[ISN] Hiding in the noise and chaos

From: InfoSec News (isnat_private)
Date: Tue Aug 20 2002 - 05:38:15 PDT

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    [Raw press releases are rare for ISN, unless its something really 
    interesting, like this one.  - WK]
    Public release date: 12-Aug-2002
    Contact: Gail S. Cleere
    Office of Naval Research 
    Communicating with light polarization
    A new and novel way of communicating over fiber optics is being
    developed by physicists supported by the Office of Naval Research.  
    Rather than using the amplitude and frequency of electromagnetic
    waves, they're using the polarization of the wave to carry the signal.  
    Such a method offers a novel and elegant method of secure
    communication over fiber optic lines.
    Electromagnetic waves, like light and radio waves, have amplitude
    (wave height), frequency (how often the wave crests each second), and
    polarization (the plane in which the wave moves). Changes in amplitude
    and frequency have long been used to carry information (AM radio uses
    changes in the amplitude of radio waves; FM radio uses changes in
    their frequency), but polarization has not been so thoroughly
    ONR-supported physicists Gregory VanWiggeren (Georgia Tech) and
    Rajarshi Roy (University of Maryland) have demonstrated an ingenious
    method to communicate through fiber optics by using dynamically
    fluctuating states of light polarization. Unlike previous methods, the
    state of the light's polarization is not directly used to encode data.  
    Instead the message (encoded as binary data of the sort used by
    digital systems) modulates a special kind of laser light. Van Wiggeren
    and Roy used an erbium-doped fiber ring laser. The erbium amplifies
    the optical signal, and the ring laser transmits the message. In a
    ring laser the coherent laser light moves in a ring-shaped path, but
    the light can also be split from the ring to be transmitted through a
    fiber optic cable.
    The nonlinearities of the optic fiber produce dynamical chaotic
    variations in the polarization, and the signal is input as a
    modulation of this naturally occurring chaos. The signal can be kept
    small relative to the background light amplitude. The light beam is
    then split, with part of it going through a communications channel to
    a receiver. The receiver breaks the transmitted signal into two parts.  
    One of these is delayed by about 239 nanoseconds, the time it takes
    the signal to circulate once around the ring laser. The light received
    directly is compared, by measuring polarizations, to the time delayed
    light. Then the chaotic variations are subtracted, which leaves only
    the signal behind. Variations in stress and temperature on the
    communications would be equally subtracted out.
    "This is quite a clever method, which hides the signal in noise," says
    ONR science officer Mike Shlesinger, who oversees the research. "It
    provides a definite advantage over direct encoding of polarization,
    leaving an eavesdropper only chaotic static, and no means to extract
    the signal."
    For more information on the technology, or to interview Mike
    Shlesinger and his researchers, please contact John Petrik or Gail
    Cleere at 703-696-5031, or email petrikjat_private or
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