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

A second phase-conjugation experiment was conducted in the Mediterranean Se a in May 1997 extending the results of the earlier time-reversal mirror exp eriment [Kuperman et al., J. Acoust. Sec. Am. 103, 25-40 (1998)]. New resul ts 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 r anges other than that of the probe source [Song et al., J. Acoust. Sec. Am. 103, 3234-3240 (1998)], and (3) demonstrating that probe-source pulses up to 1 week old can be refocused successfully. (C) 1999 Acoustical Society of America. [S0001-4966(99)02603-X].