### ASA 126th Meeting Denver 1993 October 4-8

## 5aPA2. Pulse-splitting in a nonlinear waveguide.

**Andres Larraza
William F. Coleman
Anthony A. Atchley
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*Phys. Dept., Code PH/La, Naval Postgraduate School, Monterey, CA 93943
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A nonlinear effect in an acoustic duct is described for waveguide modes
above the first cutoff frequency, whereby a finite extent modulation of the
nonlinear mode splits into two disturbances moving with two different
velocities of propagation. That is, for each bit of information input, there
will be two bits output. The effect was first predicted by Whitham for
nonlinear dispersive media [G. B. Whitham, Linear and Nonlinear Waves
(Wiley--Interscience, New York, 1974)]. An experiment to verify this phenomenon
will be discussed. The apparatus consists of a 21-m-long, 7-segment,
thick-walled aluminum tube with a 2-in. internal diameter. Two high-intensity
compression drivers arranged in a push--pull configuration are mounted at one
end to drive a mode above the first cutoff frequency. A 3-m anechoic
termination spanned the length of the last segment at the other end. A physical
explanation of the effect, a simplified perturbative treatment of the problem,
and possible applications to fiber optic communications will be presented.
[Work supported by ONR and NPS Direct-Funding Program.]