The invention discloses a polarization-induced
fading resisting method and an alarming
algorithm for
optical fiber bragg
grating sensing signals. Firstly, interference signals reflected back by two adjacent
fiber bragg gratings are received by using a tri-state
polarization diversity receiver, and interference signals having an uncertain polarization state are divided into three paths and then aremodulated by a
signal generator of a
system to form three groups of phase-shifted
light intensity signals of each path; then, the three groups of phase-shifted
light intensity signals of each path are compared with each other in a sampling time period to solve the interference contrast of the three paths of phase-shifted
light intensity signals, the path with the best contrast in the three pathsof phase-shifted light intensity signals is determined, and then the phase
demodulation of the vibration of an
optical fiber sensor is performed by combining a three-step phase shift
algorithm; and then a discrete difference
algorithm is used to process a phase
signal sequence and set an alarm threshold value, and whether an alarm is sent or not is judged by counting the number of discrete difference signals exceeding the threshold value after the difference. The method for determining the contrast of the interference signals has high real-time performance and high accuracy; and the alarming algorithm has high dynamic
signal change monitoring capability, high precision and high environmental
interference resistance.