 53000

      So the question is really whether Flipper is 53000 miles per second faster then lightning?

      Answers on a postcard please to

      Pressure Squished Dolphin Sanctuary
      Coral Key Park and Marine Preserve

  • bad acronym (Score:3, Funny)

    by Jeek Elemental ( 976426 ) on Monday September 07, 2009 @02:15PM (#29342507)

    they should call it NSFW (Not Safe For Whales)

  • What, you can do that now? Why didn't anybody TELL me this??!
  • One word (Score:1, Redundant)

    by surfcow ( 169572 )


  • Subsurface Hydro-Acoustic Radiation Communication System (SHARCS)
  • That's my first and only thought, really.
  • Communication my arse! how long before this is turned into a weapon. Or is "communication" some secret word for "Killing" that I havent been told about?

    "Tha' 'll communicate 'em cap'n'"
  • This sounds like it would be useful as a directed energy weapon, especially with the ability to compress waves over a distance.

  • Anyone else misread the title as "Navy Scientists Develop Laser for Underwear Communication"?
  • Potential injury to marine life aside - I'm interested to know how such a system can overcome the extreme variability of seawater. From what I just read this isn't as simple as sonar sending a circular pulse out and getting a 'bounceback'; this is sending information. Surely the abundance of microorganisms, animal matter, let alone local variations in saline and other chemical content which strongly define the physical properties of seawater would be difficult to adjust for?
  • There are animals in the Ocean that make noises as loud as this..

    Take the Pistol Shrimp for example: []

    That makes 200db's just by snapping it's big claw.. (albeit at a much shorter range)

    Interestingly the 'explosion' caused by the snapping reaches temperatures close to that of the suns surface!

1 Mole = 007 Secret Agents