The invention provides an 
optical fiber sensing system. The 
system comprises a 
laser which is used for transmitting 
continuous light of a designated frequency, an acousto-optic modulator which is usedfor receiving the 
continuous light and modulating the 
continuous light into a differential 
delay pulse pair, a 
circulator which is used for receiving the differential 
delay pulse pair and outputtingthe differential 
delay pulse pair to a sensor, the sensor which is used for 
processing the differential delay pulses output by the 
circulator to form a light pulse and sending the light pulse to a 
detector through the 
circulator, the 
detector which is used for receiving the light pulse to form an interference 
light signal, converting the interference 
light signal into an interference electrical 
signal and sending the interference electrical 
signal to an analog-
digital converter, the analog-
digital converter which is used for converting the interference electrical 
signal into an interference 
digital signal and sending the interference 
digital signal to an FPGA module, and the FPGA module which is used for controlling a driver to generate 
radio frequency pulse signals of different frequencies, and carrying out phase 
algorithm processing according to the interference 
digital signal to acquire phase information. According to the invention, the acousto-optic modulator is used, which effectively reduces the cost; and a front-end MZ interferometer is eliminated, which can effectively eliminate the interference of the 
environmental noise.