Non-destructive testing of composite materials is a key technology issue in equipment testing. Among the emerging new
testing methods, Lamb-wave technology is getting more and more attention. This paper proposed a sensing method to
acquire the Lamb-wave signal in thin plate based on optical low-coherence principles. Methods to acquire Lamb-wave in
thin plate using optical low-coherence technology were analyzed, and the technical path of non-contact, high-precision
method was chosen. Complete in-line experimental system and methods were designed and built up for testing. A sensor
system based on Michelson low-coherence interferometer was set up. The distributed optical fiber sensors were arranged
on the top of sample materials for signal detection. Mirrors to enhance reflection intensity were attached on the sample.
The phase of sensing arm was modulated by PZT vibration. Then signals were detected and processed by Daubechies10
wavelet and Gabor wavelet. In-line testing of thin plate with features of high-precision and high signal-noise-ratio was
realized, which is meaningful to dynamic testing of large-scale structure.