The invention of optical fiber has a history of nearly a century. The early stages of optical fiber had great losses, which limited its application. In the 1960s, under the promotion of Gao Kun and others, Corning Corporation in the United States first manufactured optical fibers with losses as low as 20 dB/km, making long-distance optical signal transmission possible, promoting the practicality of optical fiber communication and the development of related industries. The development of optical fiber communication also greatly promoted the development of software and hardware, including various optical devices and demodulation algorithms. On this basis, it was found that using changes in optical signals can be used to detect various physical parameters (such as temperature, magnetic field, angular velocity, etc.). Common optical signal characteristics include light intensity, frequency, phase, polarization state, etc. Compared with other types of sensors, optical fiber sensors have a series of advantages. Advantages, including size, weight, tolerance to harsh environments, etc, Therefore, it has been widely applied and has become a huge emerging industry.
The distributed fiber optic vibration sensing system (DVS) is based on the optical time-domain reflection (OTDR) technology with phase information, using G652 single-mode fiber as the sensing medium. The laser emits a narrow linewidth pulse laser that is transmitted along the sensing fiber, while continuously generating backward Rayleigh scattered light, which undergoes multi beam interference. When the sensing fiber is subjected to external vibration interference, the phase of the backscattered Rayleigh light will change, causing a change in the intensity distribution of multi beam interference. The photoelectric conversion device detects changes in the intensity distribution of these interference lights and demodulates them into vibration signals. This is why DVS can detect external vibrations.
Characteristics of distributed fiber optic DVS vibration monitoring system:
The monitoring distance of a single host can reach 20-40 kilometers;
Positioning accuracy up to ± 10 meters;
Can distinguish non-human invasion situations such as wind and rain, and reduce false alarms;
Polarization control module ensures precise and stable operation of the system;
Intelligent analysis module filters out false alarms;
No power supply is required in the defense area;
The entire defense zone is passive, explosion-proof, resistant to lightning strikes, electromagnetic interference, does not produce sparks, and has a long service life;
Fiber optic is inherently safe and can be used in high-risk environments;
Support multi machine parallel connection and expand monitoring range;
Multiple alarm methods and remote maintenance management;
Can be used in conjunction with electronic maps for precise positioning;
The system is easy to construct and has low maintenance costs;