What are DVS, DTS, DAS, FBG in fiber optic sensing

Principle of Distributed Fiber Optic Sensing Monitoring System

The propagation of light has a phenomenon called scattering.

scattering: When a light beam passes through an inhomogeneous medium, part of the beam will deviate from its original direction and spread out, and the light can be seen from the side, a phenomenon called light scattering.

Then the light scattering can be divided into elastic scattering and inelastic scattering. Inelastic scattering includes Brillouin scattering, Raman scattering, Compton scattering and so on. The distributed fiber optic sensing and monitoring system, on the other hand, is a product that uses different scattering implementations. There are based on Raman spectra (Raman spectra), Brillouin scattering, Rayleigh scattering, etc.

1. DVS zone type: is monitored by dividing the zone, and when a location invasion can not be accurately located to the specific location, only know in a certain zone, so the division of the zone is very important, we generally recommend 50m-200m a zone, the total zone is generally within 16. This will be able to quickly locate the location of the invasion (because the distance is relatively short). Mainly used in some civilian facilities, community buildings and other security projects around the session, the installation is more complex, can not be applied to long-distance transmission.

2. Distributed fiber optic vibration sensing system (DVS): measurement based on vibration, based on Rayleigh backward interference; positioning accuracy, and monitoring distance length are two more important indicators; the current leading level is about 40km, positioning accuracy of 5 meters, and even higher distances to 50KM, 60KM, higher distances such as 80KM is estimated to be a gimmick, may not be effective, or only laboratory data. Or only laboratory data. Compared with the anti-zone type, DVS can accurately locate the location of fiber optic disturbance, so the positioning accuracy is very important. Price is also slightly more expensive, the market price is estimated at 300,000-600,000 (CNY).

3. Distributed fiber optic acoustic monitoring system (DAS): acoustic monitoring, from the essence of the principle is also based on vibration measurement; the difference with DVS is that DAS for phase demodulation, can linearly restore the sound, DVS no phase mediation, can not restore the sound; now DAS is slowly becoming the mainstream of distributed fiber optic vibration measurement, in energy, oil, gas pipelines and other scenarios began to use.

4. Distributed fiber optic temperature measurement system (DTS): temperature measurement, the common DTS is generally based on Raman, the price is much cheaper, should be less than 100,000 yuan; there are also BOTDR based on Brillouin, the program can simultaneously measure temperature and stress, the site needs 2 fibers, a temperature measurement, a stress measurement, but the cost is very high, expensive prices can reach the million level.

5. fiber grating (FBG): fiber grating, optical filter etched inside the fiber, can filter out the light of a specific frequency. General engineering applications in a multi-channel FBG demodulation module, the back connected to FBG fiber sensor, measuring temperature, measuring stress, etc.; more mature, the disadvantage is that the cost is a little high, if you can bring down the cost of FBG application market is still quite a lot.