Patent ID: 11860008
Assignee: NANJING UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 4:
5. A method of using the self-heterodyne φ-OTDR system with the free multi-spatial resolution according to claim 1, wherein the method comprises:
S1. driving the narrow linewidth laser source to output a continuous laser signal with a high coherence characteristic at a constant power and injecting the continuous laser signal into a subsequent fiber through the isolator;
S2. dividing the continuous laser signal into the three paths of optical signals with equal powers by using the 1×3 fiber-optic coupler;
S3. driving the driver module to synchronously control the three AOMs by using the pulse signal generator to modulate the three paths of optical signals into three paths of pulse light with different frequency shifts;
S4. enabling the three paths of pulse light to pass through the time-delay fibers with different lengths to introduce different pulse intervals, then coupling the three paths of pulse light into the EDFA through the 3×1 fiber-optic coupler for amplification to obtain amplified and coupled optical signals, and injecting the amplified and coupled optical signals into the to-be-detected fiber through the circulator;
S5. inducing a part of the amplified and coupled optical signals comprising vibration information through the circulator, converting the part of the amplified and coupled optical signals into a corresponding electrical signal by using the photodetector, and dividing the corresponding electrical signal into three paths of electrical signals through the electrical amplifier;
S6. performing a filtering processing on the three paths of the electrical signals by using bandwidth filters with different center frequencies, and filtering out a noise signal and a high-frequency signal from the three paths of the electrical signals to obtain three paths of intermediate frequency signals with different frequencies; and
S7. sampling the three paths of intermediate frequency signals by using the data acquisition card to obtain original signals, and adjusting the pulse signal generator based on the original signals, wherein the pulse signal generator and the data acquisition card work synchronously.