A long-range and variable focus phase-conjugation experiment in shallow water

A second phase-conjugation experiment was conducted in the Mediterranean Sea in May 1997 extending the results of the earlier time-reversal mirror experiment @Kuperman et al., J. Acoust. Soc. Am. 103, 25–40 ~1998!#. New results reported here include ~1! extending the range of focus from the earlier result of 6 km out to 30 km, ~2! verifying a new technique to refocus at ranges other than that of the probe source @Song et al., J. Acoust. Soc. Am. 103, 3234–3240 ~1998!#, and ~3! demonstrating that probe-source pulses up to 1 week old can be refocused successfully. © 1999 Acoustical Society of America. @S0001-4966~99!02603-X#