Numerical calculation method is adopted to analyze to the influence of the polymer material on the sensitivity of coated FBG. The calculation results show that, the polymer material with high Young's modulus and high thermal expansion coefficient helps to improve the temperature sensitivity of the coated FBG; and the material with low Young's modulus and low Poisson's ratio helps to improve the pressure sensitivity. The polymer-coated FBG experiment is explored, in which the pressure and temperature sensitivities are enhanced 12-fold and 7-fold respectively.

A new kind of passive underwater acoustic sensor based on fiber Bragg grating is reported. The pressure sensitivity of the sensor is enhanced three orders of magnitude being packaged with polymer material, which is a foundation for underwater acoustic detection. An intensity modulation scheme is adopted to realize high-accuracy detection due to the extra-narrow line-width laser. The experimental results show that the sensor’s noise-limited pressure detection resolution is about 61dB (0dB＝1μPa/ Hz ) at 500 Hz, which satisfies the application of underwater target detection.