Based on the principle of fiber-capacitance drop analysis method

salinity detection is studied.The experimental results of 20 kinds of solution with different salinity show that the optical fiber signal value and area under liquid droplets fingerprints diagram curves increases with increase of salinity.Using 1—12—1 three-layer BP neural network structure

and average value of the optical fiber signal and the area under the curve of the liquid droplets fingerprints as input vectors respectively

and BP neural network is trained and uses the trained network to test respectively.It is derived by comparison of test results

salinity detection effect using mean value of optical signal as input vector of the BP networks is better than the others

and the maximum detecting error is 0.14 %.