Based on the three-layer and double-layer optical fiber waveguide theory,the relation between the fundamental mode resonant wavelength of Gaussian-apodized FBG with different etching depths and the surrounding refractive index(SRI) is numerically analyzed,and experiments are carried out for the response characteristics of fundamental mode resonant wavelength,3 dB bandwidth,and reflection-peak intensity to the SRI.The experimental results show that,as the SRI increases,the movement of resonant wavelength to ...