Observations concerning the reply to our comments on "Fiber optic ultrasonic sensor using Raman-Nath light diffraction"

Kwiek et al. comment further on the reply by Wu et al. (ibid. p. 956-7), stating that Wu et al. acknowledge that their theoretical model is not applicable. The effect of the ultrasound on the light beam ranges from light deflection, via the Raman-Nath regime, to the transition regime approaching Bragg diffraction for the frequency range of 3-15 MHz and under the experimental conditions indicated by the authors. There is no question that optically detectable signals are received; however, they cannot be described by the theoretical model cited by the authors.