Optical fiber monitoring system products are complex systems composed of integrated optics, electronics, mechanics and software algorithms, and are the latest generation of optical fiber sensing technology products. The system adopts optical fiber connections without signal loss. Optical fiber works as transmission medium and also as sensing element, with high sensitivity and compact structure. Passive sensitive devices are resistant to electromagnetic interference and have wide frequency response. The system, with its special advantages, is widely used in structural monitoring, geotechnical engineering monitoring, military, oil and gas, aerospace, transportation and other fields.
According to different sensing principles, there are two types of systems: quasi distributed optical fiber monitoring system and distributed optical fiber monitoring system. One type is quasi distributed optical fiber monitoring system, which uses ultraviolet lithography to write gratings on the optical fiber. 100mm optical fiber contains 10000 regularly distributed small reflective mirrors in the core. Changes in external forces such as temperature, vibration, and ultrasound can cause linear changes in the grating spacing. The grating reflection wavelength changes linearly with the grating spacing, and the corresponding physical quantity changing parameters are obtained after demodulation of the wavelength.
Quasi distributed optical fiber monitoring system, which uses ultraviolet lithography to write gratings on the optical fiber. 100mm optical fiber contains 10000 regularly dis- tributed small reflective mirrors in the core. Changes in external forces such as temperature, vibration, and ultrasound can cause linear changes in the grating spacing. The grating reflection wavelength changes linearly with the gratingspac- ing, and the corresponding physical quantity changing parameters are obtained after demodulation of the wavelength.
Distributed optical fiber monitoring system, which generates small stress changes on the optical fiber when it is subjected to external sound or vibration, thereby stimulating the "coherent Rayleigh effect". DAS utilizes the small stress changes generated by sound vibration signals acting on optical fibers to alter the light passing through them. By demodulating these changes, the position, amplitude and frequency of sound events distributed on the optical fiber can be obtained, such as bearing failures.
·Long distance monitoring, with a monitoring distance of up to 40km;
·Strong anti-interference, the temperature measuring optical fiber is composed of quartz, electrically insulated, not affected by any electromagnetic interference, and does not emit electromagnetic waves, especially suitable for various complex and strong electrical environments;
·Intrinsically safe, the average power of the optical signal transmitted internally is at the micro watt level, indicating intrinsic safety;
·Accurate positioning, with positioning accuracy of ± 1m;
·Fast response, high sensitivity, swift reactive, and short single channel scanning time;
·Easy to install, the analyzer is easy to install, and the layout is flexible;
·Institute of Electrical Engineering, Chinese Academy of Sciences;
