Product Overview

The distributed acoustic sensing (pDAS) system is a distributed optical fiber sensor based on coherent Rayleigh scattering. It utilizes the sensitivity of optical fibers to sound (vibration). When external vibrations act on the sensing fiber, the refractive index and length of the fiber undergo slight changes due to the photoelastic effect, resulting in simultaneous variations in the optical intensity and phase of the transmitted signal within the fiber.

The phase change caused by sound waves is very small. Therefore, the pDAS system typically uses a highly coherent pulsed light source. Within the pulse width region, interference occurs between the Rayleigh scattering signals. When external vibrations cause a phase change, the intensity of the coherent Rayleigh scattering signal at that point changes. By detecting the intensity variation (differential signal) of the Rayleigh scattering light signal before and after the vibration, vibration events can be detected and accurately located. The principle is shown in the diagram below. Compared to Mach-Zehnder and Sagnac interferometers, the pDAS system requires only a single-core single-mode fiber. It can achieve a maximum measurement distance of 60 kilometers with positioning accuracy within ±1 meter. Furthermore, it can simultaneously detect and locate multiple events.

Product Details:

Advantages of the BLY-pDAS-100P system over other traditional technologies:

Strong resistance to interference: It is not affected by electromagnetic or various light interferences, ensuring good concealment.

The sensing system is distributed, with every 1 meter of optical fiber acting as a vibration sensor.

The system uses a sensing fiber cable as the front-end detector, which neither emits nor receives the following signals:

① Electromagnetic signals

② Radar signals

③ Bidirectional radio signals

④ High-voltage static or transmission signals.

The system is unaffected by metals, saltwater, or minerals in the soil when using a sensing fiber cable as the front-end detector.

The system is immune to ground interference when using a sensing fiber cable as the front-end detector.

The system has strong corrosion resistance when using a sensing fiber cable as the front-end detector.

The outdoor part of the system is passively designed, ensuring intrinsic safety.

The optical sensing signal propagates at the speed of light with a response time of less than 1 second.

It offers long monitoring distances, with a single system capable of monitoring up to 60 kilometers.

Easy operation: It provides a graphical user interface that is easy to understand and operate.

The system integrates seamlessly with third-party software.

The system has built-in interfaces such as network signal output modules, relay output modules, RS232 output modules, etc., allowing for various alarm outputs, including one-to-one, one-to-many, and many-to-one connections with industrial video surveillance front-end and zone alarm outputs.

Basic Information:

The pDAS system, based on coherent Rayleigh scattering, is a distributed sound vibration sensing system that utilizes the sensitivity of optical fiber to sound (vibration). When external vibrations act on the sensing fiber, the refractive index and length of the fiber undergo slight changes due to the photoelastic effect, resulting in simultaneous changes in the optical power and phase of the transmitted signal within the fiber.

The BLY-pDAS-100P model of the pDAS system requires only a single-mode fiber and can achieve a maximum measurement distance of 60 kilometers with a positioning accuracy of within ±1 meter. It can convert every 1 meter of fiber into a fiber microphone sensor, capable of capturing and demodulating sound vibrations at any position along the fiber. It offers a frequency accuracy of 1 Hz and a maximum measurement frequency of 200 kHz. Due to its powerful positioning and sound reconstruction capabilities, it can be integrated with video cameras. The video camera acts as the "eyes" while the BLY-pDAS-100P fiber sound vibration sensing system serves as the "ears." By using both "eyes" and "ears" simultaneously, the accuracy of security assessments is significantly enhanced.

The pDAS system has been widely applied in various fields such as oil well monitoring, defense line security, protection of gas pipelines against excavation, and communication and power line protection. It has proven to be a valuable tool in these areas.

Product Applications:

Widely used in various fields including oil well monitoring, defense line security, prevention of excavations in gas pipelines, and protection of communication and power lines.