Introduction of Distributed Acoustic Wave Sensing System DAS
1. Distributed Acoustic Sensing (DAS) technology:
Use the phase of coherent Rayleigh scattered light instead of light intensity to detect signals such as sound or vibration in the audio range. Not only can the phase amplitude be used to provide information on the intensity of sound or vibration events, but also linear quantitative measurements can be used to achieve the Acquire phase and frequency information of sound or vibration events.
DAS can be considered as a mobile interferometric acoustic wave sensor that detects external signals on the sensing fiber. When sound or vibration causes a linear change in the interfering light phase at the position, the external physical quantity can be realized by extracting the interference signals at different times at the position and demodulating them. Quantitative measurement.
2. DAS measurement principle
DAS measurement process: The laser sends out light pulses along the fiber. Some light interferes with the incident light in the pulse in the form of backscatter. After the interference light is reflected back, the backscattered interference light returns to the signal processing device, and the fiber Vibration and sound waves along the line bring signal processing devices. Since the speed of light remains constant, the measurement result of the acoustic vibration per meter of fiber can be obtained.
3. Introduction to DAS technology
It can detect 40kHZ sound wave signals at most. It can detect
real-time sound wave signals around the fiber at any position (up to 40kHZ). It is
resistant to harsh environments such as high temperature and high pressure, and has
small electromagnetic interference resistance and strong networking capabilities.
4. DAS basic performance indicators:
sensing distance 0-50km
spatial sampling resolution 1m
frequency response range <40kHz
noise level 10-3rad/√Hz
real-time data volume 100MB/sec
Fast response time, typically 1 second
Optical fiber type Ordinary single-mode optical fiber
Measuring channels 1, 2, 4 channels (real-time performance is affected.
Data storage capacity 16TB solid state drive array